More Evidence That Physical Activity Protects the Aging Brain

Megan Brooks

May 16, 2012

May 16, 2012 — 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 (AD).

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.

Their findings were published in the April 24 issue of Neurology.

Objective Activity Data

The authors of a linked editorial point out that this is the first study to report prospective associations of physical activity with AD and cognitive decline using an objective measurement of physical activity, which "importantly eliminates recall bias, and includes an all-encompassing measure of daily physical activity."

Most prior studies have consistently associated physical activity with decreased risk for cognitive decline and dementia but have relied on self-report measures of physical activity without objective validation.

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).

In a linear mixed-effect model, the level of total daily physical activity was also associated with a slower rate of global cognitive decline (estimate, 0.033 [standard error, 0.012]; P = .007), particularly for episodic memory, working memory, perceptual speed, and visuospatial abilities.

Pragmatic Implications

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.

Michal Schnaider Beeri, PhD, from the Department of Psychiatry, Mount Sinai School of Medicine in New York City, and Laura Middleton, PhD, from the Joseph Sagol Neuroscience Center, Sheba Medical Center, Tel Hashomer, Israel, agree.

"These results may have substantial pragmatic implications for public health," they write in their editorial. "Motivating the elderly to be physically active, even if mobility is limited, may decrease their risk of developing AD. Since in the Buchman et al. study the actigraph was attached to the wrist, cooking, washing dishes, playing cards, and even activity in the setting of reduced mobility, such as moving a wheelchair with one's arms, constitute nonexercise physical activity from which elderly may benefit," they note.

As for the research implications, Dr. Buchman and colleagues say, going forward, it may be particularly important to measure exercise and nonexercise activities in older adults.

"It is likely that with falling cost and technologic advances," the study authors conclude, the use of actigraphs and other devices that provide objective data "will become more commonplace, increasing the precision and specificity of physical activity measures and facilitating efforts to explicate the link between physical activity and cognition in old age."

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.

Neurology. 2012;78:1290-1291,1323-1329. Abstract Editorial

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