Association of cognitive status with functional limitation and disability in older adults

Background and aims: Although cognitive status is known to be associated with physical function in older people, the role it plays in the disability process is not well established. This study aimed at determining whether cognitive ability predicts functional limitations, as well as disability, and whether it is associated with the rate of change in physical functions. Methods: A community-based longitudinal study was conducted, involving 977 older persons aged 65 and older living in an urban community. Physical functions were assessed by tests scoring functional limitations (upper and lower body) and disability (activities of daily living). Cognitive function was evaluated using the Mini-Mental State Examination. Linear regression analyses with generalized estimating equations modeled the two physical function scores separately, as functions of cognitive status and time, in a one-year follow-up, controlling for sociodemographic and health-related characteristics. Results: Cognitive status independently predicted functional limitations as well as disability in older people. In addition, the strength of the association of cognitive status with physical functions increased over time, as revealed by the significant interaction between cognitive ability and time. Cognitive status influenced the rate of change in disability scores, more among women and in those aged 75 or older. The relationship was unaffected by baseline physical functional status, but was significant only among those with no cognitive impairment at baseline. Conclusions: Cognitive status appears to be a useful indicator of the disablement process in older people. It may play an important role in the development of disability, implying that strategies for early intervention to prevent the progression of disability may need to take cognitive functions into account. The increasing strength of the relationship between cognitive and physical functions over time further attests to its value in monitoring functional change.