Ethics approval and consent to participate
We used only the existing data aggregated by prefecture of Japan. The analysis is based solely on aggregated values by prefecture and does not identify individual patients or institutions. The National Database data used in this study have already been anonymized in accordance with the Act on Assurance of Medical Care for Elderly People in Japan. According to Japan's Act on the Protection of Personal Information and Ethical Guidelines for Medical and Biological Research Involving Human Subjects, this study did not require approval by the Institutional Review Board as it uses only information that has already been anonymized. Permission was obtained from the Minister of Health, Labour and Welfare of Japan to use the National Database data. All public data except the National Database data were used, which are widely available on the Internet.
Consent for publication
Not applicable.
Availability of data and materials
The National Database data that support the findings of this study are available from Ministry of Health, Labour, and Welfare of Japan but restrictions apply to the availability of these data, which were used under license for the current study, and so are not publicly available. Data are however available from the authors upon reasonable request and with permission of Ministry of Health, Labour, and Welfare of Japan. All public data except the National Database data generated or analysed during this study are included in this published article. We provide the reference link of the public data from which the data is sourced.
The number of people per household from Portal Site of Official Statistics of Japan at www.e-stat.go.jp/stat-search/files?page=1&layout=datalist&toukei=00200241&tstat=000001039591&cycle=7&year=20170&month=0&tclass1=000001039601&stat_infid=000031598550&result_back=1&tclass2val=0.
The percentage of elderly couple households from Portal Site of Official Statistics of Japan at www.e-stat.go.jp/stat-search/files?page=1&layout=datalist&toukei=00200521&tstat=000001080615&cycle=0&tclass1=000001124175&stat_infid=000031784285&tclass2val=0.
The percentage of elderly single-person households from Portal Site of Official Statistics of Japan at www.e-stat.go.jp/stat-search/files?page=1&layout=datalist&toukei=00200521&tstat=000001011777&cycle=0&tclass1=000001011805&stat_infid=000001086178&tclass2val=0.
The national medical expenses per person from Ministry of Heath, Labour and Welfare in Japan at www.mhlw.go.jp/toukei/saikin/hw/k-iryohi/17/index.html.
The number of home care support clinics from Portal Site of Official Statistics of Japan at www.e-stat.go.jp/stat-search/files?page=1&layout=datalist&toukei=00450021& tstat=000001030908&cycle=7&tclass1=000001123595&tclass2=000001123598&stat_infid=000031780760&tclass3val=0.
The number of home care support hospitals from Portal Site of Official Statistics of Japan at www.e-stat.go.jp/stat-search/files?page=1& layout=datalist&toukei=00450021&tstat=000001030908&cycle=7&tclass1=000001123595&tclass2=000001123598&stat_infid=000031780720&tclass3val=0.
The number of visiting nursing stations from Ministry of Heath, Labour and Welfare in Japan at www.mhlw.go.jp/toukei/saikin/hw/kaigo/service17/index.html.
The number of acute care beds from Ministry of Heath, Labour and Welfare in Japan at www.mhlw.go.jp/stf/shingi2/0000196043_00001.html.
The number of long-term care beds from Portal Site of Official Statistics of Japan at www.e-stat.go.jp/stat-search/files?page=1&layout=datalist&toukei=00450023&tstat=000001030749&cycle=7&tclass1=000001123703& tclass2=000001123711&tclass3=000001123712&stat_infid=000031781159&tclass4val=0.
The number per 100,000 population of prefectures from Portal Site of Official Statistics of Japan at www.e-stat.go.jp/stat-search/files?page= 1&query=%E4%BA%BA%E5%8F%A3%E6%8E%A8%E8%A8%88%E3%80%80%E9%83%BD%E9%81%93%E5%BA%9C%E7%9C%8C%E3%80%80%E5%B9%B3%E6%88%9029&layout=dataset&stat_infid=000031690317.
The Standardized Claim-data Ratio from Cabinet Office in Japan at www5.cao.go.jp/keizai-shimon/kaigi/special/reform/mieruka/tiikisa.html.
Competing interests
The authors declare that they have no competing interests.
Funding
This work was supported by the Japan Society for the Promotion of Science Grant-in-
Aid for Scientific Research [Grant-in-Aid for Scientific Research (C), Grant Number
JP19K10550]. The funders had no role in study design, data collection and analysis,
decision to publish, or preparation of the manuscript.
Authors' contributions
All authors made substantial contributions to the concept and design of the study. KF provided expert knowledge on the data analysis, and KT performed the data analyses and developed the tables. TO, HC and YM together interpreted the results. KT wrote the first manuscript draft, all authors revised it critically, and all authors read and approved the final version.
Acknowledgments
We want to thank Dr. Jimpei Misawa for providing helpful advice for this study.