Psychiatric Admissions and Length of Stay During Fiscal Years 2014 and 2015 in Japan: A Retrospective Cohort Study Using a Nationwide Claims Database

Background: A better understanding of resource use of new psychiatric admissions is important for healthcare providers and policymakers to improve psychiatric care. This study aims to describe the pattern of new psychiatric admissions and length of stay in Japan. Methods: A retrospective cohort study was conducted using data from the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB). All patients newly admitted to psychiatric wards from April 2014 through March 2016 were included and followed up until discharge to the community. Results: Our sample included 605,982 admissions from 1,621 hospitals over 2 years. The average monthly number of admissions was 25,024 in fiscal year 2014 and 25,475 in fiscal year 2015. There was a seasonal trend in the number of admissions, with a peak in summer (in July). The discharge rates within 90 days and 360 days were 64.1% and 85.7%, respectively, and varied by type of hospital fee and by hospital. For example, the range of hospital-level discharge rate within 90 days in psychiatric emergency units was 46.0-75.3% in the 1st (lowest) quintile, while it was 83.6-96.0% in the 5th (highest) quintile. The prefecture-level indicators in the NDB and the 630 survey had correlations of >0.70. Conclusions: Our study provides fundamental information on resource use of new psychiatric admissions in Japan. Although using the NDB has substantial benefits in monitoring resource use, the results should be interpreted with some caution owing to methodological issues inherent in the database.