Association Between Floor of Residence and Frailty in Walk-Up Buildings Among Functionally Independent Older Adults: A Cross-Sectional Study

Background/Objectives: Frailty has been associated with various physical, psychological, and social factors; however, the influence of the residential environment—particularly walk-up buildings without elevators—remains unclear. This study aimed to examine the association between the floor of residence and frailty among functionally independent older adults. Methods: A total of 793 older adults (mean age: 76.46 ± 6.29 years; 58.83% women) living in walk-up buildings without elevators and not certified as requiring long-term care participated in a questionnaire survey. Frailty was assessed using the Kihon Checklist (KCL) and the FRAIL Scale (FS). Logistic regression analyses were conducted to examine the association between floor of residence and frailty status (non-frail vs. frail), adjusting for potential confounders. Sensitivity analyses were performed using stratified models based on age group, functional status, and living conditions. Results: Frailty prevalence was 23.28% (KCL) and 16.88% (FS). Higher floor of residence was significantly associated with lower odds of frailty (KCL: odds ratio OR = 0.82, 95% confidence interval CI: 0.69–0.97; FS: OR = 0.80, 95% CI: 0.65–0.97). Stratified analyses showed consistent associations in subgroups including those aged ≥ 75 years, with full Instrumental Activities of Daily Living scores, non-homebound status, poor subjective economic status, and living alone (all p < 0.05). Conclusions: Living on higher floors in walk-up buildings without elevators may be protective against frailty among functionally independent older adults. While barrier-free environments are essential for those with functional decline or disabilities, moderate physical challenges such as stairs may contribute to frailty prevention in populations who maintain independence.