Is Exercise Really Neuroprotective?

Physical activity does not appear to be associated with a protective effect against dementia, according to the results of a recent study.

In order to examine the association between physical activity and dementia risk, researchers conducted a prospective cohort study of 10,308 participants, aged 35 to 55 years at inception, with a mean follow-up of 27 years.
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Physical activity was assessed 7 times between 1985 and 2013. Participants’ activity was categorized as “recommended” if the duration of moderate to vigorous activity was 2.5 hours per week or more.

Cognitive tests were conducted up to 4 times from 1997 to 2013. Overall, 329 cases of incident dementia were identified.

Mixed effects models and Cox regression both showed no association between physical activity and subsequent cognitive decline. However, levels of activity began to decline in individuals with dementia up to 9 years before diagnosis, suggesting that lower physical activity may be the result of preclinical changes. 

“This study found no evidence of a neuroprotective effect of physical activity. Previous findings showing a lower risk of dementia in physically active people may be attributable to reverse causation—that is, due to a decline in physical activity levels in the preclinical phase of dementia.” 

—Michael Potts

Reference:

Sabia S, Dugravot A, Dartigues J, et al. Physical activity, cognitive decline, and risk of dementia: 28 year follow-up of Whitehall II cohort study [ published online June 22, 2017]. doi: https://doi.org/10.1136/bmj.j2709.