Incidence and factors associated with unplanned hospital return within 6 months in frail older adults in Thailand

Unplanned hospital return after discharge is common among frail older adults, but evidence on its incidence, risk factors, and economic burden in Southeast Asia is limited. We evaluated these outcomes after discharge from medical wards. To determine 6-month cumulative unplanned hospital return, identify associated factors at 1, 3, and 6 months, and estimate its economic burden from a societal perspective. This secondary analysis used interim prospective data from an ongoing randomized controlled trial at a university hospital. Frail patients aged ≥ 60 years admitted to medical wards were followed for 1, 3, and 6 months after discharge. Unplanned hospital returns were defined as emergency department visits, unplanned outpatient visits, and hospital readmissions. Multivariable logistic regression analyses were performed to identify factors associated with unplanned hospital return at each follow-up period. Direct medical costs (DMCs) and direct non-medical costs (DNMCs) over 6 months were compared according to unplanned hospital return status. Among 170 frail older adults, the cumulative incidence of unplanned hospital return was 34.7% at 1 month, increasing to 55.3% at 3 months and 64.7% at 6 months. In the primary 6-month analysis, better nutritional status was associated with lower odds of return, aOR 0.83, 95% CI 0.72–0.97. At 3 months, better nutritional status was associated with lower odds, aOR 0.85, 95% CI 0.74–0.98, while in-hospital heart failure was associated with higher odds, aOR 2.36, 95% CI 1.05–5.34. At 1 month, higher depressive symptom scores were associated with increased odds in sensitivity analysis, aOR 1.08, 95% CI 1.02–1.15. Participants with unplanned hospital return had higher outpatient, post-discharge inpatient, and total DMCs over 6 months, while DNMCs were numerically higher but not significantly different between groups. Unplanned hospital return was common and increased over time among frail older adults. Associated factors varied across follow-up periods, highlighting the potential importance of nutritional status, heart failure, and depressive symptoms in post-discharge assessment. Participants with unplanned hospital return also had higher healthcare costs, indicating greater healthcare resource use over 6 months. The parent randomized controlled trial was registered with the Thai Clinical Trials Registry (TCTR20190910002) on 10 September 2019.