BOSTON — Adults in a long-running U.S. heart study who reported the highest levels of midlife exercise were about 40% less likely to develop dementia over roughly 26 years of follow-up, and those who stayed active into their late 60s and 70s saw risk fall by as much as 45%, according to new research from Boston University scientists. Researchers say consistent movement during the 40s, 50s, and beyond may protect the brain by boosting blood flow, reducing inflammation, and supporting healthier brain structure over time, Dec. 9, 2025.
Midlife exercise stands out as a critical window.
The new analysis, described in a JAMA Network Open paper, tracked 5,354 adults in the Framingham Heart Study Offspring cohort through early adulthood (ages 26–44), midlife (ages 45–64), and late life (ages 65–88). People in the top two quintiles of physical activity at midlife had about a 40% lower risk of all-cause dementia than those in the least active group. In comparison, the most active older adults had about a 45% lower risk.
By contrast, physical activity reported in early adulthood did not show a significant association with dementia after accounting for age, education, and cardiovascular risk factors. The pattern suggests that midlife exercise and other lifestyle choices may be essential for brain health, while high blood pressure, diabetes, and obesity tend to emerge.
In an interview about the findings, epidemiologist Phillip Hwang of Boston University School of Public Health said, “We know that increasing levels of physical activity may help to reduce dementia risk,” and noted that the data show those benefits may reach well into midlife rather than being confined to older age.
New findings fit a decades-long pattern.
The Framingham results add weight to earlier work showing that midlife exercise can have long-lasting effects on the brain. In the 2010 AGES–Reykjavik Study, Icelandic adults who reported regular physical activity in midlife performed better on memory and thinking tests decades later and were less likely to develop dementia than their less-active peers.
A 2017 Whitehall II cohort study of British civil servants, published in the journal BMJ, likewise found that participants who were physically active around midlife had a lower risk of dementia over a 28-year follow-up period than those who were inactive, even after accounting for education, smoking, and other health factors. The authors of that Whitehall II analysis argued that reverse causation—early dementia making people less active—was unlikely to fully explain the association.
Additional evidence comes from a study of women in Sweden, highlighted in a 2018 American Academy of Neurology press release, which reported that women with the highest levels of cardiovascular fitness in midlife were nearly 90% less likely to develop dementia than moderately fit women and tended to develop symptoms more than a decade later if they did. Taken together, these findings reinforce the idea that building and sustaining midlife exercise may help the brain withstand damage for longer.
What midlife exercise could look like in everyday life?
In the new Framingham study, physical activity was measured with a composite score that counted everything from walking and housework to structured workouts. That means midlife exercise did not have to be extreme: brisk walking, cycling, swimming, yard work, or active play with children all contributed to higher scores, and the strongest links with lower dementia risk came from moderate to vigorous movement done regularly rather than intense but rare sessions.
Researchers caution that the study is observational, so midlife exercise cannot be treated as a guaranteed shield against dementia, and self-reported activity may be imprecise. Still, combined with decades of research tying physical fitness to better cognitive function, the new data strengthen calls for people in their 40s, 50s, and early 60s to weave movement into daily life—taking the stairs, walking or biking for short trips, joining group exercise classes, or finding any routine that is sustainable.
For now, the message from scientists is straightforward: build and sustain midlife exercise in whatever form is realistic, and keep moving into later life. Even if staying active does not entirely prevent dementia, it may delay onset and preserve more years of clear thinking, independence, and quality of life.
