Though there's no such thing as a bad time to exercise, your brain might thank you if you especially commit during these years.
As you age, it’s natural to hope that the years ahead will bring wisdom, comfort, and time to enjoy the people and activities you love. Dementia, a progressive brain disease affecting about one in 10 American seniors, according to Columbia University medical experts, too often robs older adults of that possibility. The condition slowly erodes memory, judgment, and independence—not only reshaping not only the lives of those diagnosed but also the families and caregivers who support them. It also significantly impacts broader health and longevity.
While not all cases of dementia are preventable, experts say that lifestyle factors do indeed play a role in your risk level. Following a healthy diet, staying connected to others, managing weight, quitting smoking, and more can all help you make meaningful strides toward better brain health.
Exercise is another crucial piece of the puzzle. Published in JAMA Network Open, a November 2025 study examined how physical activity across different stages of adulthood relates to the risk of developing dementia. It found that staying active during certain life stages could reduce dementia risk by nearly half.
The study’s researchers, a team of Boston University neurobiologists, tracked the physical activity and health data of more than 4,000 participants who were initially free of dementia. Three age cohorts were included in the study:
- Early adulthood (average age of 36)
- Midlife (average age of 54)
- Later life (average age of 71)
Using a composite physical activity index, the investigators then grouped participants into fifths—ranging from the lowest to highest activity levels—and followed them for up to several decades to identify new cases of all-cause dementia and Alzheimer’s disease. Overall, 567 cases of dementia were identified across the decades of observation.
The team found that individuals in the highest activity groups during these periods experienced roughly 41% to 45% lower risk of all-cause dementia compared with those in the least active groups—and the results pointed to clear age-specific patterns. Exercise in midlife (ages 45 to 64) and late life (ages 65 to 88) had strong protective associations with dementia risk.
In a Boston University news release, lead author Francesca Marino, PhD, says there’s a reasonable explanation behind this: “Physical activity helps improve our brain structure and function and may also directly lower the amount of Alzheimer’s disease neuropathology, such as amyloid-beta and tau. It can also help lower inflammation and improve our cardiovascular health by lowering blood pressure or reducing the risk of diabetes, for example.”
These patterns were similar when the researchers examined Alzheimer’s disease specifically. In contrast, activity levels reported in early adulthood did not demonstrate a measurable relationship with later-life dementia outcomes, though researchers point out they may not have the necessary follow-up health details on those individuals at this stage.
While being active at any age confers broad health benefits, this study suggests that maintaining regular physical activity from middle age onward may be particularly important for preserving cognitive health.
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