Social frailty reflected by housebound status as an independent predictor of self-reported incidence fracture in community-dwelling older adults: A longitudinal cohort study

• Frailty subtypes were assessed using the Kihon Checklist in older adults. • Housebound status independently predicted future fractures in a 9-year cohort. • A single KCL item on going out weekly identified high fracture risk. • KCL may serve as a simple screening tool for fracture prevention in the community. • Findings support including social frailty in fracture risk assessment models. This study aims to determine whether frailty, assessed using the simple multidimensional frailty assessment tool, the Kihon Checklist (KCL), is associated with future fractures and, if so, to identify which frailty subtypes exhibit the strongest association with fracture incidence. This study recruited local residents who visited government-organized examination sites for specific health check-ups for older adults, conducted over a three-day period each year and 468 community-dwelling older adults from 2014 to 2023 in Hino Town, Tottori Prefecture, Japan. Characteristics, physical structure and performance, and frailty were assessed at the baseline assessment. Frailty was assessed using KCL and categorized into six subtypes: lower motor function, malnutritional, lower oral function, housebound, reduced cognitive function, and possible depression. Self-Reported incidence fracture was determined through annual follow-up surveys. Kaplan-Meier survival analysis and Cox proportional hazards models were used to evaluate the association between frailty subtypes and fracture incidence. A total of 352 participants were followed for fracture incidence over a mean period of 6.9 years. During the follow-up period, 41 participants experienced at least one fracture, resulting in an incidence rate of 1.69 per 100 person-years. Both lower motor function and housebound were significantly associated with fracture incidence. However, after adjusting for previous fall history, and lower bone mass, housebound (HR = 2.436, 95 % CI: 1.125–5.271) remained significantly associated with fracture incidence. Unlike previous studies emphasizing musculoskeletal frailty, our findings highlight housebound status as a factor associated with fractures. Fracture prevention strategies should integrate social engagement interventions alongside conventional musculoskeletal management.