Impairments in physical performance and cognitive status as predisposing factors for functional dependence among nondisabled older persons

Background. Little is known about the processes underlying the development of functional dependence. We set out to determine whether impairments in physical performance and cognitive status contribute independently to the risk of functional dependence in nondisabled older persons. Methods. Among a probability sample of 1,103 community-living adults, aged 72 years and older, we evaluated the 945 subjects who reported no disability in the activities of daily living. Subjects underwent a comprehensive assessment, including physical performance and cognitive testing. Results. Among the 775 subjects alive with complete outcomes data, 221 (28.5%) developed dependence in activities of daily living at either the 1- or 3-year follow-up interview. The rates of functional dependence were 18%, 20%, 26%, and 50% (p < .001) and 18%, 23%, 31%, and 47% (p < .001), respectively, across quarters of worsening physical performance and cognitive status. Compared with subjects in the best group, those with the worst physical performance and cognitive status were more than five times as likely to develop functional dependence (67% vs 13%; p < .001). After adjustment for age, gender, number of chronic conditions, and housing stratum, the risk of functional dependence increased across quarters of both worsening physical performance (relative risks [RR] 1.0, 1.1, 1.3, 2.1) and cognitive status (RR 1.0, 1.3, 1.5, 2.0), independent of the effect of the other. Similar results were found for subjects who developed functional dependence at one year, for those who developed functional dependence at three years, and for the combined endpoint of functional dependence or death. Conclusions. Impairments in physical performance and cognitive status contribute independently to the risk of functional dependence in nondisabled, community-living older adults. A better understanding of the processes underlying functional dependence may facilitate the design of effective and efficient strategies to prevent or slow functional decline.