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  Selected Publications (English)


Kunisawa S, Ishida H, Ikai H, Nagano H, Fujiwara T, Ohdan H, Fujiwara Y, Tajima Y, Ueno T, Fujiwara Y, Shimada M, Suzuki Y, Watanabe Y, Hanazaki K, Kakeji Y, Kumamaru H, Takahashi A, Miyata H, Imanaka Y. Impact of the hospital volume and setting on postoperative complications of surgery for gastroenterological cancers in a regional area of Western Japan. Surgery Today 2022 (accepted) ; PMID: 35947194 ; DOI: 10.1007/s00595-022-02569-6 ; [鍵となる図]


・A research subgroup from the Japanese Society of Gastroenterological Surgery investigated incidences of perioperative complications of ≥Grade 3 of the Clavien-Dindo classification after gastroenterological surgery and the association of hospital characteristics, which are defined using a combination of hospital case-volume and patients’ hospital travel distance.
・With the Japanese National Clinical Database, we investigated 4 proceduares; distal gastrectomy for gastric cancer (outcome incidence 5.6%),total gastrectomy for gastric cancer (10.2%), right hemicolectomy for colon cancer (5.5%), lower anterior resection for rectal cancer (10.7%) , and after adjusting for backgrounds, no association was determined between the hospital characteristics and the outcome.
・Our study results did not provide positive support for the consolidation and centralization of hospitals based solely on hospital case volume, at least in the Chushikoku region.

Takahashi H, Terada I, Higuchi T, Takada D, Shin J , Kunisawa S, Imanaka Y. The relationship between new PCR positive cases and going out in public during the COVID-19 epidemic in Japan. PLOS ONE 2022 May 26;17(5):e0266342 ; PMID: 35617292 ; DOI: 10.1371/journal.pone.0266342 ; [鍵となる図] ; [Key Figure]


・We analyzed the relationship between the number of new PCR positive cases and four indicators of people going out in public during the first and second waves of the COVID-19 in Japan on publicly available data using cross-correlation analysis.
・Comparison of the same indicator between the first and second waves showed different lags and directions of change, and comparisons between each outgoing indicator showed greater differences among indicators in the second wave than in the first wave.
・The complexity of people's behavior regarding going out increased during the second wave when the new policy was implemented, suggesting that the policy may have affected people's mobility more than the number of new PCR positive cases.

Tsutsumi T, Ishibashi M, Takemura M, Isashiki S, Niwa R, Imanaka Y. Quantification of internal medicine resident inpatient care using Diagnosis Procedure Combination database. Internal Medicine 2022 May 21; Epub ahead of print. ; PMID: 35598990 ; DOI: 10.2169/internalmedicine.8726-21


・DPC-based quantification of patient encounters during internal medicine residency training is effective in evaluating the coverage of the current J-OSLER list.
・Owing to its wide availability and generalization, this method could be used as a universal tool in assessment of internal medicine programs.

Morishita T, Takada D, Shin J, Higuchi T, Kunisawa S, Fushimi K, Imanaka Y. Effects of the COVID-19 pandemic on heart failure hospitalizations in Japan: interrupted Time Series Analysis. ESC Heart Failure 2022 9(1):31-38 ; PMID: 34913269 ; DOI: 10.1002/ehf2.13744 ; [鍵となる図] ; [Key Figure]


・Using DPC data, we examined the impact of the declaration of a state of emergency on heart failure admission in Japan.
・There was a statistically significant decrease in the number of hospitalizations for heart failure immediately after the declaration of a state of emergency by using interrupted time series analyses.
・The proportion of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers prescriptions did not change before or after the declaration of the emergency.
・In-hospital crude mortality rates also did not worsen before or after the declaration of an emergency.

Nagano H, Shin J, Morishita T, Takada D, Kunisawa S, Fushimi K, Imanaka Y. Hospitalization for ischemic stroke was affected more in independent cases than in dependent cases during the COVID-19 pandemic: an interrupted time series analysis. PLOS ONE 2021 Dec 17;16(12):e0261587 ; PMID: 34919571 ; DOI: 10.1371/journal.pone.0261587 ; [鍵となる図] ; [Key Figure]


・We analyzed the impact of the first wave of COVID-19 on the number of hospitalized patients with ischemic stroke on DPC database using interrupted time-series (ITS) analysis.
・The ITS analysis showed a significant decrease in the number of ischemic stroke cases hospitalized. The proportion of decline in the independent group was larger than that in the dependent group.
・The ITS analysis showed that there was no significant change in the proportions of inpatient cases receiving intravenous thrombolysis and endovascular intervention.

Okuno T, Itoshima H, Shin J, Morishita T, Kunisawa S, Imanaka Y. Physical restraint of dementia patients in acute care hospitals during the COVID-19 pandemic: A cohort analysis in Japan. PLOS ONE 2021 Nov 22;16(11):e0260446 ; PMID: 34807945 ; DOI: 10.1371/journal.pone.0260446 ; [鍵となる図] ; [Key Figure]


・We evaluated the impact of changes due to the COVID-19 pandemic on physical restraint among elderly patients with cognitive impairment in acute care hospitals using the QIP database.
・The ITS analysis showed an increase in the rate of physical restraint use in hospitals received COVID-19 positive patients.
・Medical staff especially working for hospitals received the Covid 19 positive patients were under pressure owing to the heavy workload, higher risk of infection and prejudice, which may affect our results.

Watanabe S, Shin J, Morishita T, Takada D, Kunisawa S, Imanaka Y. Medium-term impact of the epidemic of the coronavirus disease 2019 on the practice of percutaneous coronary interventions in Japan. Journal of Atherosclerosis and Thrombosis 2021 Dec 18. Epub ahead of print ; PMID: 34924456 ; DOI: 10.5551/jat.63194 ; [鍵となる図]


・DPC data from QIP database were analyzed to clarify the medium term impact of the COVID-19 epidemic on practice of PCIs in Japan.
・The COVID-19's impacts on volumes of PCIs were larger in the first surge than the subsequent, larger in the elective than in the emergency, and continued for approximately one year after the emergence of the epidemic.
・During the epidemic of the COVID-19, in-hospital mortality of cases undertaking emergency PCIs did not change.

Tsutsumi I, Tsutsumi Y, Yoshida C, Komeno T, Imanaka Y. Impact of the Clinical Trials Act on noncommercial clinical research in Japan: An interrupted time-series analysis. Journal of Epidemiology 2022 Jan 5;32(1):27-33 ; PMID: 34690242 ; DOI: 10.2188/jea.JE20210051 ; [鍵となる図] ; [Key Figure]


・We used publicly available data from the University Hospital Medical Information Network (UMIN-CTR), a clinical research registry, to examine the impact of the Clinical Trials Act (CTA) implementation on the number of new clinical studies using an interrupted time-series analysis (ITSA) approach.
・The rate of change in the number of new clinical studies per month decreased significantly in the first year after the CTA enforcement compared to the period before the CTA enforcement. There was also a significant decrease in the number of monthly studies immediately after the CTA was enacted.
・Analyses using the multigroup ITSA showed that the rate of decline in the monthly number of new studies was particularly large for studies with small sample sizes, intervention studies, and studies with nonprofit funding sources. It was suggested that studies with less human and financial support may have been more affected by the Clinical Research Act.

Mukai T, Tsutsumi T, Takaishi E, Hamada O, Sasaki S, Shimokawa T, Imanaka Y. Nurse Practitioner's Geriatric Practice in Japanese Postacute Care Setting. The Journal for Nurse Practitioners 2021 17(10):1250-1255 ; DOI: 10.1016/j.nurpra.2021.08.002

・診療看護師(Nurse Practitioner:NP)の導入の影響を前向き観察研究で評価した。

・The quality of comprehensive geriatric assessment and medication reconciliation by a nurse practitioner (NP) based in Japan was evaluated by a prospective observational study.
・NPs were suggested to have benefits toward geriatric care that may allow for much-needed task shifting in Japan.

Kishimoto K, Kunisawa S, Fushimi K, Imanaka Y. Individual and nationwide costs for cancer care during the first year after diagnosis among children, adolescents, and young adults in Japan. JCO Oncology Practice 2021 Sep 27:OP2100364. Epub ahead of print ; PMID: 34570620 ; DOI: 10.1200/OP.21.00364 ; [鍵となる図] ; [Key Figure]

・成人がんの既報(年間医療費 前立腺がん 平均739,147円、子宮頚がん 平均474,756円)と比較し、我が国における小児・AYAがんの診断後1年間患者1人当たり医療費は高額であり、小児(平均 10,029,310円、中央値 8,325,420円、四分位範囲 2,475,160 - 16,690,510円)がAYA(平均 4,089,087円、中央値 1,865,350円、四分位範囲 795,390 - 4,765,085円)より高かった。
・小児・AYAがん患者の診断後1年間国内総医療費は 348.3億円(95%信頼区間 250.8 - 445.7億円)と推計された。

<Individual and nationwide costs for cancer care during the first year after diagnosis among children, adolescents, and young adults (AYAs) in Japan were estimated as a foundation for economic evaluation and health policy planning.>
・Cancer is one of the leading causes of death among younger age groups, and the burden of cancer in young age groups has been reported to be remarkably high.
・The 1-year individual cost was higher in children (mean 10,029,310, median 8,325,420, IQR 2,475,160 to 16,690,510 JPY) than in AYAs (mean 4,089,087, median 1,865,350, IQR 795,390 to 4,765,085 JPY), and these costs were markedly higher than recently reported annual cancer care costs in Japanese adult patients (prostate cancer, mean 739,147 JPY; cervical cancer, mean 474,756 JPY).
・The 1-year nationwide cost after diagnosis was estimated as 34.83×109 (95% CI 25.08×109 to 44.57×109) JPY.

Kohori-Segawa H, Uematsu H, Dorji N, Wangdi U, Dorjee C, Yangchen P, Kunisawa S, Sakamoto R, Imanaka Y. Gender with marital status, cultural differences, and vulnerability to hypertension: Findings from the national survey for noncommunicable disease risk factors and mental health using WHO STEPS in Bhutan. PLOS ONE 2021 Vol.16 Issue 8 Pages e0256811 ; PMID: 34464428 ; DOI: 10.1371/journal.pone.0256811


・Women had a higher odds ratio than men when married, and when separated, divorced, or widowed.
・People who speak the Tshanglakha language scored the highest odds, Lhotshampakha was higher than Dzongkha after adjusting for various social and biomedical factors.
・Tobacco use displayed decreased odds for hypertension.
・To promote the early detection and prevention of hypertension, cultural factors also should be considered even within small geographic areas, such as Bhutan.

Umegaki T, Kunisawa S, Nishimoto K, Nakajima Y, Kamibayashi T, Imanaka Y. Paraplegia after open surgical repair vs thoracic endovascular aortic repair for thoracic aortic disease: a retrospective analysis of Japanese administrative data. Journal of Cardiothoracic and Vascular Anesthesia 2021 Jul 30:S1053-0770(21)00624-8 ; PMID: 34446324 ; DOI: 10.1053/j.jvca.2021.07.043

・胸部大動脈疾患に対する開心術と血管内治療 (TEVAR) の術後対麻痺についてQuality Indicator/Improvement Project (QIP) における多施設のDPCデータベースを用いて評価した.
・術後対麻痺の発生率は開心術で3.0%, TEVARで2.3%であった (P=0.36). 開心術に対するTEVARのオッズ比は逆数重み付け法で0.81 (95%信頼区間: 0.42-1.59) , 操作変数法で0.88 (0.42-1.86) であった.
・胸部大動脈疾患に対する開心術と血管内治療 (TEVAR) で術後対麻痺の発生率の差はみとめなかった.

・For this study, data were acquired from a DPC database containing clinical information and administrative data routinely collected from participating hospitals by the Quality Indicator/Improvement Project (QIP).
・We comparatively assessed the postoperative paraplegia risk between open surgical repair and TEVAR in patients with thoracic aortic disease.
・The incidence of postoperative paraplegia was similar between the groups (open surgical repair group: 3.0%; TEVAR group: 2.3%; P = 0.36). The odds ratios of paraplegia for TEVAR (relative to open surgical descending aortic repair) were 0.81 (95% confidence interval: 0.42-1.59) in the inverse probability of treatment weighted-model and 0.88 (0.42-1.86) in the instrumental variable model
・There were no statistical differences in the risk of paraplegia between open surgical repair and TEVAR in thoracic aortic disease patients.

Shin J, Lin H, Imanaka Y. COVID-19 Impact on the Japanese Healthcare System and Comparison of its Countermeasures With South Korea and Taiwan. IJQHC Communications 2021 1(1):lyab008 ; DOI: 10.1093/ijcoms/lyab008


・Asian countries had generally controlled the pandemic better than other countries.
・The number of COVID-19 cases is comparatively low in Japan, our studies show the impact is significant.
・Japanese measures were less strict, less prompt, and less comprehensive compared to those of South Korea and Taiwan, and heavily relied on people's self-restraint.

Bun S, Kishimoto K, Shin J, Maekawa T, Takada D, Morishita T, Kunisawa S, Imanaka Y. Impact of the COVID-19 pandemic on asthma exacerbations in children: a multi-center survey using an administrative database in Japan. Allergology International 2021 Oct;70(4):489-491 ; PMID: 34281768 ; DOI: 10.1016/j.alit.2021.06.001 ; [鍵となる図] ; [Key Figure]


Our data demonstrated 1) a dramatic decrease in pediatric patients with asthma exacerbations who required hospital admission, and 2) a decrease in the prescription of inhaler solutions during hospitalization during the COVID-19 pandemic.

Charani E, McKee M, Ahmad R, Balasegaram M, Bonaconsa C, Merrett GB, Busse R, Carter V, Castro-Sanchez E, Franklin BD, Georgiou P, Hill-Cawthorne K, Hope W, Imanaka Y, Kambugu A, Leather AJ, Mbamalu O, McLeod M, Mendelson M, Mpundu M, Rawson TM, Ricciardi W, Rodriguez-Manzano J, Singh S, Tsioutis C, Uchea C, Zhu N, Holmes AH. Optimising antimicrobial use in humans – review of current evidence and an interdisciplinary consensus on key priorities for research. Lancet Regional Health Europe 2021 Jun 29;7:100161 ; PMID: 34557847 ; DOI: 10.1016/j.lanepe.2021.100161


・The pandemic of antimicrobial resistance (AMR) is a focus of the 2021 G7 meeting.
・We need to balance AMR research efforts between development of new agents and strategies to preserve the efficacy and maximise effectiveness of existing agents.
・We identified research priorities for optimising antimicrobial use in humans across four broad themes: policy and strategic planning; medicines management and prescribing systems; technology to optimise prescribing; and context, culture and behaviours.

Itoshima H, Shin J, Takada D, Morishita T , Kunisawa S, Imanaka Y. The impact of the COVID-19 epidemic on hospital admissions for alcohol-related liver disease and pancreatitis in Japan. Scientific Reports 2021 11(1):14054 ; PMID: 34253741 ; DOI: 10.1038/s41598-021-92612-2 ; [鍵となる図] ; [Key Figure]


・We found that the rate of admissions per 1,000 admissions during the COVID-19 epidemic period (April 2020 to June 2020) was 1.2 times compared to the pre-epidemic period (July 2018 to March 2020) by using QIP project database.
・Analyses stratified by sex revealed that the increases in admission rates of alcohol-related liver disease or pancreatitis for females were higher than for males during the COVID-19 epidemic period.
・During the COVID-19 epidemic, we should pay attention to the problem of harmful alcohol consumption.

Teraoka E, Kunisawa S, Imanaka Y. Trajectories of end-of-life medical and long-term care expenditures for older adults in Japan: retrospective longitudinal study using a large-scale linked database of medical and long-term care claims. BMC Geriatrics 2021 30;21(1):403 ; PMID: 34193081 ; DOI: 10.1186/s12877-021-02215-9


We analyzed trajectories of medical and long-term care expenditures and their sum of 16,084 individual cases during the 60 months before the date of death. We identified six distinct spending trajectories for the total care expenditures. Factors associated with the high-persistent trajectory were chronic illnesses, various organ failures, neurodegenerative diseases, fractures, and tube feeding. This finding has implications for improving the quality of end-of-life care and its financial foundation.

Nagano H, Takada D, Shin J, Morishita T, Kunisawa S, Imanaka Y. Hospitalization of mild cases of community-acquired pneumonia decreased more than severe cases during the COVID-19 pandemic. International Journal of Infectious Diseases 2021 May; 106: 323–328. ; PMID: 33794382 ; DOI: 10.1016/j.ijid.2021.03.074 ; [鍵となる図] ; [Key Figure]

日本のおける市中肺炎の入院患者数と重症度に対するCOVID-19流行の影響をDPCデータを用いて分析した。COVID-19流行時(2020年3-7月)に市中肺炎の入院患者は前年度と比較し-45.2%と大きく減少した一方で、緊急入院は一時的な減少にとどまった。A-DROPで重症度別に分析すると、軽症例で入院数の前年度比の減少は大きかった(軽症 -55.2%, 中等症 -45.8%, 重症 -39.4%, 超重症 -33.2% )

Based on administrative claims data, we evaluated the impact of the COVID-19 epidemic on the number and severity of inpatients for CAP in Japan. During the COVID-19 epidemic (between March and July 2020), the number of inpatient cases for CAP drastically decreased during the epidemic compared with the same period in the past year (-45.2%), despite only a temporary reduction in the number of other urgent admissions. According to the severity score “A-DROP”, milder cases showed a greater decrease in the year-over-year ratio than severe ones (mild -55.2%, moderate -45.8%, severe -39.4%, and extremely severe -33.2%).

Kishimoto K, Bun S, Shin J, Takada D, Morishita T, Kunisawa S, Imanaka Y. Early impact of school closure and social distancing for COVID-19 on the number of inpatients with childhood non-COVID-19 acute infections in Japan. European Journal of Pediatrics 2021 Sep;180(9):2871-2878 ; PMID: 33791861 ; DOI: 10.1007/s00431-021-04043-w ; [鍵となる図] ; [Key Figure]


Based on administrative claims data, we confirmed a marked reduction in the number of inpatients for childhood non-COVID-19 acute infections in the post-school-closure period (March – June 2020) in Japan. The main part of the reduction was for pre-school children, particularly in respiratory infection and gastrointestinal infection groups.

Okuno T, Takada D, Shin J, Morishita T, Itoshima H, Kunisawa S, Imanaka Y. Surgical volume reduction and announcement of triage during the 1st wave of the covid-19 pandemic in Japan: a cohort study using interrupted time series analysis. Surgery Today 2021 21:1–8 ; PMID: 33881619 ; DOI: 10.1007/s00595-021-02286-6 ; [鍵となる図] ; [Key Figure]

新型コロナウイルス感染症(COVID-19)のパンデミックを受けて,日本の各外科学会は手術トリアージを表明した。 本研究では、手術トリアージ声明が、COVID-19第 1 波における予定手術の減少に影響を与えたかどうかを明らかにすることを目的とした。 2018 年 7 月 1 日から 2020 年 6 月 30 日までの間に予定入院で主要な手術を受けた490,719 症例を抽出した。 手術の分類をした後、分時系列解析(ITS)を実施し、トリアージ声明による各手術症例数の減少への影響を検証した。 ITS解析の結果、日本の各外科学会の声明に基づき、トリアージ優先度の低い手術では検定上有意な症例数の減少を認めた。

Each surgical society stated surgical triage because of the Coronavirus Disease (COVID-19) pandemic. We aimed to identify whether the announcement of surgical priorities by each Japanese surgical society affected the surgical volume decline during the 1st wave of this pandemic. We extracted 490,719 available cases of patients who had elective major surgeries between July 1, 2018, and June 30, 2020. After categorization of surgical specialties, we conducted an interrupted time series analysis (ITS) to validate the decline of each surgical procedure. The ITS analysis showed that non-critical surgeries showed obvious and statistically significant declines in case volume during the 1st wave of the COVID-19 pandemic based on the statement of each surgical society in Japan.

Morishita T, Takada D, Shin J, Higuchi T, Kunisawa S, Imanaka Y. Trends, Treatment Approaches, and In-Hospital mortality for Acute Coronary Syndrome in Japan During the Coronavirus Disease 2019 Pandemic. Journal of Atherosclerosis and Thrombosis 2021 Apr 1. Epub ahead of print ; PMID: 33790127 ; DOI: 10.5551/jat.62746


We examined the impact of the declaration of a state of emergency on the treatment of acute coronary syndromes in Japan. There was a statistically significant decrease in the number of hospitalizations for acute coronary syndromes (acute myocardial infarction and unstable angina) immediately after the declaration of a state of emergency by using interrupted time series analyses. The rates of percutaneous coronary intervention, coronary artery bypass graft surgery, and fibrinolysis for acute coronary syndromes did not change before or after the declaration of the emergency. In-hospital crude mortality rates also did not worsen before or after the declaration of an emergency. The risk-adjusted logistic regression analysis also confirmed that the COVID-19 pandemic did not affect the in-hospital mortality.

Shin J, Mizuno S, Okuno T, Itoshima H, Sasaki N, KunisawaS, Kaku M, Yoshida M, Gu Y, Morii D, Shibayama K, Ohmagari N, Imanaka Y. Nationwide multicenter questionnaire surveys on countermeasures against antimicrobial resistance and infections in hospitals. BMC Infectious Diseases 2021 21:234 ; PMID: 33639873 ; DOI: 10.1186/s12879-021-05921-2

医療機関における病院感染対策の全体像を把握するため、2015 年時点の基幹型臨床研修病院( n=1,017 )を対象とし、調査票調査を行った。調査票調査は、年次変化についても評価するため、約 1 年の間隔で 2 回( 1 回目: 2016 年 11 月、 2 回目: 2018 年 2 月)実施した。回答病院(1回目: 683 病院、2回目:563 病院)の中、感染制御チーム(ICT )の活動が行われている病院は 99% を超えていたが、その活動内容には病院により差があり、「抗菌薬が開始された患者に対する介入基準が定められている」病院は約 7 割、抗 MRSA 薬と広域抗菌薬の使用基準がある病院はそれぞれ約 6 割、 5 割に留まっていた。サーベイランスは、手術部位感染や中心静脈カテーテル関連血流感染に対しては約 7 割の病院が行っていたが、カテーテル関連尿路感染のサーベイランスの実施割合は約 5 割、人工呼吸器関連肺炎のサーベイランスの実施は約 4 割に留まっていた。

We posted questionnaires to all teaching hospitals (n=1017) regarding hospital countermeasures against AMR and infections. To evaluate changes over time, surveys wereconducted twice (1st survey: Nov 2016, 2nd survey: Feb 2018). A latent transition analysis (LTA) was performed to identify latent statuses, which refer to underlying subgroups of hospitals. The number of valid responses was 678 (response rate, 55.0%) for the 1st survey and 437 (43.0%) for the 2nd survey. More than 99% of participating hospitals had infection control teams, with differences in activity among hospitals. Roughly70% had their own intervention criteria for antibiotics therapies, whereas only about 60% and 50% had criteria established for the use of anti-methicillin-resistant Staphylococcus aureus antibiotics and broad-spectrum antibiotics, respectively. Only 50% and 40% of hospitals conducted surveillance of catheter-associated urinary tract infections and ventilator-associatedpneumonia, respectively. Results of the LTA did not support a relationship between increasing the number of infection control practitioners per bed, whichis reportedly related to improvements in antimicrobial stewardship, and being in more favorable latent statuses.

Okuno T, Kunisawa S, Fushimi K, Imanaka Y. Intra-operative autologous blood donation for cardiovascular surgeries in Japan: a retrospective cohort study. PLOS ONE 2021 16(3):e0247282. ; PMID: 33690678 ; DOI: 10.1371/journal.pone.0247282 ; [鍵となる図] ; [Key Figure]


Large volume intra-operative autologous blood donation (IAD) is difficult to perform for Japanese patients, who are physically small. We evaluated the association between IAD and decrease in perioperative transfusion in cardiovascular surgery using a Japanese administrative database. We enrolled 32,433 and 4,267 patients who underwent cardiac and aortic surgeries. Multilevel propensity score matching showed that IAD could reduce the transfusion rate or amount of red blood cells for Japanese patients, even when the IAD volume was not large.

Shin J, Takada D, Kunisawa S, Imanaka Y. Effects of periodontal management for patients with type 2 diabetes on healthcare expenditure, hospitalization, and worsening of diabetes: an observational study using medical, dental, and pharmacy claims data in Japan. Journal of Clinical Periodontology. 2021 Jun;48(6):774-784 ; PMID: 33544396 ; DOI: 10.1111/jcpe.13441

某県の国民健康保険・後期高齢者医療制度レセプトデータ(医科・歯科・調剤)から、2015年度に糖尿病薬の処方のある35歳以上の患者の歯周疾患の管理有無および医療費、入院有無を3年間観察した。解析対象患者は、16,583人で、歯周疾患の管理を2年間毎年1回以上行った患者は、管理を受けなかった患者より3年目の医療費が4%減少(adjusted multiplier 0.96, 95% CI: 0.92–1.00)、3年目の入院が10%減少した(aOR 0.90, 95% CI: 0.82–0.98)。観察期間の1~2年目にインスリン投与のなかった13,222人を対象とした解析では、2年間毎年1回以上の歯周疾患管理を受けた患者において3年目にインスリン投与の開始が23%減少した(aOR0.77, 95% CI: 0.64–0.92)。

We collected data of individuals who were prescribed diabetes medications during the fiscal year 2015 from the claims database of a prefecture in Japan. The results of the 3-year follow-up showed that the annual healthcare expenditure in the third yearwas 4% less (adjusted multiplier 0.96, 95% confidence interval [CI] 0.92–1.00) in the group receiving periodontal management every year. The adjusted odds ratio (aOR) for all-cause hospitalization was 0.90 (95% CI: 0.82–0.98). The aOR of introducing insulinin the third year for those who had not been prescribed insulin during the previous two years (n=13,222) was 0.77 (95% CI: 0.64–0.92) in the group receiving periodontal management every year.

Okuno T, Takada D, Shin J, Morishita T, Itoshima H, Kunisawa S, Imanaka Y. Impact of the early stage of the coronavirus disease 2019 pandemic on surgical volume in Japan. British Journal of Surgery 2021 znab028,13 February ; PMID: 33793774 ; DOI: /10.1093/bjs/znab028 ; [鍵となる図] ; [Key Figure]

COVID-19の感染拡大早期における、日本の予定手術件数を前年度比で算出した。8診療科区分のうち、いずれも4月から減少し5月で最低値となり、特に眼科(全年度比52.1%)と耳鼻咽喉科(28.1%) で減少率が大きかった。今後の感染拡大も考慮しつつ、積み残し手術をいかに処理していくかが肝要である。

The year-over-year trend of scheduled surgeries in Japan during the early stage of the COVID-19 pandemic was calculated. All eight surgical categories, especially ophthalmologic and ear/nose/throat (ENT) surgeries, decreased from April 2020 and reached a minimum in May 2020 (ophthalmologic, 52.1%; ear/nose/throat, 28.1%). It is important to take into account the spread of infection in the future and how to deal with backlog surgeries.

Takada D, Kunisawa S, Imanaka Y. Stages of a transtheoretical model as predictors for the decline of estimated glomerular filtration rate: a retrospective cohort study. Journal of Epidemiology 2021 (accepted) ; PMID: 33487611 ; DOI: 10.2188/jea.JE20200422

・ステージが高い集団は翌年の健康行動の改善割合が高く、年齢性別などの他に糖尿病や高血圧や脂質代謝異常症などで調整しても、有意に腎機能低下 (eGFR30%以上の低下)のリスクを軽減した。

Compared with the risk associated with the precontemplation stage (stage 1), the preparation, action, and maintenance stages (stages 3, 4, and 5), were associated with a lower risk of eGFR decline.It is not enough to "know" what health actions one should take (there is no significant difference compared to those who are indifferent), but if one "can imagine what actions he should take in the future," it is possible to delay the subsequent decline in kidney function.

Becker CB, Taniyama Y, Kondo-Arita M, Sasaki N, Yamada S, Yamamoto K. Unexpected costs of bereavement grief in Japan: Patterns of increased use of medical, pharmaceutical and financial services. OMEGA - Journal of Death and Dying 2021 Feb 2;30222821992193 ; PMID: 33530889 ; DOI: 10.1177/0030222821992193


Our Japan-wide survey (n=1,078) revealed that bereaved who showed increased reliance on medical, pharmaceutical, and financial/legal services was in the ‘50’s age bracket, and for unemployed widows; it corresponded less with low annual income than with high income. Increased users reported their decline in physical health seriously influencing their work and lives, suggesting “presenteeism”. Moreover, they spent 2.7 times more for medical and pharmaceutical services than those reporting continual use, portending 4 to 10 times more Japanese government expense for this group, half of whom considered their own out-of-pocket expenses a financial burden.

Shin J, Takada D, Morishita T, Lin H, Bun S, Teraoka E, Okuno T, Itoshima H, Nagano H, Kishimoto K, Segawa H, Asami Y, Higuchi T, Minato K, Kunisawa S, Imanaka Y. Economic impact of the first wave of the COVID-19 pandemic on acute care hospitals in Japan. Plos One 2020 15(12):e0244852 ; PMID: 33382838 ; DOI: 10.1371/journal.pone.0244852

QIP参加病院の2年間(2018年7月~2020年6月)のデータの解析結果、前年同月と比べ、医療費収入(入院+外来)が2020年4, 5, 6月に7%, 14%, 5%減少した。2020年度4~5月の医療費を目的変数とし、2020年3月までの平均医療費、COVID-19確定・疑い患者の在院日数を説明変数とした回帰分析の結果、全病院において平均6.3%の医療費の減少を認めた。さらに、COVID-19確定患者の在院日数1日当たり、2020年4~5月の医療費327,000円の減少を認め、COVID-19患者受け入れ病院の医療費減少がより大きいことが示唆された。

We analyzed DPC data between July 2018 and June 2020. In percentage terms, claimed hospital charges, which included both inpatients and outpatients, for April, May, and June 2020 decreased by 7%, 14%, and 5%, respectively, compared to the same months in 2019. The result of the regression analysis showed that the claimed charges for hospitals with COVID-19 patients decreased by an additional 327,000 JPY per day of stay for confirmed COVID-19 patients compared to hospitals without COVID-19 patients. It is suggested that hospitals caring for COVID-19 patients were negatively incentivized.

Otokita S*, Uematsu H*, Kunisawa S, Sasaki N, Fushimi K, Imanaka Y. Impact of rehabilitation start time on functional outcomes after stroke. Journal of Rehabilitation Medicine 2020 Epub ahead of print [*:equal contribution] ; PMID: 33284355 ; DOI: 10.2340/16501977-2775


This study analyzed the impact of rehabilitation start time after stroke in acute hospitals using DPC data. Starting post-stroke rehabilitation on the day of admission or second day of hospitalization may be the optimum timing for functional outcomes.

Sasaki N, Yamaguchi N, Okumura A, Yoshida M, Sugawara H, Shin J, Kunisawa S, Imanaka Y. Factors affecting the use of clinical practice guidelines by hospital physicians : the interplay of IT infrastructure and physician attitudes. Implementation Science 2020 15(1):101 ; PMID: 33239076 ; DOI: 10.1186/s13012-020-01056-1


This study revealed that physicians’ habitual attitudes, CPG-related education and a combination of individual digital preference and superior hospital IT circumstances, is key to bridging the gap between the use and implementation of CPGs.

Naylor NR, Yamashita K, Iwami M, Kunisawa S, Mizuno S, Castro-Sánchez E, Imanaka Y, Ahmad R, Holmes A. Code-sharing in cost-of-illness calculations: an application to antibiotic-resistant bloodstream infections. Frontiers in Public Health 2020 Nov 27;8:562427 ; PMID: 33330310 ; DOI: 10.3389/fpubh.2020.562427

Groenewoud S, Sasaki N, Westert GP, Imanaka Y. Preferences in end of life care substantially differ between the Netherlands and Japan. Medicine. 2020 99 (44):e22743,October 30 ; PMID: 33126312 ; DOI: 10.1097/MD.0000000000022743

終末期医療に関する市民の意思について、日本とオランダを比較調査した。日本人は将来の依存状態について考えることを避ける傾向があり、また終末期の自分は周囲の重荷になると考え、死に場所として病院を好む傾向を認めた。一方、オランダ人は主治医が積極的に終末期に関するアプローチを行うことを好む傾向が強かった。Shared decision makingやAdvanced Care Planningを行う際には、このような国際的な価値観・嗜好の違いを考慮に入れる必要がある。

Preferences in the end-of-life (EoL) care substantially differ between the Netherlands and Japan. These differences should be taken into account a) when interpreting geographical variation in EoL care, and b) if strategies such as shared decision making or advanced care planning – are considered.

Braithwaite J , Vincent C, Garcia-Elorrio E, Imanaka Y, Nicklin W, Sodzi-Tettey S, Bates D. Transformational improvement in quality care and health systems: the next decade. BMC Medicine 2020 Oct 29;18(1):340 ; PMID: 33115453 ; DOI: 10.1186/s12916-020-01739-y

Shin J, Kunisawa S, Imanaka Y. New outcome-specific comorbidity scores excelled in predicting in-hospital mortality and healthcare charges in administrative databases. Journal of Clinical Epidemiology 2020 Oct;126:141-153. ; PMID: 32540387 ; DOI: 10.1016/j.jclinepi.2020.06.011

DPCデータを使って新しく算出した重みを用いた併存症指数がCharlson comorbidity indexなどの既存の方法より優秀なパフォーマンスを示した。また、死亡の予測のために開発された併存症指数は医療費や在院日数の予測においては併存症の影響を十分に調整できなかった。そこで、併存症指数の開発に用いた集団と異なる集団、アウトカムと異なる研究のためには、併存症指数を構成する重みの再算出または最新の重みの採用を検討する必要がある。

The comorbidity scores using the new weights derived from a Japanese inpatient database outperformed previous measures, such as the Charlson comorbidity index. The comorbidity scores developed for predicting mortality could not adjust comorbidity burdens thoroughly in models for predicting hospital charges and length of hospital stay. Thus, for different study populations and outcomes, researchers should consider updating them or adopting the newer weights available.

Uematsu H, Yamashita K, Kunisawa S, Imanaka Y. Prediction Model for Prolonged Length of Stay in Patients with Community-Acquired Pneumonia Based on Japanese Administrative Data. Respiratory Investigation 2020 194-203 ; DOI: 10.1016/j.resinv.2020.08.005

304の急性期病院DPCデータを用いて市中肺炎における在院日数遷延化予測モデルの構築検証を行った。遷延化に関連する有意な要因は年齢・ADL・FiO2・JCS・貧血等であり、C統計量は0.78(95%CI 0.77-0.98)であった。本研究の予測モデルは肺炎の在院日数遷延化のハイリスク患者を同定し適切な入院管理を行う上で有用であると考えられた。

The development and validation of prediction models of prolonged length of stay in community-acquired pneumonia was performed using administrative data from 304 acute care hospitals in Japan. Significant factors associated with prolongation were age, ADL, FiO2, JCS, anemia, etc. with C-statistic of 0.78 (95% CI 0.77-0.98). Our prediction model was considered useful in identifying patients at high risk of prolonged length of stay and appropriate hospitalization management.

Kohori-Segawa H, Dorji C, Dorji K, Wangdi U, Dema C, Dorji Y, Musumari PM, Techasrivichien T, Sugimoto-Watanabe SP, Sakamoto R, Ono-Kihara M, Kihara M, Imanaka Y. A qualitative study on knowledge, perception, and practice related to non-communicable diseases in relation to happiness among rural and urban residents in Bhutan. PLOS ONE 2020 (2020 June 29) 15(6): e0234257 ; PMID: 32598347 ; DOI: 10.1371/journal.pone.0234257 ; [鍵となる図]


This is the first comprehensive qualitative study on the NCD-related lifestyle risks among Bhutanese concerning the concept of happiness. Research was conducted in rural and urban communities of Bhutan in 2017 among 79 inhabitants of both genders, aged ≥18. The data was collected by in-depth interviews, participatory observation, photo documentation, and anthropometric measurements. From these observations, it is recommended that more practical NCD education/prevention programs should be urgently introduced in Bhutan that involve multiple generations, religion authorities, educational settings, and medical services.

Takada D, Kunisawa S, Matsubara T, Fushimi K, Yanagita M, Imanaka Y. Developing and validating a multivariable prediction model for in-hospital mortality of pneumonia with advanced chronic kidney disease patients: a retrospective analysis using a nationwide database in Japan. Clinical and Experimental Nephrology 2020 Aug;24(8):715-724 ; PMID: 32297153 ; DOI: 10.1007/s10157-020-01887-8


Seven variables were selected, which includes age (male ≥ 70 years, female ≥ 75 years), respiratory failure, orientation disturbance, low blood pressure, the need of assistance in feeding or bowel control, severe or moderate thinness and CRP 200 mg/L or extent of consolidation on chest X-ray ≥2/3 of one lung. The c-statistics of univariate logistic regression for in-hospital mortality of pneumonia with advanced chronic kidney disease patients was 0.8017 using seven variables, while that was 0.7372 using “A-DROP”

Takahashi T, Otsubo T, Kunisawa S, Sasaki N, Imanaka Y. Factors associated with high-dose antipsychotic prescriptions in outpatients with schizophrenia: An analysis of claims data from a Japanese prefecture. Neuropsychopharmacology Reports 2020 Sep;40(3):224-231 ; PMID: 32452649 ; DOI: 10.1002/npr2.12109


This study focused on high-dose antipsychotic prescriptions in outpatients with schizophrenia using claims data, and aimed to identify their correlates. High-dose antipsychotics were associated with anxiolytics/hypnotics, mood stabilizers, prescription by non-psychiatrists, and were strongly associated with anti-Parkinson's agents. It was suggested that the adjustment of anti-Parkinson's agents and the approach to non-psychiatrists are important with regard to reduction of high-dose antipsychotic prescriptions.

Hirota Y, Kunisawa S, Fushimi K, Imanaka Y. Association between clinic physician workforce and avoidable readmission: a retrospective database research. BMC Health Services Research 2020 ;20(1):125. ; PMID: 32070343 ; DOI: 10.1186/s12913-020-4966-4 ; [鍵となる図] ; [Key Figure]


This study aimed to examine the relationship between clinic physician workforce and unplanned readmission for ambulatory care sensitive conditions (ACSCs). We found that in patients who had history of admision for ACSCs, larger clinic physician workforce prevented the occurrence of readmission for ACSCs.

Umegaki T, Kunisawa S, Nishimoto K, Kamibayashi T, Imanaka Y. Effectiveness of combined antithrombin and thrombomodulin therapy on in-hospital mortality in mechanically ventilated septic patients with disseminated intravascular coagulation. Scientific Reports 2020 Mar 17;10(1):4874 ; PMID: 32184456 ; DOI: 10.1038/s41598-020-61809-2

本邦ではアンチトロンビン製剤 (AT) やリコンビナントトロンボモデュリン (TM) は敗血症性DIC症例に広く利用されている. DPCデータを用いて大規模多施設コホート研究を行い, AT単独に比べATとTMの併用療法が退院時転帰に影響するかを検討した. AT群は352病院1,017症例、AT+TM群は349病院1,205症例であった. AT+TMはATに対する院内死亡率のオッズ比が0.98 (P=0.84) であり, 統計学的な有意差はみられなかった. アンチトロンビン製剤単独投与と比べ併用療法が死亡率を改善するという結果は示されなかった.

Antithrombin (AT) and thrombomodulin (TM) combination anticoagulant therapy is frequently used to treat septic patients with DIC in Japan. In this large-scale multicentre retrospective study of adult septic patients with DIC, we compared in-hospital mortality between AT monotherapy and AT+TM combination therapy. The AT group and AT+TM group comprised 1,017 patients from 352 hospitals and 1,205 patients from 349 hospitals, respectively. AT+TM combination therapy was not significantly associated with lower mortality (odds ratio: 0.98; P=0.84). AT+TM combination therapy is not more effective in improving prognoses than the simpler AT monotherapy.

Muguruma K, Kunisawa S, Fushimi K, Imanaka Y. The epidemiology and volume-outcome relationship of extracorporeal membrane oxygenation for respiratory failure in Japan: A retrospective observational study using a national administrative database. Acute Medicine & Surgery 2020 ; 7: e486 ; PMID: 32076555 ; DOI: 10.1002/ams2.486


Using data from the Diagnosis Procedure Combination database between 1 July 2010 and 31 March 2018, the present study aimed to investigate the possible association between outcomes for respiratory ECMO patients and hospital volume of ECMO treatment for any indications in Japan. The result showed that accumulating the experience of ECMO for any indications could positively affect the outcome of ECMO treatment for respiratory failure, which suggests the effectiveness of consolidating ECMO cases in high-volume centers in Japan.

Morii D, Tomono K, Imanaka Y. Economic impact of antimicrobial-resistant bacteria outbreaks on Japanese hospitals. American Journal of Infection Control 2020 Oct;48(10):1195-1199 ; PMID: 31955855 ; DOI: 10.1016/j.ajic.2019.12.006

Sasaki N, Groenewoud S, Kunisawa S, Westert G, Imanaka Y. Public needs for information disclosure on healthcare performance: Different determinants between Japan and the Netherlands. Medicine 2019 ;98:43(e17690) ; PMID: 31651898 ; DOI: 10.1097/MD.0000000000017690


Regarding citizens’ preference and value towards public disclosure and healthcare equity, analyses based on the online survey revealed sharp contrasts between the two countries. Japanese showed relatively lower interest in knowing information and seemed to accept inequality, while the Dutch mostly showed high interest. Female/older respondents tended to show high interest in obtaining information across countries. Health service stakeholders should recognize the varying willingness and competency to use complex information among subgroups, in order to empower the public.

Lin H, Imanaka Y. Effects of copayment in long-term care insurance on long-term care and medical care expenditure. JAMDA 2019 ; PMID: 31623988 ; DOI: 10.1016/j.jamda.2019.08.021

日本における2015年8月に年間収入が一定金額以上の介護被保険者にサービス利用際の自己負担を1割から2割に上昇した政策に及ぼす介護・医療サービス利用と費用の影響を、差分の差分法で分析した。介護自己負担割合を上昇に、医療と介護のballon effectが見られることにより、介護政策を策定する際に、医療制度と合わせて検討する必要があると考えられる。

We used the database to include 570,434 person-month records of 23,879 insured individuals. Conducted difference-in-difference estimations to clarify the difference in long-term care and medical care usage and expenditure before and after the change in the copayment limit for qualifying individuals from 10% to 20% in August 2015 in Japan. The increase in insured individuals' copayment would appear to be a "balloon effect" between long-term care and medical service.

Bun S, Kunisawa S, Sasaki N, Fushimi K, Matsumoto K, Yamatani A, Imanaka Y. Analysis of concordance with antiemetic guidelines in pediatric, adolescent, and young adult patients with cancer using a large‐scale administrative database. Cancer Medicine 2019 ;8:6243–6249 ; PMID: 31469518 ; DOI: 10.1002/cam4.2486

本研究は、小児および思春期・若年成人(AYA)世代がん患者における抗がん剤の投与時の予防的制吐剤のガイドライン適合率を調査した。ガイドラインの一致率は、成人で報告されているガイドライン一致率である70%-90%と比較し低いものであった。(最小度催吐性リスク51.6%、軽度催吐性リスク5.9%、中等度催吐性リスク32.1%、18歳以上の高度催吐性リスク51.1%、18歳未満のHEC 18.2%)。ガイドライン不一致となる因子は、低年齢児、中等度もしくは高度催吐性リスクの抗がん剤の使用、血液疾患および脳腫瘍が抽出された。またステロイドの使用は催吐リスク分類に関わらず避ける傾向が示された。小児およびAYA世代では制吐剤の使用に関して改善する余地がある可能性が示された。

This study is the rate of concordance with antiemetic guidelines for CINV in the field of pediatric, adolescent, and young adult. The concordance with the antiemetic guidelines in the pediatric population (MinEC 51.6%、LEC 5.9%、MEC 32.1%、HEC ≥ 18yr 51.1%、HEC < 18yr 18.2%) was lower than that in the adults (70-90%). The factors for discordance were younger age, use of moderate and high emetic risk chemotherapeutic drugs, hematological malignancy, and brain tumor. There is substantial scope to improve the antiemetic practice and reduce the risk of discordance with the antiemetic guidelines in pediatric, adolescent, and young adult patients.

Tsutsumi I, Kunisawa S, Yoshida C, Seki M, Komeno T, Fushimi K, Morita S, Imanaka Y. Impact of oral voriconazole during chemotherapy for acute myeloid leukemia and myelodysplastic syndrome: a Japanese nationwide retrospective cohort study. Int J Clin Oncol 2019 24, pages1449–1458 ; PMID: 31300904 ; DOI: 10.1007/s10147-019-01506-x

本研究は成人急性骨髄性白血病または骨髄異形成症候群の患者における、化学療法開始後7日以内の経口第一世代アゾール薬処方に対する経口ボリコナゾール処方の有用性をDPCデータを用いて調べた研究である。経口第一世代アゾール薬と比較し、経口ボリコナゾール処方は点滴抗真菌薬使用割合を有意に減少させた(−21.0%, 95%信頼区間 − 33.4 to − 8.6)。65歳未満の患者、および化学療法開始3日以内に処方を開始された患者で特に影響が大きかった。経口ボリコナゾール処方は成人急性骨髄性白血病または骨髄異形成症候群の化学療法中の患者に有用である。

This study aimed to investigate the effectiveness of oral voriconazole (VRCZ) relative to that of first-generation azoles prescribed within 7 days after the onset of chemotherapy among adult patients with acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) under chemotherapy using the Diagnosis Procedure Combination/Per-Diem Payment System. The result shows that an oral VRCZ prescription was significantly associated with a reduction in the proportion of patients switching to intravenous antifungal agents compared to first-generation azole prescription by 21.0% (95% confidence interval [CI] − 33.4 to − 8.6). The impact of oral VRCZ in reducing the proportion of patients switching to intravenous antifungal agents was stronger in patients aged < 65 years and in patients prescribed oral azole within 3 days from the onset of chemotherapy. Oral VRCZ administration may benefit adult patients with AML/MDS undergoing chemotherapy.

Nakabe T, Sasaki N, Uematsu H, Kunisawa S, Wimo A, Imanaka Y. Classification tree model of the personal economic burden of dementia care by related factors of both people with dementia and caregivers in Japan: a cross-sectionalonline survey. BMJ Open 2019 8:e026733 ; PMID: 31289069 ; DOI: 10.1136/bmjopen-2018-026733

本研究では、認知症の人とその介護者に関連する要因によりサブグループに分類することにより、在宅での認知症介護の経済負担のミクロレベルの決定要因を明らかにした。 認知症介護における資源利用の状況を把握するため、Resource Utilization in Dementia (RUD)を用いたインターネット質問紙調査を実施した。 家族らにより無償提供されるインフォーマルケアのコストは、介護休業者で最も高く、介護者の有職状況や同居状況が、認知症の人の要因よりも関連した。 一方で、介護サービスへの自己負担額は主に認知症の人の要介護度や家族の経済状況が主に関連して分類された。 個人単位での認知症介護の経済負担を分類した本研究結果は、どのような状況下で大きな経済負担を表すか理解するのに役立ち、 日本における認知症ケアシステムの持続可能性を改善するように有用となりうる。

This study aimed to clarify the micro-level determinants of the economic burden of dementia care at home in Japanese community settings by classifying them into subgroups of factors related to people with dementia and their caregivers. We conducted an online questionnaire survey which use the Resource Utilization in Dementia (RUD) to collect the data about resource use in persons with dementia and their caregivers. Informal care costs were related to caregivers’ employment and cohabitation status rather to the situations of people with dementia. On the other hand, out-of-pocket payments for LTC services were related to care-need levels and family economic status. These classifications will be useful in understanding which situation represents a greater economic burden and helpful in improving the sustainability of the dementia care system in Japan.

Sasaki N, Yamaguchi N, Okumura A, Yoshida M, Sugawara H, Imanaka Y. Does Hospital Information Technology Infrastructure Promote the Implementation of Clinical Practice Guidelines? A Multicenter Observational Study of Japanese Hospitals. BMJ Open 2019 9:e024700 ; PMID: 31203235 ; DOI: 10.1136/bmjopen-2018-024700


Wide variations were observed in the availability of various IT infrastructure elements across hospitals, especially in local area network availability and access to paid evidence databases. Hospitals with superior IT infrastructure may provide higher-quality care. This allows clinicians to easily access the latest information on evidence-based medicine and facilitate the dissemination of CPGs.

Shin J, Kunisawa S, Fushimi K, Imanaka Y. Effects of preoperative oral management by dentists on postoperative outcomes following esophagectomy: Multilevel propensity score matching and weighting analyses using the Japanese inpatient database. Medicine 2019 Apr;98(17):e15376 ; PMID: 31027127 ; DOI: 10.1097/MD.0000000000015376

歯科医師による術前口腔管理が食道切除術後のアウトカムに及ぼす影響を調べるため、DPC調査研究班のデータベースより退院日が2016年4月から2017年3月までの開胸および胸腔鏡下食道切除術症例を抽出し、マルチレベル傾向スコア分析を行った(n=2,600、うち開胸:956例、胸腔鏡下手術:1,644例)であった。2つのモデルにより算出した傾向スコアによるIPTW(inverse probability of treatment weighting)解析の結果、術後誤嚥性肺炎の発症割合が開胸食道切除術後は口腔管理群で1.5~1.6%、非管理群で4.0~4.1%(risk difference、RD:–2.5~–2.5%)、胸腔鏡下食道切除術後は口腔管理群で2.4~2.6%、非管理群で4.5~4.6%(RD:–2.1~–2.0%)であり、口腔管理群における発症の有意な減少を認めた。また、口腔管理群の胸腔鏡下食道切除術の医療費が非管理群より有意に削減した(口腔管理群:3,412,071~3,448,760円、非管理群:3,665,198~3,670,003円、差:–253,127~–221,243円)。本結果から、術後合併症のリスクが高いと判断される患者のみではなく、全患者を対象とした通常の周術期管理として術前口腔管理の実施を考慮する必要がある。

To investigate the effects of preoperative oral management (POM) by dentists on outcomes following both open and thoracoscopic esophagectomy, we extracted data of esophagectomy cases from the Japanese Diagnosis Procedure Combination database, of which discharge dates were between April 2016 and March 2017 (n=2,600; open: 956, thoracoscopic surgery: 1,644 cases). We subsequently conducted propensity score (PS) analyses for multilevel data. IPTW (inverse probability of treatment weighting) analysis using PSs derived by two multilevel models to estimate the average treatment effect, the risk difference of postoperative aspiration pneumonia ranged from –2.49% to –2.02% between the POM and control groups of both open and thoracoscopic esophagectomy cases. IPTW analyses also indicated that the total medical costs of thoracoscopic esophagectomy were reduced by 221,200 to 253,100 Japanese Yen (equivalent to about $2,000 to $2,200). Our results suggested that POM by dentists can be considered as a routine perioperative care for all patients undergoing esophagectomy, regardless of the expected risk for PPC.

Hara K, Nakabe T, Naka T, Tanaka M, Imanaka Y. Visualizing organizational culture in old people’s homes and hospitals in Japan: Human interaction in the IoT era. Human Aspects of IT for the Aged Population. Social Media, Games and Assistive Environments. HCII 2019. Lecture Notes in Computer Science 11593 2019 June ; DOI: 10.1007/978-3-030-22015-0_25

Tanke MAC, Feyman Y, Bernal-Delgado E, Deeny SR, Imanaka Y, Jeurissen P, Lange L, Pimperl A, Sasaki N, Schull M, Wammes J, Wodchis WP, Meyer GS. A challenge to all. A primer on inter-country differences of high-need, high-cost patients. Plos One 2019 Jun 19;14(6):e0217353 ; PMID: 31216286 ; DOI: 10.1371/journal.pone.0217353

先進 7 カ国(カナダ、英、米、独、日本、オランダ、スペイン)の年間医療費高額患者(上位 5%・1%)集団の特徴、医療費、コスト集中度、医療資源利用の違い等の詳細について、医療管理データ(個票レベル)を用いて示した。総医療費上位5%者の年間総医療費寄与割合は41%(日本)~60%(カナダ)とばらつき、平均入院日数もばらつく等、医療制度の違いも比較検討の際に考慮する必要があると考えられた。

To better understand the characteristics and healthcare utilization of high-cost populations in different health system, we conducted a cross-sectional descriptive study using patient-level data on high-cost patients in seven high-income OECD member countries. Cost-concentration of the top 5% of patients varied across countries, from 41% in Japan to 60% in Canada. Differences in the way that health systems are structured likely explains some of this variation.

Hamada O, Tsutsumi T, Miki A, Fukui T, Shimokawa T, Imanaka Y. Impact of the Hospitalist System in Japan on the Quality of Care and Healthcare Economics. Internal Medicine 2019 58(23):3385-3391 ; PMID: 31391388 ; DOI: 10.2169/internalmedicine.2872-19

Takada D, Kunisawa S, Fushimi K, Imanaka Y. Previously-initiated hemodialysis as prognostic factor for in-hospital mortality in pneumonia patients with stage 5 chronic kidney disease: Retrospective database study of Japanese hospitals. Plos One 2019 Feb 28;14(2):e0213105 ; PMID: 30818331 ; DOI: 10.1371/journal.pone.0213105


Japanese hemodialysis patients have a good prognosis, but mortality due to myocardial infarction or infective patients are regarded as critical problems, but there are few large-scale papers comparing with patients who had not been introduced hemodialysis. We analyzed in-hospital death of pneumonia hospitalized patients of CKD 5 (D) patient with various variables using multivariate logistic regression, propensity score analysis, multilevel analysis, multiple imputation method. All the analysis revealed previous introduced hemodialysis have a significant good prognosis. Although RCTs abroad indicated no difference, however, we should be careful when we introduce hemodialysis in Japan.

Aoyama T, Kunisawa S, Fushimi K, Sawa T, Imanaka Y. Comparison of surgical and conservative treatment outcomes for type A aortic dissection in elderly patients. Journal of Cardiothoracic Surgery 2018 13(1):129 ; PMID: 30563552 ; DOI: 10.1186/s13019-018-0814-6


Whether emergency surgical intervention should be performed in elderly patients with type A acute aortic dissection (AAD) is controversial because of the high postoperative mortality and complication rates Therefore, this study compares the conservative and surgical management of patients with AAD aged > 80 years after adjusting for severity by propensity scores using data from the national inpatient database in Japan. All-cause in-hospital death was significantly lower in the surgical treatment group than in the conservative treatment group after matching, complications were more frequent in the surgical group, but there was no difference in ADL at discharge. Therefore AAD surgery is effective even in the elderly patients.

Iwashita Y, Yamashita K, Ikai H, Sanui M, Imai H, Imanaka Y, JSEPTIC. Epidemiology of mechanically ventilated patients treated in ICU and non-ICU settings in Japan: a retrospective database study. Critical Care 2018 22(1):329 ; PMID: 30514327 ; DOI: 10.1186/s13054-018-2250-3

Umegaki T, Kunisawa S, Kotsuka M, Yamaki S, Kamibayashi T, Imanaka Y. The impact of low body mass index on postoperative outcomes in pancreatectomy patients: a retrospective analysis of Japanese administrative data. Journal of Anesthesia 2018 32(4):624-631 ; PMID: 29936599 ; DOI: 10.1007/s00540-018-2527-3

膵臓癌手術ではBMI低値症例の予後不良の報告はみられるが, underweight症例の中でWHO分類に沿ったカテゴリーごとの死亡リスクは検討されていない. 膵臓癌手術を受けた6,173症例において, BMIが低値症例(Mild thinness(BMI: 17.00-18.49), Moderate thinness(BMI: 16.00-16.99), Severe thinness(BMI: <16.00))の院内死亡率を標準的なBMI(Normal(BMI: 18.50-24.99))症例を対象に比較検討を行った. 多変量解析の結果, Normal BMIに対してSevere thinnessはオッズ比が2.54(95%信頼区間:1.05-6.08)(p=0.04)であった. 膵臓癌における手術においてSevere thinnessの症例はNormal BMIに対して院内死亡率が統計学的に有意に高くなることが示唆された.

To comparatively examine in-hospital mortality among different underweight body mass index (BMI) categories in pancreatic cancer patients after pancreatectomy.
We conducted a large-scale multi-center retrospective cohort study of adult patients with pancreatic cancer who underwent pancreatectomy between April 1, 2010 and March 31, 2016. Relative to the normal BMI group, the odds ratios for in-hospital mortality was 2.54 (1.05–6.08; P = 0.04) in the severe thinness group. In conclusion, severe thinness was significantly associated with a higher risk of mortality, and extremely low BMI should be considered a risk factor in pancreatectomy patients.

Hara K, Kunisawa S, Sasaki N,, Imanaka Y. Future Projection of the Physician Workforce and Its Geographic Equity in Japan: A Cohort-Component Model. BMJ Open 2018 8:e023696 ; PMID: 30224401 ; DOI: 10.1136/bmjopen-2018-023696

医師数地域格差の将来推計を、コホート要因モデルを用いて行った。 都市/地方×医療資源多/寡で二次医療圏を4グループに分けたが、全てで人口対医師数は増加するものの、地域格差自体は拡大し続けることが明らかになった。 また、地方で医師が少ない地域グループでは、医師の高齢化が特に早く進むことが示された。

We projected the geographic distribution of physicians in Japan in the future by a cohort-component model.we divided 342 areas into 4 area groups based on urban/rural status and lower/higher physician supply, based on earlier studies.As the result, the inequity in the geographical distribution of physicians will expand despite an increase in the number of physicians in rural areas.In addition, the proportion of aged physicians will increase in all areas, especially in rural ones with an initially lower supply, where it will change from 14.4% in 2005 to 31.3% in 2035.

Mizuno S, Iwami M, Kunisawa S, Naylor N, Yamashita K, Kyratsis Y, Meads G, Otter JA, Holmes A, Imanaka Y, Ahmad R. Comparison of national strategies to reduce methicillin-resistant Staphylococcus aureus (MRSA) infections in Japan and England. The Journal of Hospital Infection 2018 100(3):280-298 ; PMID: 30369423 ; DOI: 10.1016/j.jhin.2018.06.026


National responses to healthcare-associated infections vary between high-income countries but when analysed for contextual comparability, interventions can be assessed for transferability. This study addressed the question: What can be learnt from approaches for addressing MRSA between two high-income countries? In England significant reduction has been achieved in number of reported MRSA bloodstream infections. In Japan, in spite of reductions, MRSA remains a predominant infection. Both countries face new threats in the emergence of drug-resistant Escherichia coli. England has focused on national mandatory and structural interventions, supported by a combination of outcomes-based incentives and punitive mechanisms, and multidisciplinary IPC hospital teams. Japan has focused on (non-mandatory) recommendations and primarily persuasive interventions, supported by process-based incentives, with voluntary surveillance. Policy interventions need to be relevant to local epidemiological trends, while acceptable within health system cultures and public expectations. Cross-national learning can help inform the right mix of interventions to create sustainable and resilient systems for future infection and economic challenges.

Sasaki I, Kondo K, Kondo N, Aida J, Ichikawa H, Kusumi T, Sueishi N, Imanaka Y. Are pension types associated with happiness in Japanese older people?: JAGES Cross-sectional study. Plos One 2018 ; PMID: 29782505 ; DOI: 10.1371/journal.pone.0197423

Hirose M, Nishimura N, Kawamura T, Kumakura S, Telloyan J, Igawa M, Fukuda H, Imanaka Y. Do pharmacists have the most potential for patient safety in Japan? Learning from a 2010 nationwide survey. Journal of Hospital Administration 2018 7(3)40-48 ; DOI: 10.5430/jha.v7n3p40


Uematsu H, Yamashita K, Mizuno S, Kunisawa S, Shibayama K, Imanaka Y. Effect of Methicillin-Resistant Staphylococcus aureus in Japan. American Journal of Infection Control 2018 112:88-96 ; PMID: 29784441 ; DOI: 10.1016/j.ajic.2018.04.214

本研究では、日本の病院におけるメチシリン耐性黄色ブドウ球菌(MRSA)に起因する臨床的および経済的負担を分析した。DPCデータおよび厚生労働省院感染対策サーベイランス(JANIS)データを突合し、2014年4月から2年の間で入院した57病院・14,905人を調査対象とした。アウトカムとして在院日数・入院費用・院内死亡率とし、MRSA感染患者群とメチシリン感受性黄色ブドウ球菌(MSSA)感染患者群を患者重症度と在院中発症日も調整して比較した。 7,188人と7,717人の患者をそれぞれMRSA群とMSSA群に分類した。調整なしでのMRSA群の疾病負荷に対する効果はそれぞれ1.15倍(95%信頼区間[CI] 1.12-1.19)、1.16倍(95%CI 1.13-1.19)および1.46(オッズ比)(95%CI 1.31-1.61)であった。MRSA群の調整済み効果は1.03倍(95%CI 1.01-1.05)、1.04倍(95%CI 1.01-1.06)および1.14(オッズ比)(95%CI 1.02-1.27)であり、メチシリン耐性の疾病負荷は患者重症度や入院後発症日を調整後も有意に存在することを確認した。また、患者の重症度が重いほど、在院中の黄色ブドウ球菌感染症発症日が遅いほど、MRSAである確率が高く、臨床的・経済的負担は重いことを見出した。

This study analyzed the clinical and economic burdens attributable to methicillin resistance in Staphylococcus aureus(MRSA) in Japanese hospitals. We retrospectively investigated data from 14,905 inpatients of 57 hospitals combined with data from nosocomial infection surveillance and administrative claim databases. The outcomes were evaluated according to the length of stay, hospital charges, and in-hospital mortality. We compared the burden of diseases with MRSA to those with methicillin-susceptible Staphylococcus aureus (MSSA) infections based on patients' characteristics and onset periods. We categorized 7,188 and 7,717 patients into MRSA and MSSA groups, respectively. The crude effects of the MRSA group were 1.15 fold (95% confidence interval [CI] 1.12-1.19), 1.16-fold (95% CI 1.13-1.19), and 1.46 (odds ratio) (95% CI 1.31-1.61), respectively. The adjusted effects of the MRSA group were 1.03-fold (95% confidence interval [CI] 1.01-1.05), 1.04-fold (95% CI 1.01-1.06), and 1.14 (odds ratio) (95% CI 1.02-1.27), respectively. The results of the present study found that patient severity and onset delays were positively associated with both MRSA and burden and that the effect of methicillin resistance remained significant after adjustment.

Lertjanyakun V, Chaiyakunapruk N, Kunisawa S, Imanaka Y. Cost-effectiveness of Second-Line Endocrine Therapies in Postmenopausal Women with Hormone Receptor–positive and Human Epidermal Growth Factor Receptor 2–negative Metastatic Breast Cancer in Japan. PharmacoEconomics 2018 36(9), 1113-1124 ; PMID: 29707743 ; DOI: 10.1007/s40273-018-0660-3

ホルモン受容体(HR)陽性HER2陰性の転移性乳癌に対する2次治療としての各種ホルモン療法について、確率的感度分析を伴う費用対効果分析を行った。exemestane (EXE)、exemestane + everolimus (EXE + EVE)、toremifene (TOR)、fulvestrant (FUL)を対象とした。EXEに比しTOR、FUL(250mg)の増分費用対効果比はそれぞれ約300万円/ QALY、約600万円/ QALYと推計された。他ではかなり高値であった。またこれらの結果は全生存率(overall survival)のハザード比に大きく影響を受けることが明らかとなった。

Nakabe T, Sasaki N, Uematsu H, Kunisawa S, Wimo A, Imanaka Y. The personal cost of dementia care in Japan: a comparative analysis of residence types. International Journal of Geriatric Psychiatry 2018 33(9), 1243-1252; ; PMID: 29892984 ; DOI: 10.1002/gps.4916

本研究では、日本の認知症介護における個人の経済負担の状況について、居住形態別に把握した。 認知症介護における資源利用の状況を把握には、世界的にも使用されるResource Utilization in Dementia (RUD)を用いて、インターネット質問紙調査を実施した。経済負担を構成する各費用(インフォーマルケアコスト、介護保険サービス自己負担額、介護保険外サービス自己負担額、医療費自己負担額)を、認知症の人の年齢・性別・要介護度で調整したOE比を用いて居住形態別に比較した。 在宅介護ではインフォーマルケアコストは施設入居の場合と比較してはるかに高く、自己負担額は低くても、経済負担が高かった。有料老人ホームやサービス付き高齢者向け住宅の場合は、介護保険外サービスの自己負担額が高かった。本研究の結果は、持続可能な認知症ケアシステムを構築するための政府の財政負担と介護者の経済的負担とのバランスを考慮の一助となりうる。

This study aimed to quantify the personal economic burden of dementia care in Japan according to residence type. We conducted an online questionnaire survey which use the Resource Utilization in Dementia (RUD) to collect the data about resource use in persons with dementia and their caregivers. To compare dementia care costs among residence types, we calculated the ratio between the observed and expected values (OE ratio) for the costs of dementia care for each residence type by adjusting for the characteristics of people with dementia (care‐needs level, sex, and age categories). In a community setting, informal care costs were much higher than in institutions, and the total costs that included these informal care costs were also higher despite the lower out‐of‐pocket payments. These results support considering the balance between the government's fiscal burden and caregivers' economic burdens to construct a sustainable dementia care system.

Lin H, Tsuji T, Kondo K, Imanaka Y. Development of a Risk Score for the Prediction of Incident Dementia in Older Adults using a Frailty Index and Health Checkup Data: The JAGES Longitudinal Study. Preventive Medicine 2018 112:88-96 ; PMID: 29626553 ; DOI: 10.1016/j.ypmed.2018.04.004

介護ニーズに関する基本チェックリストと健診データのみを用いて、Cox比例ハザードモデルから、認知症発症のリスクスコアモデル(C統計量は0.733から0.790)を生成した。これにより既存のデータから認知症発症のリスクがスコア化できるようになる。認知症発症のハイリスク者の同定や認知症予防施策の推進に有用なツールに繋がると思われる。JAGES(Japan Gerontological Evaluation Study, 日本老年学的評価研究)との共同研究。

We performed Cox regression analyses to develop three risk score models for the prediction of incident dementia in older adults using a frailty index (so-called "Kihon chesklist") and health checkup data. We identified 6,656 (9.2%) individuals who developed incident dementia during the observation period. The C-statistics of the risk score models ranged from 0.733 to 0.790. By predicting incident dementia in older adults, these risk score models may help detect persons at high risk for dementia and promote preventive approaches at an early stage. This is a collaborative work with the Japan Gerontological Evaluation Study (JAGES).

Mizuno S, Kunisawa S, Sasaki N, Fushimi K, Imanaka Y. Effects of night-time and weekend admissions on in-hospital mortality in acute myocardial infarction patients in Japan. Plos One 2018 13(1):e0191460 ; PMID: 29351557 ; DOI: 10.1371/journal.pone.0191460


Using multicenter DPC data, we compared and examined the in-hospital mortality of acute myocardial infarction patients. We divided patients into the following 4 groups according to the admission time: weekday daytime, weekday night-time, weekend daytime, and weekend night-time. The in-hospital mortality rate of weekend daytime admissions was higher than those admitted during other times, even after adjusting for the covariates (adjusted odds ratio admissions; 1.10; confidence interval: 1.03-1.19)

Hara K, Kunisawa S, Sasaki N, Imanaka Y. Examining changes in the equity of physician distribution in Japan: a specialty-specific longitudinal study. BMJ Open 2018 8(1):e018538 ; PMID: 29317415 ; DOI: 10.1136/bmjopen-2017-018538


We conducted longitudinally examine specialty-specific changes in the geographical distribution of physicians in Japan with adjustments for healthcare demand based on population structure. We found that there was a growing urban睦ural disparity in physician supply in internal medicine, surgery, orthopaedics, OB/GYN, and anaesthesiology.

Yoshihisa Tsuji, Naoki Takahashi, Hiroyoshi Isoda, Koji Koizumi, Sho Koyasu, Miho Sekimoto, Yuichi Imanaka, Shujiro Yazumi, Masanori Asada, Yoshihiro Nishikawa, Hiroshi Yamamoto, Osamu Kikuchi, Tsukasa Yoshida, Tetsuro Inokuma, Shinji Katsushima, Naoki Esaka, Akihiro Okano, Chiharu Kawanami, Nobuyuki Kakiuchi, Masahiro Shiokawa, Yuzo Kodama, Ichiro Moriyama, Takafumi Kajitani, Yoshikazu Kinoshita, Tsutomu Chiba. Early diagnosis of pancreatic necrosis based on perfusion CT to predict the severity of acute pancreatitis. Journal of Gastroenterology 2017 52(10):1130-1139. ; PMID: 28374057 ; DOI: 10.1007/s00535-017-1330-5

Umegaki T, Kunisawa S, Nakajima Y, Kamibayashi T, Fushimi K, Imanaka Y. A comparison of in-hospital outcomes between transcatheter and surgical aortic valve replacement in patients with aortic valve stenosis: a retrospective cohort study using administrative data. Journal of Cardiothoracic and Vascular Anesthesia 2017 32(3):1281-1288 ; PMID: 29422279 ; DOI: 10.1053/j.jvca.2017.06.047


his study aimed to compare in-hospital outcomes between TAVI and SAVR using a multi-center administrative database in Japan. TAVI produced better clinical outcomes in patients with aortic valve stenosis. The improved outcomes were particularly notable in patients aged 80 years or older.

Hirose M, Kawamura T, Igawa M, Imanaka Y. Patient safety activity under the social insurance medical fee schedule in Japan: An overview of the 2010 nationwide survey. Journal of Patient Safety 2017 ; PMID: 29189440 ; DOI: 10.1097/PTS.0000000000000432


Patient safety activities at hospitals in large-scale hospitals were performed more quickly than those in small-scale hospitals. However, when the values were converted to per 100 beds, there were no differences across the three groups. Therefore, Hospitals in group C actually showed the same or greater activity levels than those in groups A and B. PPSCF encouraged hospitals to perform actions for patient safety by providing incentives under the social insurance medical fee schedule in Japan.

Okumura K, Hida K, Kunisawa S, Nishigori T, Hosogi H, Sakai Y, Imanaka Y. Impact of drain insertion after perforated peptic ulcer repair in a Japanese nationwide database analysis. World Journal of Surgery 2017 42(3):758-765 ; PMID: 28920145 ; DOI: 10.1007/s00268-017-4211-4


This study aimed to investigate the drain insertion rates in patients who underwent perforated peptic ulcer(PPU) repair in Japan, and to clarify the impact of drain insertion on the postoperative clinical course by using Japanese DPC database. Postoperative drainage was performed in more than ninety per cent of the patients who underwent PPU repair in Japan. Drainage following PPU repair may facilitate patient recovery by reducing the need for postoperative interventions.

Lin H, Otsubo T, Imanaka Y. Survival analysis of increases in care needs associated with dementia and living alone among older long-term care service users in Japan. BMC Geriatrics 2017 17(1):182. ; PMID: 28814271 ; DOI: 10.1186/s12877-017-0555-8

本研究は京都府の介護保険‎、後期高齢者医療制度、国民健康保険データベースを用いて、2010年10月から2011年9月まで介護サービス利用があった、65歳以上、要介護度5未満の介護サービス利用者を対象とし、2015年3月まで追跡した。Cox Regressionで要介護度悪化予測モデルを構築する。低い要介護度、認知症がある、高齢、女性は要介護度悪化と関連があった。認知症は要介護度悪化にもっとも影響がある要因であり、特に認知症をもつ独居の場合はより影響が大きく見られた。

We used the Long-term care insurance claims data to identify enrollees who applied for long-term care services between October 2010 and September 2011, and subjects were tracked until March 2015 to examine the influence of dementia and living alone on care needs increases among older long-term care insurance service users in Japan. Dementia, older age, the female sex, and lower care needs levels were associated with a higher risk of care needs increases over the study period, and dementia showed the strongest impact on care needs increases, especially in person who lived alone.

Uematsu H, Yamashita K, Kunisawa S, Otsubo T, Imanaka Y. Prediction of pneumonia hospitalization in adults using health checkup data. Plos One 2017 Jun 29;12(6):e0180159 ; PMID: 28662167 ; DOI: 10.1371/journal.pone.0180159


This study aimed to develop a predictive model for pneumonia hospitalization in adults to accurately identify high-risk individuals, using health checkup data and health insurance claims data for residents of Kyoto prefecture. Our prediction model for pneumonia hospitalization performed better than age & comorbidities’ models, and may be useful for supporting the development of pneumonia prevention measures.

Uematsu H, Yamashita K, Kunisawa S, Fushimi K, Imanaka Y. Estimating the disease burden of methicillin-resistant Staphylococcus aureus in Japan: retrospective database study of Japanese hospitals Plos One 2017 Jun 27;12(6):e0179767 ; PMID: 28654675 ; DOI: 10.1371/journal.pone.0179767


This study aimed to estimate the disease burden of methicillin-resistant Staphylococcus aureus infections in Japanese hospitals using Japanese DPC database. The mean hospitalization costs, length of stay, and in-hospital mortality of the anti-MRSA drug group were 3.43, 2.95, and 3.66 times that of the control group, respectively. When extrapolated to the 1584 hospitals, the total incremental burden of MRSA was estimated to be US$2 billion, 4.34 million days, and 14.3 thousand deaths.

Sasaki N, Kunisawa S, Ikai H, Imanaka Y. Differences between determinants of in-hospital mortality and hospitalization costs in patients with acute heart failure: a nationwide observational study from Japan. BMJ Open 2017 Mar 22;7(3):e013753 ; PMID: 28336741 ; DOI: 10.1136/bmjopen-2016-013753


The study provides a novel understanding that determinants of in-hospital mortality and hospitalization costs differ in acute heart failure in Japan. Our findings indicate that the same case-mix classifications should not be used to predict both inpatient mortality and costs, which would support the development and implementation of future case-mix classifications.

Nori N, Kashima H, Yamashita K, Kunisawa S, Imanaka Y. Learning Implicit Tasks for Patient-Specific Risk Modeling in ICU. Proceedings of the 31st AAAI Conference on Artificial Intelligence (AAAI), 2017 1481-1487


Using DPC database, we executed predictions of ICU inpatients mortarity. Predictions are based on patients diseases. Our method achieved higher predictive performance compared with a single-task learning method, the “de facto standard,” and several multi-task learning methods including a recently proposed method for ICU mortality risk prediction. Furthermore, our method uncovers patient-specificity from different viewpoints.

Hara K, Otsubo T, Kunisawa S, Imanaka Y. Examining sufficiency and equity in the geographic distribution of physicians in Japan: a longitudinal study. BMJ Open 2017 Mar 14;7(3):e013922 ; PMID: 28292766 ; DOI: 10.1136/bmjopen-2016-013922


This study longitudinally examines the geographic distribution of physicians in Japan by adjusting healthcare demand according to the changing age structure of the population. The number of physicians per 100,000 raw population had seemingly increased in urban and rural areas in Japan. After healthcare demand was adjusted, however, physician supply was observed to decrease even in urban areas with a high initial supply. In addition, physician distribution had consistently become less equitable across the regions since 2000.

Kunisawa S, Fushimi K, Imanaka Y. Reducing length of hospital stay does not increase readmission rates in early-stage gastric, colon, and lung cancer surgical cases in Japanese acute care hospitals. Plos One 2016 Nov 10;11(11):e0166269 ; PMID: 27832182 ; DOI: 10.1371/journal.pone.0166269


Using DPC data, we analyzed early-stage gastric, colon, and lung cancer surgical patients in Japan. Length of stay reduced but readmission rates did not increased.

Hanaki N, Yamashita K, Kunisawa S, Imanaka Y. The effect of the number of request calls on the time from call to hospital arrival: a cross-sectional study of an ambulance record database in Nara prefecture, Japan. BMJ Open [Internet] 2016 Dec 9 [cited 2016 Dec 14];6(12):e012194. ; PMID: 27940625 ; DOI: 10.1136/bmjopen-2016-012194


We conducted a cross-sectional study using an ambulance records database from Nara prefecture, Japan. A higher number of request calls was associated with longer time intervals to hospital arrival (addition of 6.3 min per request call). In an analysis dividing areas into three groups, there were differences in transportation time for diseases needing cardiologists, neurologists, neurosurgeons and orthopaedists.

Mizuno S, Kunisawa S, Sasaki N, Fushimi K, Imanaka Y. In-hospital mortality and treatment patterns in acute myocardial infarction patients admitted during national cardiology meeting dates. International Journal of Cardiology 2016 220:929・36 ; PMID: 27420345 ; DOI: 10.1016/j.ijcard.2016.06.168


Using multicenter DPC data, we compared and examined the in-hospital death and treatment contents of acute myocardial infarction patients admitted at the time of the cardiovascular academic conference meeting and acute myocardial infarction patients hospitalized at other times. There was no significant difference in death during hospitalization, and univariate / multivariate logistic regression analysis showed no significant association between hospital stay and hospital death. Comparison of outcomes using alternate control groups, admission on the meeting days was significantly associated with lower in-hospital mortality of AMI patients after adjustment for the covariates in case of 3 and 4 weeks.

Sugiura S, Ito T, Koyama N, Sasaki N, Ikai H, Imanaka Y. Asymptomatic C-reactive protein elevation in neutropenic children. Pediatrics International 2016 0,1 ; PMID: 27362735 ; DOI: 10.1111/ped.13077


The values of CRP (high sensitivity measurement) are usually undetectable in the patients with acute leukemia who are undergoing chemotherapies. We retrospectively investigated the episodes when the values of CRP were elevated slightly in such patients, and showed that the probability of development of FN is higher in such conditions and prophylactic administration of broad-spectrum antibiotics may prevent it effectively.

Uematsu H, Yamashita K, Kunisawa S, Fushimi K, Imanaka Y. The economic burden of Methicillin-resistant Staphylococcus aureus in community-onset pneumonia inpatients. American Journal of Infection Control 2016 Dec 1;44(12):1628-1633 ; PMID: 27475333 ; DOI: 10.1016/j.ajic.2016.05.008


This study aimed to estimate the burden of methicillin-resistant Staphylococcus aureus infections in adult inpatients with pneumonia using Japanese DPC database. In propensity score-matching analysis, the median length of stay, antibiotic costs, hospitalization costs and in-hospital mortality of the anti-MRSA drug group were 1.4, 3.8, 1.7 and 1.9 times those of the control group, respectively.

Hayashida K, Umegaki T, Ikai H, Murakami G, Nishimura M, Imanaka Y. The relationship between sedative drug utilization and outcomes in critically ill patients undergoing mechanical ventilation. Journal of Anesthesia 2016 Oct;30(5):763-9 ; PMID: 27312979 ; DOI: 10.1007/s00540-016-2196-z

ICUで人工呼吸器を装着している重症患者について、鎮静剤の使用パターンとそ のパターンとアウトカムとの関係を、 大規模データを用いて明らかにした日本で最初の研究である。最も一般的に使 用されていた鎮静剤は プロポフォールであり、他の薬剤に比べ良好な患者アウトカムと関連していた。

This is the first study based on a large-scale analysis in Japan to elucidate sedative drug utilization patterns and their relationship with outcomes in critically ill patients undergoing mechanical ventilation in ICUs. The most commonly used sedative was propofol, which was associated with favorable patient outcomes.

Uematsu H, Kunisawa S, Yamashita K, Fushimi K, Imanaka Y. Impact of weekend admission on in-hospital mortality in severe community-acquired pneumonia patients in Japan. Respirology 2016 905–910, July 2016 ; PMID: 27040008 ; DOI: 10.1111/resp.12788


Little is known about the consequences of weekend admission on the quality of care in patients with severe community-acquired pneumonia. We compared the risk-adjusted mortality and guideline-concordant processes of weekend versus weekdays' admission for these patients. Our findings showed that weekend admission was associated with increased mortality in patients with severe community-acquired pneumonia in Japan. This may have been influenced by lower implementation of microbiological testing.

Lin H, Otsubo T, Sasaki N, Imanaka Y. The determinants of long-term care expenditure and their interactions. International Journal of Healthcare Management 2016 ;9(4): 269-279 ; DOI: 10.1080/20479700.2016.1141469


We used descriptive statistics and multiple linear regression analysis, we investigated the associations of gender, dementia, service type, and other factors with Long-term care expenditure. Facility care service use, dementia, older age, higher care needs levels, the female gender, and women who use home care services or community-based/other care services were associated with higher Long-term care expenditure. We also found that individuals with dementia were strongly associated with increased Long-term care expenditure.

Yamada G, Imanaka Y. Input-output analysis on the economic impact of medical care in Japan. Environmental Health and Preventive Medicine 2015 20(5):379-87 (The Most Downloaded Article Award) ; PMID: 26194451 ; DOI: 10.1007/s12199-015-0478-y


Uematsu H, Kunisawa S, Kazuto Y, Imanaka Y. The Impact of Patient Profiles and Procedures on Hospitalization Costs through Length of Stay in Community-Acquired Pneumonia Patients Based on a Japanese Administrative Database PLOS ONE 2015 10(4): e0125284 ; PMID: 25923785 ; DOI: 10.1371/journal.pone.0125284


Possible factors associated with hospitalization costs were investigated using structural equation modeling with length of stay as an intermediate variable. The result indicated that patient profiles were generally shown to have greater indirect effects (through length of stay) on hospitalization costs than direct effects.

Lin H, Otsubo T,Imanaka Y. The effects of dementia and long-term care services on the deterioration of care-needs levels of the elderly in Japan. Medicine 2015 94(7):e525 ; PMID: 25700313 ; DOI: 10.1097/MD.0000000000000525


We analyzed 50,268 insurance beneficiaries aged 65 years and older who had utilized LTC services between 2010 and 2011 in Kyoto prefecture, Japan to identify predictors of care needs level deterioration and found that dementia, facility care services, the male sex, older age, and lower baseline care needs levels were associated with care needs level deterioration.

Nori N, Kashima H, Yamashita K, Ikai H, Imanaka Y. Simultaneous modeling of multiple diseases for mortality prediction in acute hospital care. Proceedings of the 21st ACM SIGKDD Conference on Knowledge Discovery and Data Mining 2015 855-864 ; DOI: 10.1145/2783258.2783308


Using DPC database, we executed predictions of ICU inpatients mortarity. Predictions are based on patients diseases. Our multi-taks learning method effectively integrates medical domain knowledge relating to the similarity among diseases and the similarity among Electronic Health Records (EHRs) into a data-driven approach by incorporating graph Laplacians into the regularization term to encode these similarities. Our results are not only consistent with existing medical domain knowledge, but also contain suggestive hypotheses that could be validated by further investigations in the medical domain.

Ukawa N, Tanaka M, Morishima T, Imanaka Y. Organizational culture affecting quality of care: guideline adherence in perioperative antibiotic use. International Journal for Quality in Health Care 2015 Feb;27(1):37-45 ; PMID: 25502553 ; DOI: 10.1093/intqhc/mzu091


We demonstrated that hospitals with a high score in organizational culture were more likely to adhere to the Japanese and CDC guidelines when compared with lower scoring hospitals, using quantitative data from a multicenter culture survey and our administrative database.

Otsubo T, Goto E, Morishima T, Ikai H, Yokota C, Minematsu K, Imanaka Y. Regional variations in in-hospital mortality, care processes, and spending in acute ischemic stroke patients in Japan. Journal of Stroke and Cerebrovascular Diseases 2015 Jan;24(1):239-51 ; PMID: 25444024 ; DOI: 10.1016/j.jstrokecerebrovasdis.2014.09.016

NDBを用いて急性期脳梗塞治療に関する二次医療圏間の地域差を明らかにした。 院内死亡率で3.2倍、tPA使用率で5.9倍の差がみられ、急性期脳梗塞治療の地域差が顕著に存在することが明らかとなった。 また、脳梗塞治療に従事する医師数が多い地域では、院内死亡率が低く、入院医療費が高かった。 加えて、医療連携が活発である地域ほど、入院医療費が低くなる傾向がみられた。

Using administrative claims data from National Claims Database (NDB), this study investigates the regional variations and associations among outcomes, care processes, spending, and physician workforce availability in acute ischemic stroke care. The regional variations among SMAs in in-hospital mortality, spending, and tPA utilization were 3.2-, 1.7-, and 5.9-fold, respectively. Higher physician supply was significantly associated with lower in-hospital mortality and higher spending. Additionally, spending had a significantly negative correlation with regional continuity of care planning rate.

Uematsu H, Kunisawa S, Sasaki N, Ikai H, Imanaka Y. Development of a risk-adjusted in-hospital mortality prediction model for community-acquired pneumonia: a retrospective analysis using a Japanese administrative database. BMC Pulmonary Medicine 2014 14:203 ; PMID: 25514976 ; DOI: 10.1186/1471-2466-14-203


We developed risk-adjusted mortality prediction models using only DPC administrative data. Our models showed high levels of discrimination for mortality prediction, with a c-statistic of 0.89 (95% confidence interval: 0.89-0.90). These models may support improvements in quality of care through inter-hospital comparisons.

Kobayashi D, Otsubo T, Imanaka Y. The effect of centralization of health care services on travel time and its equality. Health Policy 2014 Mar;119(3):298-306 ; PMID: 25480458 ; DOI: 10.1016/j.healthpol.2014.11.008


Using medical reimbursement claims data from the Kyoto branch of the Japan Health Insurance Association, we found that there are the regional variations in travel time between patient residences and medical facilities for the treatment of ischemic heart disease and breast cancer. Besides, a simulation analysis of centralization to regional core hospitals demonstrated that average patient travel times could be reduced with no detrimental effects on equality of access to care.

Sasaki N, Kunisawa S, Otsubo T, Ikai H, Fushimi K, Yasumura Y, Kimura T, Imanaka Y. The relationship between the number of cardiologists and clinical practice patterns in acute heart failure ― A cross-sectional observational study. BMJ Open 2014 Dec 30;4(12):e005988 ; PMID: 25550294 ; DOI: 10.1136/bmjopen-2014-005988

全国546 急性期病院における急性心不全38,668 症例を解析対象とした。本研究では、より望ましいとされる各種診療プロセス実施と病院あたり循環器専門医数の多さに関連があることが示された。また、リスク調整院内死亡率と専門医数とが負の関係を認めたことともあわせ、急性心不全の診療の質と人的資源に関連があることが示唆された。

We found that greater use of recommended therapeutic processes of care in acute heart failure, measured by sex-age-adjusted odds ratios, was associated with a higher number of cardiologists, using a large administrative database. Even after adjusting for disease severity factors, patients admitted to hospitals with fewer cardiologists had a higher likelihood of in-hospital mortality.

Fukuda H, Okuma K, Imanaka Y. Can experience improve hospital management? PLOS ONE 2014 Sep 24;9(9):e106884 ; PMID: 25250813 ; DOI: 10.1371/journal.pone.0106884

Ukawa N, Ikai H, Imanaka Y. Trends in hospital performance in acute myocardial infarction care: a retrospective longitudinal study in Japan. International Journal for Quality in Health Care 2014 Oct;26(5):516-523 ; PMID: 25107593 ; DOI: 10.1093/intqhc/mzu073

Goto E, Lee J, Sasaki N, Imanaka Y. Factors affecting regional variations in hospitalization expenditures of elderly residents in Japan. Journal of Public Health 2014 Volume 22, Issue 4, pp 361-370 ; DOI: 10.1007/s10389-014-0621-z


Our findings emphasize the importance of taking the level of urbanization into account when analyzing regional variations in hospitalization expenditures. Policies designed to contain healthcare expenditures should take into account these regional characteristics in order to better implement regionspecific improvements that ensure affordable healthcare in arapidly aging society.

Kunisawa S, Yamashita K, Ikai H, Otsubo T, Imanaka Y. Survival analyses of postoperative lung cancer patients: an investigation using Japanese administrative data. SpringerPlus 2014 3:217 ; PMID: 24826376 ; DOI: 10.1186/2193-1801-3-217

Stage情報を有するDPCデータを用いて、肺癌術後5年間の生存解析を行った。臨床登録データと類似の結果を呈し、また、症例の多い病院群で高い生存率がみられた。今後、広域地域のがんの治療成績のモニタリングなどに利用しうる、Administrative Databaseの潜在力を示した。我が国のAdministrative Databaseを用いれば、限界はあるものの、低コストで、迅速に、しかもデータ整備が不十分な病院群データも対象として生存率を推計できる等の利点がある。

Using an administrative database with staging information, we analyzed5-year-survival curves after the initial hospitalization due to primarynon-small cell lung cancer. The curves approximated those of the cancerregistry database. Hospitals with higher case volume showed higher 5-yearsurvival. We showed a potential of the Japanese administrative database totimely describe and monitor cancer survival rates, low in cost, of all thehospitals including those weak in data management.

Kobuse H, Morishima T, Tanaka M, Murakami G, Hirose M, Imanaka Y. Visualizing variations in organizational safety culture across an inter-hospital multifaceted workforce. Journal of Evaluation in Clinical Practice 2014 2014;20(3):273-80. ; PMID: 24661540 ; DOI: 10.1111/jep.12123

Kunisawa S, Kobayashi D, Lee J, Otsubo T, Ikai H, Yokota C, Minematsu K, Imanaka Y. Factors associated with the administration of tissue plasminogen activator for acute ischemic stroke. Journal of Stroke and Cerebrovascular Diseases 2014 23(4):724-731. ; PMID: 23910512 ; DOI: 10.1016/j.jstrokecerebrovasdis.2013.06.033

急性期脳梗塞患者の約5%にtPA投与が見られた。tPA投与には年齢や重症度が関連するが、患者宅と病院との距離には関連が見られなかった。リスク調整を行ったうえで、救急搬送が行われている場合にはtPA投与に至る割合が約4倍となり(オッズ比 4.3)、救急搬送の重要性が再認識された。

Intravenous tPA was found to be administered to approximately 5% of acute ischemic stroke patients. The administration of tPA was associated with age and stroke severities, but not with distance from patient home to hospital. After risk adjustment, ambulance use was significantly associated with tPA use (OR: 4.3), which emphasizes the need for emergency calls for an ambulance in suspected stroke patients.

Morishima T, Lee J, Otsubo T, Imanaka Y. Association of health care expenditures with aggressive versus palliative care for cancer patients at the end of life: A cross-sectional study using claims data in Japan. International Journal for Quality in Health Care 2014 26(1):79-86. ; PMID: 24225269 ; DOI: 10.1093/intqhc/mzt081


We revealed that indicators of both aggressive and palliative end-of-life care for terminally-ill cancer patients were associated with higher healthcare spending at the end of life, using health insurance claims data. These results may support the coherent development of measures to optimize aggressive care and reduce the financial burdens of terminal cancer care.

Sasaki H, Otsubo T, Imanaka Y. Widening disparity in the geographic distribution of pediatricians in Japan. Human Resources for Health 2013 Nov 22;11:59 ; PMID: 24267031 ; DOI: 10.1186/1478-4491-11-59


The trends of the pediatrician workforce were classified into four types according to the two factors: urbanization and healthcare resources. In highly urbanized and low-resource areas, the workforce increased most sharply. On the other hand, in lowly urbanized and low-resource areas, the already-old workforce were maintained in size without entry of younger or women doctors, and they were getting older. This situation alarms a dangerous state of future critical shortage in doctors in these areas.

Kunisawa S, Morishima T, Ukawa N, Ikai H, Otsubo T, Ishikawa KB, Yokota C, Minematsu K, Fushimi K, Imanaka Y. The association of geographical factors with administration of tissue plasminogen activator for acute ischemic stroke. Journal of American Heart Association 2013 Sep 17;2(5):e000336 ; PMID: 24045119 ; DOI: 10.1161/JAHA.113.000336

全国に分布する603病院の急性期脳梗塞114,194例を分析した。tPA投与率は、全体の約5%で、高齢者および重症例でより低い傾向がみられ、運転アクセス時間とは関係なかった。関連因子を調整しても、救急搬送の有無に強く関連していた(オッズ比 4)。これらの結果は、都会か地方かに係らず同様であり、脳卒中が疑われるときに迅速に救急車を呼ぶことの重要性を示唆するものであった。

We analyzed administrative claims data from 114,194 acute ischemic stroke cases admitted to 603 hospitals in Japan. Approximately 5.1% of patients received tPA. The administration of tPA was associated with patient age and severity of stroke symptoms, but driving time showed no association. Ambulance use was significantly associated with tPA administration (OR: 4.0) even after adjustment for covariates. These results are consistent across differentially urbanized regions, and suggest the importance of calling an ambulance for suspected stroke.

Park S, Sasaki N, Morishima T, Ikai H, Imanaka Y. The number of cardiologists, case volume and in-hospital mortality in acute myocardial infarction patients. International Journal of Cardiology 2013 Oct;168(4):4470-1 ; PMID: 23871346 ; DOI: 10.1016/j.ijcard.2013.06.139


Several studies have demonstrated an inverse volume-outcome relationship in AMI, but our study showed that in-hospital mortality was inversely associated with the number of cardiologists per hospital, but not with case volume. This founding suggests understanding the possible advantages of concentrating cardiologists to specific institutions in order to improve the quality of care for AMI patients.

Park S, Lee J, Ikai H, Otsubo T, Imanaka Y. Decentralization and centralization of healthcare resources: investigating the associations of hospital competition and number of cardiologists per hospital with mortality and resource utilization in Japan. Health Policy 2013 Nov;113(1-2):100-9. ; PMID: 23830562 ; DOI: 10.1016/j.healthpol.2013.06.005


Centralization of cardiologist at the hospital level and decentralization of acute hospitals at the regional level may be contributing factors for improving the quality of care in Japan. Policymakers need to strike a balance between these two approaches to improve healthcare provision and quality.

Sasaki N, Lee J, Park S, Umegaki T, Kunisawa S, Otsubo T, Ikai H, Imanaka Y. Development and Validation of an Acute Heart Failure-Specific Mortality Predictive Model Based on Administrative Data. Canadian Journal of Cardiology 2013 Sep;29(9):1055-61 ; PMID: 23395282 ; DOI: 10.1016/j.cjca.2012.11.021

85急性期病院における8620名の急性心不全患者について、DPCデータ内の年齢、性別の他、入院時の併存症、NYHA分類などを用いて、高い院内死亡予測力をもつモデルを開発した(C-statistic = 0.80)。当該モデルを用いて多くの病院で同様の定義でリスク調整予測死亡率を算出することができるようになり、評価や改善に使いうる。

We developed a new acute heart failure (AHF) mortality prediction model using an administrative database in Japan. The use of only 11 variables including older age, New York Heart Association (NYHA) functional class and severe comorbid conditions were able to accurately predict in-hospital mortality (C-statistic = 0.80). This model may facilitate risk adjustments for AHF and can contribute to further hospital evaluations.

Park S, Lee J, Ikai H, Otsubo T, Ukawa N, Imanaka Y. Quality of care and in-hospital resource use in acute myocardial infarction: Evidence from Japan. Health Policy 2013 Aug;111(3):264-72 ; PMID: 23800607 ; DOI: 10.1016/j.healthpol.2013.05.015

医療政策を立てる際、より低い医療費はより高い効率性を示しているという仮定で、単純に医療費のみに着目する考え方がある。しかし、本研究では急性心筋梗塞における医療費の高い病院グループに比べ、低い病院グループでは死亡率が高いことがわかった。 政策立案者はこの関係を理解した上で、医療政策を立てる必要がある。

At first glance, hospitals with lower resource use may appear to possess a higher level of efficiency, and policymakers may be inclined to set standards of low healthcare spending to contain costs. However, our study showed that poor quality of care in outcome measures was associated with lower resource use among AMI patients. Policymakers need to understand this inverse association before health policymaking.

Kunisawa S, Otsubo T, Lee J, Imanaka Y. Improving the assessment of prescribing: Use of a 'substitution index'. Journal of Health Services Research & Policy 2013 Jul;18(3):138-43 ; PMID: 23595576 ; DOI: 10.1177/1355819612473593


We analyzed the use of generic drugs categorized by sectors and drug types. We found not only differences in generic drug use rates, but also significant differences in maximum substitutability among sectors and clinical disciplines. We propose a fairer measure to assess the use of generic drugs in a policy context.

Yamashita K, Ikai H, Nishimura M, Fushimi K, Imanaka Y. Effect of certified training facilities for intensive care specialists on mortality in Japan. Critical Care and Resuscitation 2013 15(1):28-32. ; PMID: 23432498


Patients who were treated in ICUs certified as training facilities for intensive care specialists had better outcome than patients treated in ICU without this certification.

Umegaki T, Nishimura M, Tajimi K, Fushimi K, Ikai H, Imanaka Y. An in-hospital mortality equation for mechanically ventilated patients in intensive care units. Journal of Anesthesia 2013 Aug;27(4):541-9 ; PMID: 23475475 ; DOI: 10.1007/s00540-013-1557-0

Lee J, Morishima T, Kunisawa S, Sasaki N, Otsubo T, Ikai H, Imanaka Y. Derivation and validation of in-hospital mortality prediction models in ischaemic stroke patients using administrative data. Cerebrovascular Diseases 2013 35(1):73-80. ; PMID: 23429000 ; DOI: 10.1159/000346090


Recent additions of disease severity information to Japanese administrative data (DPC data) were shown to achieve high accuracy of mortality prediction in stroke patients, thereby supporting further outcomes research.

Motohashi T, Hamada H, Lee J, Sekimoto M, Imanaka Y. Factors associated with prolonged length of hospital stay of elderly patients in acute care hospitals in Japan: a multilevel analysis of patients with femoral neck fracture. Health Policy 2013 111(1):60-7. ; PMID: 23628484 ; DOI: 10.1016/j.healthpol.2013.03.014


Tanaka M, Lee J, Ikai H, Imanaka Y. Development of efficiency indicators of operating room management for multi-institutional comparisons. Journal of Evaluation in Clinical Practice 2013 19(2):335-41. ; PMID: 22332870 ; DOI: 10.1111/j.1365-2753.2012.01829.x


Lee J, Morishima T, Park S, Otsubo T, Ikai H, Imanaka Y. The association between health care spending and quality of care for stroke patients in Japan. Journal of Health Services Research & Policy 2013 18(2): 77-82. ; DOI: 10.1177/1355819612473454


Testing the associations between spending and quality of care revealed that lower spending regions were associated with reduced performance in processes, but not with in-hospital mortality in ischemic stroke care.

Morishima T, Ikai H, Imanaka Y. Cost-effectiveness analysis of omalizumab for the treatment of severe asthma in Japan and the value of responder prediction methods based on a multinational trial. Value in Health Regional Issues 2013 2(1): 29–36. ; DOI: 10.1016/j.vhri.2013.01.007


We conducted an economic evaluation of omalizumab in patients with severe asthma and estimated the expected value of perfect information of responder prediction methods.

Morishima T, Lee J, Otsubo T, Ikai H, Imanaka Y. Impact of hospital case volume on quality of end-of-life care in terminal cancer patients. Journal of Palliative Medicine 2013 16(2):173-8. ; PMID: 23140184 ; DOI: 10.1089/jpm.2012.0361


We demonstrated an association between quality of end-of-life care and case volume, using a large-scale insurance claims database.

Morishima T, Imanaka Y, Otsubo T, Hayashida K, Watanabe T, Tsuji I. Burden of household environmental tobacco smoke on medical expenditure for Japanese women: a population-based cohort study. Journal of Epidemiology 2013 23(1):55-62. ; PMID: 23183111 ; DOI: 10.2188/jea.JE20120072


This is a long-term cohort study that assessed the excess in healthcare spending caused by environmental tobacco smoke in homes.

Morishima T, Otsubo T, Gotou E, Kobayashi D, Lee J, Imanaka Y. Physician adherence to asthma treatment guidelines in Japan: focus on inhaled corticosteroids. Journal of Evaluation in Clinical Practice 2013 19(2):223-9. ; PMID: 21689218 ; DOI: 10.1111/j.1365-2753.2011.01708.x


We explored the determinants of prescription of inhaled corticosteroids for patients with asthma, using an insurance claims database.

Hamada H, Sekimoto M, Imanaka Y. Effects of the per diem prospective payment system with DRG-like grouping system (DPC/PDPS) on resource usage and healthcare quality in Japan. Health Policy 2012 107(2-3):194-201. ; PMID: 22277879 ; DOI: 10.1016/j.healthpol.2012.01.002

Kunisawa S, Ikai H, Imanaka Y. Incidence and prevention of postoperative venous thromboembolism: are they meaningful quality indicators in Japanese health care settings? World Journal of Surgery 2012 36(2):280-6. ; PMID: 21879424 ; DOI: 10.1007/s00268-011-1229-x

Ikai H, Morimoto T, Shimbo T, Imanaka Y, Koike K. Impact of postgraduate education on physician practice for community-acquired pneumonia. Journal of Evaluation in Clinical Practice 2012 18(2):389-95. ; PMID: 21208347 ; DOI: 10.1111/j.1365-2753.2010.01594.x

Umegaki T, Ikai H, Imanaka Y. The impact of acute organ dysfunction on patients' mortality with severe sepsis. Journal of Anaesthesiology, Clinical Pharmacology 2011 27(2):180-4. ; PMID: 21772676 ; DOI: 10.4103/0970-9185.81816

Fukuda H, Lee J, Imanaka Y. Costs of hospital-acquired infection and transferability of the estimates: a systematic review. Infection 2011 39(3):185-99. ; PMID: 21424853 ; DOI: 10.1007/s15010-011-0095-7


A systematic review showed that only <10% of studies that produced cost estimates of HAIs had a high level of transferability, with reported cost components and unit costs.

Umegaki T, Sekimoto M, Imanaka Y. Impact of intensive care unit physician on care processes of patients with severe sepsis in teaching hospitals. Journal of Anesthesia & Clinical Research. 2011 2(2):120-125. ; DOI: 10.4172/2155-6148.1000120

Lee J, Imanaka Y, Sekimoto M, Nishikawa H, Ikai H, Motohashi T; Quality Indicator/Improvement Project (QIP) Expert Group for Clinical Evaluation. Validation of a novel method to identify healthcare-associated infections. Journal of Hospital Infection 2011 77(4):316-20. ; PMID: 21277647 ; DOI: 10.1016/j.jhin.2010.11.013


Chart review analysis was used to demonstrate the high validity of an HAI identification method based on antibiotic utilization patterns in administrative data.

Otsubo T, Imanaka Y, Lee J, Hayashida K. Evaluation of resource allocation and supply-demand balance in clinical practice with high-cost technologies. Journal of Evaluation in Clinical Practice 2011 17(6):1114-21. ; PMID: 20630009 ; DOI: 10.1111/j.1365-2753.2010.01484.x


Fukuda H, Lee J, Imanaka Y. Variations in analytical methodology for estimating costs of hospital-acquired infections: a systematic review. Journal of Hospital Infection 2011 77(2):93-105. ; PMID: 21145131 ; DOI: 10.1016/j.jhin.2010.10.006


A systematic review tracked the distribution and trends in HAI cost estimation methodologies, which focused on matched comparisons, regression models, and case reviews.

Lee J, Imanaka Y, Sekimoto M, Ikai H, Otsubo T. Healthcare-associated infections in acute ischemic stroke patients from 36 Japanese hospitals: risk-adjusted economic and clinical outcomes. International Journal of Stroke. 2011 6(1): 16-24. ; PMID: 21205236 ; DOI: 10.1111/j.1747-4949.2010.00536.x


We identified HAI incidence in stroke patients based on antibiotic utilization patterns. We quantified the increases in hospital charges, length of stay, and mortality due to HAI by statistically controlling effects of the other risk factors.

Nishikawa H, Imanaka Y, Sekimoto M, Ikai H. Verification bias in assessment of the utility of MRI in the diagnosis of cruciate ligament tears. American Journal of Roentgenology 2010 195(5):W357-64. ; PMID: 20966301 ; DOI: 10.2214/AJR.10.4189

Umegaki T, Sekimoto M, Ikai H, Imanaka Y. Current anticoagulation therapy for sepsis-induced disseminated intravascular coagulation in Japan: results of multicenter study using administrative data. Journal of the Japanese Society of Intensive Care Medicine 2010 17(4):555-559. ; DOI: 10.3918/jsicm.17.555

Umegaki T, Sekimoto M, Hayashida K, Imanaka Y. An outcome prediction model for adult intensive care. Critical Care and Resuscitation : journal of the Australasian Academy of Critical Care Medicine 2010 12(2):96-103. ; PMID: 20513217

Regenbogen SE, Hirose M, Imanaka Y, Oh EH, Fukuda H, Gawande AA, Takemura T, Yoshihara H. A comparative analysis of incident reporting lag times in academic medical centres in Japan and the USA. Quality and Safety in Health Care 2010 19(6):e10-e13. ; PMID: 20194219 ; DOI: 10.1136/qshc.2008.029215

Sasaki H, Imanaka Y, Sekimoto M, Lee J, Otsubo T. Antimicrobial prescription patterns for children hospitalized with pneumonia and compliance to guidelines in Japan: a multicenter study. Journal of Evaluation in Clinical Practice 2010 16(5):987-9. ; PMID: 20626540 ; DOI: 10.1111/j.1365-2753.2009.01237.x

Sekimoto M, Imanaka Y, Shirai T, Sasaki H, Komeno T, Lee J, Yoshihara K, Ashihara E, Maekawa T. Risk-adjusted assessment of incidence and quantity of blood use in acute-care hospitals in Japan: an analysis using administrative data. Vox Sanguinis 2010 98(4):538-46. ; PMID: 20002605 ; DOI: 10.1111/j.1423-0410.2009.01290.x

Murakami G, Imanaka Y, Kobuse H, Lee J, Goto E. Patient perceived priorities between technical skills and interpersonal skills: their influence on correlates of patient satisfaction. Journal of Evaluation in Clinical Practice 2010 16(3):560-8. ; PMID: 20438604 ; DOI: 10.1111/j.1365-2753.2009.01160.x

Hayashida K, Imanaka Y, Murakami G, Takahashi Y, Nagai M, Kuriyama S, Tsuji I. Difference in lifetime medical expenditures between male smokers and non-smokers. Health Policy 2010 94(1):84-9. ; PMID: 19775772 ; DOI: 10.1016/j.healthpol.2009.08.007

Fukuda H, Imanaka Y, Hirose M, Hayashida K Impact of system-level activities and reporting design on the number of incident reports for patient safety. Quality and Safety in Health Care 2010 19(2):122-7. ; PMID: 20351160 ; DOI: 10.1136/qshc.2008.027532

Lee J, Imanaka Y, Sekimoto M, Ishizaki T, Hayashida K, Ikai H, Otubo T. Risk-adjusted increases in medical resource utilization associated with health care-associated infections in gastrectomy patients. Journal of Evaluation in Clinical Practice 2010 16(1):100-6. ; PMID: 20367820 ; DOI: 10.1111/j.1365-2753.2009.01121.x


In gastrectomy patients, we developed an HAI identification method based on antibiotic utilization patterns in administrative data, and analyzed HAI-associated increases in hospital costs, antibiotic costs, and length of stay.

Kuwabara K, Matsuda S, Fushimi K, Ishikawa KB, Horiguchi H, Hayashida K, Fujimori K. Contribution of bile duct drainage on resource use and clinical outcome of open or laparoscopic cholecystectomy in Japan. Journal of evaluation in clinical practice. 2010 16(1):31-8. ; PMID: 20367813

Kuwabara K, Matsuda S, Imanaka Y, Fushimi K, Hashimoto H, Ishikawa KB, Horiguchi H, Hayashida K, Fujimori K, Ikeda S, Yasunaga H. Injury severity score, resource use, and outcome for trauma patients within a Japanese administrative database. Journal of Trauma - Injury, Infection and Critical Care 2010 68(2):463-70. ; PMID: 19935111 ; DOI: 10.1097/TA.0b013e3181a60275

Kuwabara K, Matsuda S, Anan M, Fushimi K, Ishikawa KB, Horiguchi H, Hayashida K, Fujimori K. Difference in resource utilization between patients with acute and chronic heart failure from Japanese administrative database. International journal of cardiology. 2010 141(3):254-9. ; PMID: 19157584

Bech M, et al [incl. Imanaka Y]. The influence of economic incentives and regulatory factors on the adoption of treatment technologies: A case study of technologies used to treat heart attacks. Health Economics 2009 18(10):1114-1132. ; PMID: 18972326 ; DOI: 10.1002/hec.1417

Fukuda H, Imanaka Y, Ishizaki T, Okuma K,Shirai T. Change in clinical practice after publication of guidelines on breast cancer treatment. International Journal for Quality in Health Care 2009 21(5):372-8. ; PMID: 19700780 ; DOI: 10.1093/intqhc/mzp037

Nishikawa H, Imanaka Y, Sekimoto M, Hayashida K, Ikai H. Influence of verification bias on the assessment of MRI in the diagnosis of meniscal tear. American Journal of Roentgenology 2009 193(6):1596-602. ; PMID: 19933653 ; DOI: 10.2214/AJR.08.2223

Nojo T, Imanaka Y, Ishizaki T, Sekimoto M, Yoshino M, Kurosawa T, Takao H, Ohtomo K. Lung cancer incidence in middle-aged men estimated by low-dose computed tomography screening. Lung Cancer 2009 65(1):56-61. ; PMID: 19019487 ; DOI: 10.1016/j.lungcan.2008.10.004

Shirai T, Imanaka Y, Sekimoto M, Ishizaki T; QIP Ovarian Cancer Expert Group. Primary chemotherapy patterns for ovarian cancer treatment in Japan. The Journal of Obstetrics and Gynaecology Research 2009 35(5):926-34. ; PMID: 20149043 ; DOI: 10.1111/j.1447-0756.2009.01033.x

Kawasaki K, Sekimoto M, Ishizaki T, Imanaka Y. Work stress and workload of full-time anesthesiologists in acute care hospitals in Japan. Journal of Anesthesia 2009 23(2):235-41. ; PMID: 19444563 ; DOI: 10.1007/s00540-008-0736-x

Sekimoto M, Imanaka Y, Kobayashi H, Okubo T, Kizu J, Kobuse H, Mihara H, Tsuji N, Yamaguchi A; Japan Council for Quality Health Care, Expert Group on Healthcare-Associated Infection Control and Prevention. Factors affecting performance of hospital infection control in Japan. American Journal of Infection Control 2009 37(2):136-42. ; PMID: 19249641 ; DOI: 10.1016/j.ajic.2008.03.005

Hayashida K, Imanaka Y, Otsubo T, Kuwabara K, Ishikawa KB, Fushimi K, Hashimoto H, Yasunaga H, Horiguchi H, Anan M, Fujimori K, Ikeda S, Matsuda S. Development and analysis of a nationwide cost database of acute-care hospitals in Japan. Journal of Evaluation in Clinical Practice 2009 15(4):626-33. ; PMID: 19522724 ; DOI: 10.1111/j.1365-2753.2008.01063.x

Fukuda H, Imanaka Y, Hirose M, Hayashida K. Factors associated with system-level activities for patient safety and infection control. Health Policy 2009 89(1):26-36. ; PMID: 18538442 ; DOI: 10.1016/j.healthpol.2008.04.009

Fukuda H, Imanaka Y. Assessment of transparency of cost estimates in economic evaluations of patient safety programmes. Journal of Evaluation in Clinical Practice 2009 15(3):451-9. ; PMID: 19366392 ; DOI: 10.1111/j.1365-2753.2008.01033.x

Fukuda H, Imanaka Y, Kobuse H, Hayashida K, Murakami G. The subjective incremental cost of informed consent and documentation in hospital care: a multicentre questionnaire survey in Japan. Journal of Evaluation in Clinical Practice 2009 15(2):234-41. ; PMID: 19335478 ; DOI: 10.1111/j.1365-2753.2008.00987.x

Kuwabara K, Matsuda S, Fushimi K, Ishikawa KB, Horiguchi H, Fujimori K, Hayashida K. Impact of timing of cholecystectomy and bile duct interventions on quality of cholecystitis care. International Journal of Surgery 2009 7(3):243-9 ; PMID: 19376278

Kuwabara K, Matsuda S, Fushimi K, Anan M, Ishikawa KB, Horiguchi H, Hayashida K, Fujimori K. Differences in practice patterns and costs between small cell and non-small cell lung cancer patients in Japan. The Tohoku Journal of Experimental Medicine. 2009 217(1):29-35. ; PMID: 19155605

Fukuda H Imanaka Y, Hirose M, Hayashida K. Economic evaluations of maintaining patient safety systems in teaching hospitals. Health Policy 2008 88(2-3):381-91. ; PMID: 18514966 ; DOI: 10.1016/j.healthpol.2008.04.004

Kuwabara K, Imanaka Y, Matsuda S, Fushimi K, Hashimoto H, Ishikawa KB, Horiguchi H, Hayashida K, Fujimori K. Cost of open versus laparoscopic appendectomy. La Clinica Terapeutica 2008 159(3):155-63. ; PMID: 18594744

Sekimoto M, Kakutani C, Inoue I, Ishizaki T, Hayashida K, Imanaka Y. Management patterns and healthcare costs for hospitalized patients with cerebral infarction. Health Policy 2008 88(1):100-9. ; PMID: 18378349 ; DOI: 10.1016/j.healthpol.2008.01.013

Fukuda H, Imanaka Y, Hayashida K. Cost of hospital-wide activities to improve patient safety and infection control: a multi-centre study in Japan. Health Policy 2008 87(1):100-11. ; PMID: 18394745 ; DOI: 10.1016/j.healthpol.2008.02.006

Ishizaki T, Imanaka Y, Oh EH, Sekimoto M, Hayashida K, Kobuse H. Association between patient age and hospitalization resource use in a teaching hospital in Japan. Health Policy 2008 87(1):20-30. ; PMID: 18067988 ; DOI: 10.1016/j.healthpol.2007.10.007

Sekimoto M, Imanaka Y, Kobayashi H, Okubo T, Kizu J, Kobuse H, Mihara H, Tsuji N, Yamaguchi A; Japan Council for Quality Health Care, Expert Group on Healthcare-Associated Infection Control and Prevention. Impact of hospital accreditation on infection control programs in teaching hospitals in Japan. American Journal of Infection Control 2008 36(3):212-9. ; PMID: 18371518 ; DOI: 10.1016/j.ajic.2007.04.276

Kuwabara K, Matsuda S, Imanaka Y, Fushimi K, Hashimoto H, Ishikawa K. The effect of age and procedure on resource use for patients with cerebrovascular disease. Journal of Health Services Research and Policy 2008 13(1):26-32. ; PMID: 18325153 ; DOI: 10.1258/jhsrp.2007.007009

Ishizaki T, Imanaka Y, Sekimoto M, Fukuda H, Mihara Hwith the Treatment of Subarachnoid Hemorrhage Expert Group. Comparisons of risk-adjusted clinical outcomes for patients with aneurysmal subarachnoid haemorrhage across eight teaching hospitals in Japan. Journal of Evaluation in Clinical Practice 2008 14(3):416-21. ; PMID: 18373576 ; DOI: 10.1111/j.1365-2753.2007.00882.x

Kuwabara K, Imanaka Y, Matsuda S, Fushimi K, Hashimoto H, Ishikawa KB, Horiguchi H, Hayashida K, Fujimori K. The association of the number of comorbidities and complications with length of stay, hospital mortality and LOS high outlier, based on administrative data. Environmental Health and Preventive Medicine 2008 13(3):130-7. ; PMID: 19568897 ; DOI: 10.1007/s12199-007-0022-9

Kuwabara K, Imanaka Y, Matsuda S, Fushimi K, Hashimoto H, Ishikawa KB, Horiguchi H, Hayashida K, Fujimori K. Impact of age and procedure on resource use for patients with ischemic heart disease. Health Policy 2008 85(2):196-206. ; PMID: 17825454 ; DOI: 10.1016/j.healthpol.2007.07.015

Oh EH, Imanaka Y, Hayashida K, Kobuse H. Meta-analysis comparing clinical effectiveness of drug-eluting stents, bare metal stents and coronary artery bypass surgery. International Journal of Evidence-Based Healthcare 2007 5(3):296-304. ; PMID: 21631793 ; DOI: 10.1111/j.1479-6988.2007.00071.x

Fushimi K, Hashimoto H, Imanaka Y, Kuwabara K, Horiguchi H, Ishikawa KB, Matsuda S. Functional mapping of hospitals by diagnosis-dominant case-mix analysis. BMC Health Services Research 2007 7(4):50-57. ; PMID: 17425788 ; DOI: 10.1186/1472-6963-7-50

Hayashida K, Imanaka Y, Sekimoto M, Kobuse H, Fukuda H. Evaluation of acute myocardial infarction in-hospital mortality using a risk-adjustment model based on Japanese administrative data. Journal of International Medical Research 2007 35(5):590-596. ; PMID: 17900397

Hayashida K, Imanaka Y, Fukuda H. Measuring hospital-wide activity volume for patient safety and infection control: a multi-centre study in Japan. BMC Health Services Research 2007 7(9):140-146. ; PMID: 17764578 ; DOI: 10.1186/1472-6963-7-140

Hirose M, Regenbogen SE, Lipsitz S, Imanaka Y, Ishizaki T, Sekimoto M, Oh EH, Gawande AA. Lagtime in incident reporting system at a university hospital in Japan. Quality and Safety in Health Care 2007 16(2):101-4. ; PMID: 17403754 ; DOI: 10.1136/qshc.2006.019851

Evans E, Imanaka Y, Sekimoto M, Ishizaki T, Hayashida K, Fukuda H, Oh EH. Risk adjusted resource utilization for AMI patients treated in Japanese hospitals. Health Economics 2007 16(4):347-359. ; PMID: 17031780 ; DOI: 10.1002/hec.1177

Murakami G, Inoue T, Saito M. On cognitive reliability of hospital organisational environment and work performance. International Journal of Healthcare Technology and Management 2007 8(4):388-398. ; DOI: 10.1504/IJHTM.2007.013170

International Hospital Federation and World Health Organization. (Imanaka Y as the principal investigator for the Western Pacific Region) A Global Study on Experiences in Hospital Sector Reform: The performance of hospitals under changing socio-economic conditions. WHO 2007

Kuwabara K, Imanaka Y, Matsuda S, Fushimi K, Hashimoto H, Ishikawa KB, Horiguchi H. Profiling of resource use variation among six diseases treated at 82 Japanese special functioning hospitals, based on administrative data. Health Policy 2006 78(2-3):306-18 ; PMID: 16343686 ; DOI: 10.1016/j.healthpol.2005.11.006

Sekimoto M, Imanaka Y, Kitano N, Ishizaki T, Takahashi O. Why are physicians not persuaded by scientific evidence? A grounded theory interview study. BMC Health Services Research 2006 6(7):92-100. ; PMID: 16872522 ; DOI: 10.1186/1472-6963-6-92

Sekimoto M, Imanaka Y, Hirose M, Ishizaki T, Murakami G, Fukata Y; QIP Cholecystectomy Expert Group. Impact of treatment policies on patient outcomes and resource utilization in acute cholecystitis in Japanese hospitals. BMC Health Services Research 2006 6(3):40-46. ; PMID: 16569249 ; DOI: 10.1186/1472-6963-6-40

Ishizaki T, Yoshida H, Suzuki T, Watanabe S, Niino N, Ihara K, Kim H, Fujiwara Y, Shinkai S, Imanaka Y. Effects of cognitive function on functional decline among community-dwelling non-disabled older Japanese. Archives of Gerontology and Geriatrics 2006 42(1):47-58. ; PMID: 16081171 ; DOI: 10.1016/j.archger.2005.06.001

Kuwabara K, Imanaka Y, Ishizaki T. Quality and productive efficiency in simple laceration treatment. Journal of Evaluation in Clinical Practice 2006 12(2):164-173. ; PMID: 16579825 ; DOI: 10.1111/j.1365-2753.2006.00597.x

Ishizaki T, Kai I, Imanaka Y. Self-rated health and social role as predictors for 6-year total mortality among a non-disabled older Japanese population. Archives of Gerontology and Geriatrics 2006 42(1):91-99. ; PMID: 16046010 ; DOI: 10.1016/j.archger.2005.05.002

Sekimoto M, et al. JPN Guidelines for the management of acute pancreatitis: epidemiology, etiology, natural history, and outcome predictors in acute pancreatitis. Journal of hepato-biliary-pancreatic surgery 2006 2006;13(1):10-24. ; PMID: 16463207

Hayashida K, Imanaka Y. Inequity in the price of physician activity across surgical procedures. Health Policy 2005 74(1):24-38. ; PMID: 16098409 ; DOI: 10.1016/j.healthpol.2004.12.005

Hirose M, Imanaka Y, Ishizaki T, Sekimoto M, Harada Y, Kuwabara K, Hayashida K, Oh EH, Evans SE. Profiling hospital performance of laparoscopic cholecystectomy based on the administrative data of four teaching hospitals in Japan. World Journal of Surgery 2005 29(4):429-435. ; PMID: 15770381 ; DOI: 10.1007/s00268-004-7535-9

Oh EH Imanaka Y, Evans E. Determinants of the diffusion of computed tomography and magnetic resonance imaging. International Journal of Technology Assessment in Health Care 2005 21(1):73-80. ; PMID: 15736517 ; DOI: 10.1017/s0266462305050099

Sekimoto M, Imanaka Y, Evans E, Ishizaki T, Hirose M, Hayashida K, Fukui T. Practice variation in perioperative antibiotic use in Japan. International Journal for Quality in Health Care 2004 16(5):367-373. ; PMID: 15375097 ; DOI: 10.1093/intqhc/mzh066

Ishizaki T, Imanaka Y, Oh E, Kuwabara K, Hirose M, Hayashida K, Harada Y. Association of hospital resource use with comorbidity status and patient age among hip fracture patients in Japan. Health Policy 2004 69(2):179-187. ; PMID: 15212865 ; DOI: 10.1016/j.healthpol.2003.12.018

Ishizaki T, Imanaka Y, Hirose M, Hayashida K, Kizu M, Inoue A, Sugie S. Estimation of the impact of providing outpatients with information about SARS infection control on their intention of outpatient visit. Health Policy 2004 69(3):293-303. ; PMID: 15276309 ; DOI: 10.1016/j.healthpol.2004.04.008

Sekimoto M, Asai A, Ohnishi M, Nishigaki E, Fukui T, Shimbo T, Imanaka Y. Patients' preferences for involvement in treatment decision making in Japan. BMC Family Practice 2004 5(1):1-10. ; PMID: 15053839 ; DOI: 10.1186/1471-2296-5-1

Ishizaki T, Kai I, Kobayashi Y, Matsuyama Y, Imanaka Y. The effect of aging on functional decline among older Japanese living in a community: a 5-year longitudinal data analysis. Aging Clinical and Experimental Research 2004 16(3):233-239. ; PMID: 15462467

Hirose M, Imanaka Y, Ishizaki T, Evans E. How can we improve the quality of health care in Japan? Learning from JCQHC hospital accreditation. Health Policy 2003 66(1):29-49 ; PMID: 14499164

Imanaka Y. Macro and micro costing of atherosclerosis-related diseases in the Japanese health care system. Atherosclerosis. 2003 4(2):189-190. ; DOI: 10.1016/S1567-5688(03)90813-0

Ishizaki T, Yoshida H, Kumagai S, Watanabe S, Shinkai S, Suzuki T, Shibata H, Imanaka Y. Active life expectancy based on activities of daily living for older people living in a rural community in Japan. Geriatrics and Gerontology International 2003 3:S78-S82. ; DOI: 10.1111/j.1444-0594.2003.00099.x

Imanaka Y, Hayashida K, Nakatani I, Kuwabara K. Validation of a theory-based costing methodology through simulation in a virtual hospital: Towards a standardized model of patient-level costing with two-dimensional components. The Proceedings of 4th World Congress of International. Health Economics Association. 2003 4:54-55.

Sekimoto M, Imanaka Y. Practice variation in perioperative antibiotic prophylaxis in Japan. The Proceedings of 20th ISQua International Conference on Quality in Health Care, Dallas. 2003 20:54-55.

Hirose M, Imanaka Y, Ishizaki T, Sekimoto M, Harada Y, Kuwabara K, Hayashida K, Oh EH, Evans E. Profiling hospital performance of laparoscopic cholecystectomy based on administrative data. World journal of surgery 2003 29(4):429-35 ; PMID: 15770381 ; DOI: 10.1007/s00268-004-7535-9

Pierre Moise, Stéphane Jacobzone and the ARD-IHD Experts Group [incl. Imanaka Y, Ishizaki T, Ogawa T] OECD Study of Cross-National Differences in the Treatment, Costs and Outcomes of Ischaemic Heart Disease (OECD Health Working Papers NO.3) OECD 2003 ; DOI: 10.1787/18152015

Pierre Moise, Stéphane Jacobzone and the ARD-IHD Experts Group [incl. Imanaka Y]. OECD Study of Cross-national Differences in the Treatment, Costs and Outcomes of Ischaemic Heart Disease (OECD Health Working Papers NO.3) - Annex 1: Tables & Charts. OECD 2003 ; DOI: 10.1787/18152015

Pierre Moise, Stéphane Jacobzone and the ARD-IHD Experts Group [incl. Imanaka Y]. OECD Study of Cross-national Differences in the Treatment, Costs and Outcomes of Ischaemic Heart Disease (OECD Health Working Papers NO.3) - Annex 2: Charts. OECD 2003 ; DOI: 10.1787/18152015

Lynelle Moon, Pierre Moise, Stéphane Jacobzone and the ARD-Stroke Experts Group [incl. Imanaka Y, Ishizaki T, Ogawa T] Stroke Care in OECD Countries: A Comparison of Treatment, Costs and Outcomes in 17 Countries (OECD Health Working Papers NO.5) OECD 2003 ; DOI: 10.1787/18152015

Lynelle Moon, Pierre Moise, Stéphane Jacobzone and the ARD-Stroke Experts Group. Stroke Care in OECD Countries: A Comparison of Treatment, Costs and Outcomes in 17 Countries (OECD Health Working Papers NO.5) – Annex OECD 2003 ; DOI: 10.1787/18152015

Tokunaga J, Imanaka Y. Influences of length of stay on patient satisfaction with hospital care in Japan. International Journal for Quality in Health Care 2002 14(6):493-502. ; PMID: 12515335

Ishizaki T, Imanaka Y, Hirose M, Kuwabara K, Ogawa T, Harada Y. A first look at variations in use of breast-conserving surgery at five teaching hospitals in Japan. International Journal for Quality in Health Care 2002 14(5):411-8. ; PMID: 12389807

Rahman M, Sekimoto M, Hira K, Koyama H, Imanaka Y, Fukui T. Is Bacillus Calmette-Guerin revaccination necessary for Japanese children? Preventive Medicine 2002 35(1):70-7 ; PMID: 12079443

Akamizu T, Nakao K, Imanaka Y. Economic evaluation of female hormone replacement therapy for osteoporosis and fractures in elderly women. Japanese Journal of Health Economics and Policy 2002 11:23-42.

Ishizaki T, Kai I, Kobayashi Y, Imanaka Y. Functional transitions and active life expectancy for older Japanese living in a community. Archives of Gerontology and Geriatrics 2002 35(2):107-20. ; PMID: 14764349

Hayashida K, Nagasue I, Fukuda T, Gunji A. The natural history model of hepatitis C virus infection and the economic evaluation of alpha interferon treatment. Journal of Epidemiology 2002 12(1):22-32. ; PMID: 11848181

Ishizaki T. Maintaining and improving health status in an aged society. Aging and Health: An International Symposium

Jee-Hughes M, Jacobzone S with the OECD study collaborative expert group [incl. Imanaka Y]. OECD study of cross-national differences in the treatment, costs and outcomes of breast cancer. OECD 2001 (web site)

WHO Study WPRO Expert Group (Imanaka Y as the principal investigator for the Western Pacific Region). Hospitals within healthcare systems: Their capacity to meet the needs of populations - Western Pacific Region. WHO 2001

The Technological Change in Health Care Research Network [incl. Imanaka Y]. Differences in technological change around the world: Evidence from heart attack care. Health Affairs 2001 20(3):25-42.

Ishizaki T, Watanabe S, Suzuki T, Shibata H, Haga H. Predictors for functional decline among nondisabled older Japanese living in a community during a 3-year follow-up. Journal of the American Geriatrics Society 2000 48(11):1424-9. ; PMID: 11083318

Tokunaga J, Imanaka Y, Nobutomo K. Effects of patient demands on satisfaction with Japanese hospital care. International Journal for Quality in Health Care 2000 12(5):395-401. ; PMID: 11079219

Imanaka.Y. Casemix refinement by extracting and integrating multi-dimensional severity information from routine data. Casemix Quarterly 2000 2:21-24. (PDF)