Physical activity in midlife may not reduce the risk of dementia, according to data published in the BMJ.

verine Sabia, PhD, from the Centre for Research in Epidemiology and Population Health at Hospital Paul Brousse in Paris, and colleagues conducted a prospective cohort study with a mean follow-up period of 27 years to explore the association between physical activity and the risk of dementia.

“Given rapid increases in life expectancy, dementia is increasingly a public health challenge and the need to identify modifiable risk factors that prevent or delay dementia onset has never been greater,” the study authors wrote. “Owing to its cardioprotective effect, physical activity has been put forward as a possible candidate. The evidence from our study, which examined both cognitive decline and dementia, challenges this hypothesis and provides no evidence for a neuroprotective effect.”

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The study included 10,408 participants between 33 and 55 years of age at baseline. The researchers assessed time spent in mild, moderate to vigorous, and total physical activity on 7 occasions between 1985 and 2013. “Recommended physical activity” was defined as 2.5 hours or more of moderate to vigorous physical activity per week.

The investigators observed no association between physical activity and subsequent 15-year cognitive decline. In addition, no association was found between physical activity and the risk of dementia during an average 27-year follow-up (hazard ratio for recommended physical activity, 1.00).

The authors note that physical activity in patients with dementia began to decline up to 9 years before diagnosis (difference in moderate to vigorous physical activity, -0.39 hours per week). The difference became more evident at diagnosis (-1.03 hours per week).

“Physical activity levels were lower in the years leading up to diagnosis of dementia, suggesting that changes in physical activity might simply be part of the preclinical symptoms of dementia,” the authors concluded. “We found no evidence of a slower rate of cognitive decline in people doing more physical activity.”


  1. Sabia S, Dugravot A, Dartigues JF, et al. Physical activity, cognitive decline, and risk of dementia: 28-year follow-up of Whitehall II cohort study. BMJ. 2017. doi:10.1136/bmj.j2709