Loss of muscle strength is common and associated with a variety of adverse health outcomes in old age, but few studies have examined the association of muscle strength with the risk of Alzheimer’s disease (AD) or mild cognitive impairment (MCI). We tested the hypothesis that muscle strength is associated with incident AD and MCI.
Prospective, observational cohort study.
Retirement communities across the Chicago metropolitan area.
More than 900 community-based older persons without dementia at the baseline evaluation and in whom strength was measured in nine muscle groups in both arms and legs as well as in the axial muscles and summarized into a composite measure of muscle strength.
Main Outcome Measures
Incident AD, MCI and rate of change in global cognitive function.
During a mean follow-up of 3.6 years, 138 persons developed AD. In a proportional hazards model adjusted for age, sex, and education, each 1 unit increase in muscle strength at baseline was associated with about a 43% decrease in the risk of AD (HR, 0.57; 95% CI, 0.41,0.79). The association of muscle strength with AD persisted even after adjustment for several covariates, including body mass index, physical activity, pulmonary function, vascular risk factors, vascular diseases and apolipoprotein E4 status. Further, in a mixed-effects model adjusted for age, sex, education, and baseline level of global cognition, increased muscle strength was associated with a slower rate of decline in global cognitive function (p<0.001). Finally, muscle strength was associated with a decreased risk of MCI, the precursor to AD (HR, 0.67; 95% CI, 0.54, 0.84).
These findings suggest a link between muscle strength, AD and cognitive decline in older persons.