Exercise Boosts Brain Size, Reduces Dementia Risk

Researchers using the Framingham Heart Study have found a link between less physical activity and greater risk of developing dementia.

While multiple longitudinal studies have determined an inverse relationship between physical activity levels and cognitive decline, dementia, and/or Alzheimer disease (AD), results have been inconsistent, according to a team of investigators who followed cases of patients in an older, community-based cohort for more than a decade in an effort to examine the connection between physical activity and the risk of incident dementia and subclinical brain magnetic resonance imaging markers of dementia. 
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To do so, the authors assessed the physical activity index (PAI) in the Framingham Study Original and Offspring cohorts, aged 60 years or older, evaluating the association between PAI and risk of incident all-cause dementia and AD in participants of both cohorts who were cognitively intact and had available PAI. Overall, the researchers studied 3714 individuals and also examined the association between PAI and brain magnetic resonance imaging in the Offspring cohort.

Over a decade of follow-up, 236 participants developed dementia, of whom 188 developed AD. Participants in the lowest quintile of PAI had an increased risk of incident dementia compared with those in higher quintiles in a multivariable-adjusted model. Secondary analysis revealed that this relationship was limited to participants who were apolipoprotein E ε4 allele noncarriers and was strongest in participants aged 75 years or older. PAI was also linearly related to total brain and hippocampal volumes.

These results "add to the evidence base that regular physical activity can reduce one's risk for AD and other forms of dementia and fights against the age-related reduction in brain size," said lead study author Zaldy S. Tan, MD, MPH, medical director of the Alzheimer's and Dementia Care Program at the University of California Los Angeles (UCLA).

The findings "are very encouraging, in that even moderate physical activity [reaps] beneficial effects, especially in people over the age of 75," said Dr Tan, who is also an associate professor at UCLA's David Geffen School of Medicine. "This means that one is never too old to gain brain health benefits from exercise."

Even "a little activity appears to be better than nothing," added Nicole L. Spartano, PhD, a postdoctoral fellow at Boston University School of Medicine in Massachusetts and a coauthor of the study.

"Our data also suggests that the activity might not have to be very strenuous, which may be a good message to hear for older adults with mobility issues or worries about their safety in strenuous exercise," Dr Spartano said. "This study suggests that it is the total picture of improving the healthy lifestyle, which may involve getting out and gardening, going for a walk around the block with a neighbor, or [doing] light exercises in the home."

—Mark McGraw

Reference

Tan ZS, Spartano NL, Beiser AS et al. Physical activity, brain volume, and dementia risk: the Framingham Study [published online July 15, 2016]. J Gerontol A Biol Sci Med Sci. doi:10.1093/gerona/glw130.