NEW YORK, Nov 29: Increasing physical activity in midlife or later may reduce the risk of developing Alzheimer’s and other forms of dementia by up to 45%, according to a new study published in JAMA Network Open.

Researchers at the Boston University School of Public Health analyzed data from over 4,300 participants in the Framingham Heart Study Offspring, all dementia-free at the start of the study. Participants completed questionnaires reporting their levels of physical activity — sedentary, slight, moderate, or heavy — as well as sleep habits.

The study examined physical activity across three life stages: early adulthood (ages 26-44), midlife (45-64), and late life (65-88). Participants were followed for an average of 37.2, 25.9, and 14.5 years, respectively, to monitor the onset of Alzheimer’s and other dementias.

Findings revealed that individuals in the top two quintiles of midlife physical activity had a 40% lower all-cause dementia risk over 26 years compared with those with the lowest activity levels. Higher late-life physical activity was linked to a 36% to 45% lower dementia risk over 15 years.

“These results may help to inform more precise and effective strategies to prevent or delay the onset of dementia in later life and support evidence that the benefits of physical activity on the brain may extend to earlier in life than previously thought,” said Phillip Hwang, Ph.D., from the Department of Epidemiology at Boston University School of Public Health.

The study also highlighted that higher midlife activity was associated with lower dementia risk only in individuals without the APOE4 gene, a known genetic risk factor for Alzheimer’s. Late-life activity, however, reduced dementia risk in both APOE4 carriers and non-carriers.

Hwang explained that physical activity may lower dementia risk by improving brain structure and function, reducing inflammation, enhancing vascular health, and directly affecting Alzheimer’s pathology, including the accumulation of toxic beta-amyloid in the brain.

Dr. Cathryn Devons, M.D., a geriatric medicine specialist at Phelps Hospital, Northwell Health, said exercise also lowers risks for hypertension, stroke, diabetes, and other circulatory problems that can impact brain health. She added that physical activity helps reduce inflammation, further protecting cognitive function.

The researchers noted one limitation of the study: physical activity levels were self-reported, and early adulthood activity was not significantly linked to later dementia risk, possibly due to a small number of cases in that age group.

“While we can say from these results that higher levels of overall physical activity are associated with reduced dementia risk, these results cannot translate directly into recommendations about specific types of exercise,” Hwang said.

The study underscores the role of regular physical activity in potentially preventing or delaying dementia and offers guidance for personalized strategies to protect brain health.