Abstract
To assess the directionality of the association between physical and cognitive decline in later life, we compared patterns of decline in performance across groups defined by baseline presence of cognitive and/or physical impairment [none (n = 217); physical only (n = 169); cognitive only (n = 158), or both (n = 220)] in a large sample of participants in a cognitive aging study at the Knight Alzheimer’s Disease Research Center at Washington University in St. Louis who were followed for up to 8 years (3,079 observations). Rates of decline reached 20% for physical performance and varied across cognitive tests (global, memory, speed, executive function, and visuospatial skills). We found that physical decline was better predicted by baseline cognitive impairment (slope = -1.22, p<0.001), with baseline physical impairment not contributing to further decline in physical performance (slope = -0.25, p = 0.294). In turn, baseline physical impairment was only marginally associated with rate of cognitive decline across various cognitive domains. The cognitive-functional association is likely to operate in the direction of cognitive impairment to physical decline although physical impairment may also play a role in cognitive decline/dementia. Interventions to prevent further functional decline and development of disability and complete dependence may benefit if targeted to individuals with cognitive impairment who are at increased risk.
Highlights
More than 5 mil Americans aged 65 years or older currently have Alzheimer’s disease (AD), with this figure expected to inflate to13.8 mil by 2050 [1]
Twenty eight percent of our participants were non-impaired (NI), 22.1% were physically impaired only (PI), 20.7% cognitively impaired only (CI), and 28.8% dually impaired at baseline (CPI)
While we have previously reported a higher risk of dementia in initially dementia-free community-dwelling older adults with mild physical impairment [7], physical impairment itself does not appear to be an important facilitator for cognitive decline, which is better predicted by presence of cognitive impairment
Summary
More than 5 mil Americans aged 65 years or older currently have Alzheimer’s disease (AD), with this figure expected to inflate to13.8 mil by 2050 [1]. 23.7 mil (62%) of seniors report limitations in activities of daily living (ADL) [2], rendering dementia and disability important public health concerns, especially in the context of their frequent co-existence [3]. Associations between physical performance and individual cognitive domains (e.g. cognitive speed) have been reported [4] and cross-sectional analyses support an effect of physical performance across different cognitive subdomains [5]. Physical and Cognitive Decline in Older Adults can track data requests and usage as part of the required grant reporting process and to assure the protection of rights and privacy of our research participants
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