New data from the Rush Memory and Aging Project provide more evidence that staying physically active may protect the aging brain from Alzheimer's disease.
In a group of more than 700 elderly individuals free of dementia at baseline, a higher level of total daily physical activity, determined objectively via 24-hour actigraphy, was associated with a lower risk for the subsequent development of AD, as well as a slower rate of cognitive decline.
The association remained "robust" after accounting for a wide variety of potentially confounding factors, and supports efforts to encourage physical activity even in the very old, conclude Aron S. Buchman, MD, from the Rush Alzheimer's Disease Center, Rush University Medical Center in Chicago, Illinois, and colleagues.
During the study, 716 dementia-free individuals (mean age, 82 years) wore an actigraph on the nondominant wrist 24 hours a day for up to 10 days. The device records total daily exercise and nonexercise physical activity. As part of the ongoing prospective observational Rush Memory and Aging Project, participants underwent structured annual clinical exams, including a battery of 19 cognitive tests.
Over an average of 3.5 years, 71 participants (9.9%) developed AD. According to a Cox proportional hazards model adjusted for age, sex, and education, level of total daily physical activity was associated with incident AD (hazard ratio, 0.477; 95% confidence interval, 0.273 - 0.832).
The association remained after further adjustment for self-report physical, social, and cognitive activities, as well as current level of motor function, depressive symptoms, chronic health conditions, and APOE allele status.
According to the investigators, an individual with low total daily physical activity (10th percentile) had a more than 2-fold higher risk of developing AD as compared with a participant with high total daily physical activity (90th percentile).
Dr. Buchman and colleagues say the finding that not only exercise but also higher levels of nonexercise activity are associated with cognition in old age has "important implications not only for observational studies but also for the design of physical activity intervention studies and cognition in old age. Older individuals, for whom participation in formal exercise may be constrained because of underlying health problems, may nonetheless benefit from a more active lifestyle through increases in the full spectrum of routine activities," they explain.
The findings were published in Neurology.
The study was supported by the National Institutes of Health and the National Institute on Aging, the Illinois Department of Public Health, and the Robert C. Borwell Endowment Fund. The study and editorial authors have disclosed no relevant financial relationships.