Regional Factors and Ambulatory Care-Sensitive Condition Hospitalizations in Older Japanese Adults.

Importance: Hospitalization in older adults leads to a decline in daily living activities, and countries experiencing demographic aging face an increase in hospitalization rates and health care costs. Health care systems that can reduce the probability of ambulatory care-sensitive condition (ACSC) hospitalization among older populations are needed. Objective: To comprehensively assess the association between regional factors and the probability of ACSC hospitalization among older adults and the extent to which regional factors explain this probability. Design, Setting, and Participants: A retrospective cohort study in Hokkaido prefecture, Japan, focused on participants aged 65 years or older who were covered by community-based or older-age health insurance (all adults aged 72 years and older) and had at least 2 medical visits between July and December 2022. The patients were followed up until December 2023. Exposure: Explanatory variables included municipal-level factors of residence categorized according to the Andersen behavioral model, which conceptualizes health service use as a function of predisposing, enabling, and need factors. At the municipal level, 9 predisposing, 11 enabling, and 10 need factors were included. Main Outcomes and Measures: The primary outcome was the binary variable of whether an individual was hospitalized for ACSCs between January and December 2023. Results: Among the 1 272 960 participants (median [IQR] age, 78 [73-84] years; 762 118 [59.9%] women), 51 623 (4.1%) had ACSC hospitalizations: 9492 for acute conditions, 41 271 for chronic conditions, and 3779 for vaccine-preventable conditions. A multilevel logistic regression analysis with individuals for level 1 and municipalities for level 2 revealed that 6.0% of the variance was attributable to municipal factors. Lower odds of hospitalization were associated with more clinics (odds ratio [OR], 0.933; 95% CI, 0.881-0.988), long-term care rehabilitation beds (OR, 0.996; 95% CI, 0.993-0.999), and higher financial power (OR, 0.359; 95% CI, 0.236-0.548); home care support clinics showed a similar direction (OR, 0.807; 95% CI, 0.636-1.024). Higher odds were associated with more nursing home beds (OR, 1.004; 95% CI, 1.000-1.009), a higher proportion of older adults living alone (OR, 1.073; 95% CI, 1.032-1.116), and a higher income (OR, 1.0004; 95% CI, 1.0001-1.0006). Conclusions and Relevance: In this cohort study of older adults in Japan, ACSC hospitalizations were less likely in municipalities with more outpatient, in-home, and rehabilitation care resources and stronger financial capacity and more likely in those with more nursing home beds, greater social isolation, and higher income levels.