Variation in the Association between Frailty and Disability over 10 Years: A Cohort Study

Background: Although frailty is associated with disability, its long-term persistence and changes over time remain unclear.This study aimed to investigate the long-term association between frailty and the incidence of disability over a 10-year follow-up period, evaluating how this association changed over time.Methods: This cohort study was conducted in Okayama City, Japan.Community-dwelling older adults aged 65 years were included.Frailty was assessed using the Kihon Checklist, and disability was defined as a new certification for long-term care insurance.The association between frailty and disability was examined across five time periods (years 1-2, 3-4, 5-6, 7-8, and 9-10) using a marginal structural model with inverse probability of treatment weighting and inverse probability of censoring weighting. Results:The final analysis included 45,291 participants, with 17.3% classified as frail.The adjusted odds ratios (ORs) for the association between frailty and the incidence of disability gradually decreased over time but remained throughout the 10-year follow-up period.The adjusted ORs and 95% confidence intervals were 2.90 (2.55-3.29)for years 1-2, 2.40 (2.09-2.75)for years 3-4, 2.03 (1.76-2.34)for years 5-6, 1.75 (1.52-2.01)for years 7-8, and 1.58 (1.38-1.82)for years 9-10. Conclusion:Frailty was consistently associated with the incidence of disability over a 10-year follow-up period, with a stronger association in the earlier years and a gradual decline over time.