Differential Associations of Frailty with the Incidence of Mild and Severe Disabilities in Older Adults: A 3-Year Cohort Study

Background: Frailty is associated with the incidence of disability in older adults; however, few studies have investigated differences in the association of frailty with mild and severe disabilities according to Japanese long-term care insurance certification. This study separately investigated the associations between frailty and the incidence of mild and severe disabilities. Methods: This 3-year retrospective cohort study included community-dwelling adults in Okayama City aged ≥65 years. We assessed frailty status using the Kihon Checklist and defined the outcomes as mild and severe disabilities according to long-term care insurance certifications. We applied multino-mial logistic regression analysis to investigate the association between frailty and the incidence of mild and severe disabilities. Results: The analysis included a total of 36,043 participants. For mild disability, the odds ratios (ORs) comparing frail to robust and prefrail to robust were 3.85 (95% confidence interval [CI], 3.36–4.42) and 1.82 (95% CI, 1.58–2.10), respectively. Similarly, the corresponding ORs for severe disability were 4.35 (95% CI, 3.55– 5.34) and 1.78 (95% CI, 1.43–2.21), respectively. In the age-stratified analysis of mild disability, the pre-old group (aged 65–74 years) with frail showed a higher association than the old-age group (aged ≥75 years) with frail. Regarding severe disability, the older group with frailty showed a higher association than the pre-old group with frailty. Conclusion: The results showed that both prefrail and frail were associated with the incidence of mild and severe disabilities, with different patterns of association between the pre-old and old age groups.