Association of community welfare resources and outpatient occupational therapy with psychiatric length of stay: A nationwide analysis in Japan

Abstract Aim Japan maintains exceptionally high psychiatric bed numbers and long hospitalization durations compared to global standards. This study examined prefecture‐level associations between psychiatric bed supply, occupational therapy (OT) provision, and community welfare resources, and the average length of stay (ALOS). Methods We performed a cross‐sectional ecological analysis utilizing the 10th National Database of Health Insurance Claims (NDB) Open Data and government hospital statistics from fiscal year 2023. Dataset aggregation covered all 47 prefectures. We calculated standardized indicators per 100,000 population for psychiatric bed density, inpatient and outpatient OT claims, and community‐based disability welfare facilities. Standardized multivariate regression modeling was employed to identify variables independently associated with ALOS, strictly evaluating the contributions of regional medical and welfare systems. Results The analysis identified that psychiatric bed density was most strongly associated with longer ALOS, which is consistent with the supply‐induced demand hypothesis. Crucially, however, the regression model revealed that higher utilization rates of outpatient OT and a greater density of community‐based welfare facilities were significantly and independently associated with shorter ALOS. Conversely, the volume of inpatient OT provision did not demonstrate a significant independent effect on shortening hospital stays in the adjusted model. Conclusion At the prefectural level, psychiatric bed density was independently associated with longer ALOS, whereas outpatient OT utilization and community‐based welfare facility density were independently associated with shorter ALOS. These findings suggest that community‐based therapeutic and welfare resources may be relevant to shorter hospital stays, although causal inference is limited by the cross‐sectional ecological design.