Social hospitalization is defined as an unnecessary inpatient service that has been regarded as responsible for increased healthcare expenditure in Japan in the context of an ageing population, though the impact and the trend over time of social hospitalization has not been empirically assessed on a nationwide basis to date. It is the aim of this study to fill this knowledge gap.

The subjects are inpatients aged 65 or older who were in general or long-term care beds in the period from 1996 to 2008. "Social hospitalization in general beds" was operationalized as an inpatient care service provided at charge per day lower than the criteria price based on the Guideline for Planning Community-based Health Care. The proportion of social hospitalization was estimated using the Survey of Medical Care Activities in Public Health Insurance, and was multiplied by the daily number of inpatients derived from the Patient Survey and the average charge of socially hospitalized patients to obtain the sum of charge. The socially hospitalized patients in long-term care beds were defined as "those who could be discharged if an appropriate situation were met" as described in the Patient Survey. The daily charge of socially hospitalized patients in long-term care beds was separately obtained for those covered by health insurance and those by long-term care insurance.

Estimated results indicated that the total annual charge of social hospitalization increased from 422.8 billion yen in 1996 to 668.4 billion yen in 2002, and then declined. There was a particularly large decrease from 599.9 billion yen in 2005 to 391.1 billion yen in 2008 that corresponded to the reorganization of long-term care beds after the Ministry of Health Labour and Welfare made a policy change.