November 26, 2025
Many studies have shown that exercise is good for the brain. But is physical activity most important earlier or later in life, and does it need to be intense? A new study offers some clues.
For the analysis, researchers at Boston University looked at more than 4,000 men and women who were part of the Framingham Heart Study Offspring cohort, a long-running multigenerational study of aging and health. None had Alzheimer’s disease or other forms of dementia at the start of the study period.
Participants were divided into three general groups, according to their age at the study’s start. The early adult group had 1,526 men and women who ranged in age from 26 to 44, and researchers followed them for an average of 37 years. The midlife group, aged 45 to 64, had 1,943 participants who were followed for an average of 26 years. And there were 885 in the late-life group, aged 65 to 88, followed for about 14 years on average.
Participants also regularly filled out detailed questionnaires about their typical physical activity levels, starting in 1971 and continuing for decades. The questionnaire asked such questions as how many days a week do you exercise or spend time doing chores or other activities such as climbing stairs or walking. It gauged intense physical activities, enough to work up a sweat, such as jogging, swimming or doing heavy yard work such as chopping wood. It also assessed levels of more moderate activities such as housework like vacuuming or dusting or lighter sports such as bowling, walking or golf.
During the study period, 567 participants developed Alzheimer’s disease or another form of dementia. The researchers considered various factors that can contribute to dementia risk, including age and education and health conditions like high blood pressure and diabetes.
They found that men and women with the highest levels of moderate or heavy physical activity in midlife were 41 percent less likely to develop dementia compared to their peers with the lowest levels of activity. Those with higher levels of physical activity later in life were 45 less likely to develop dementia than their less active peers, though the level of physical activity did not seem to matter in this age group. Any intensity of exercise among those over 65 appeared to be beneficial for brain health.
The findings are “consistent with previous work showing that more moderate or vigorous physical activity in midlife is associated with reduced dementia risk,” the authors write. “While some studies report benefits of higher intensity physical activity in late-life, emerging evidence suggests that even light intensity physical activity is beneficial for cognitive health among older adults.”
Being physically active in young adulthood did not seem to affect dementia risk years down the road. although far fewer people in this age group ultimately developed dementia during the three plus decades of follow-up. Additional years of follow-up may be needed to better assess the effects of early-life exercise on late-life brain health.
The researchers also looked at whether participants carried the APOE-E4 gene variant, which increases the likelihood that someone will develop Alzheimer’s disease. They found that in midlife, higher physical activity did not affect dementia risk among those who carried APOE-E4. But in later life, exercise lowered dementia risk both in APOE-E4 carriers as well as noncarriers. The findings suggest that exercise later in life may be especially important for people who have a genetic predisposition to developing Alzheimer’s disease.
“This study builds on previous findings to support moderate or heavy midlife physical activity and any late-life physical activity as possible interventions for dementia risk reduction,” the authors note. Exercise increases blood flow throughout the body, including to the brain. Regular exercise also promotes the generation of new brain cells throughout life and reduces levels of body-wide inflammation. Increasingly, experts recognize inflammation as a driver for many chronic diseases of aging, including Alzheimer’s disease.
The bottom line: Keep moving, regardless of age. And the older you are, the more important it may be to stay physically active to help keep the brain young.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Francesca R. Marino, PhD; Chenglin Lyu, MS; Yuqing Li, MPH; et al: “Physical Activity Over the Adult Life Course and Risk of Dementia in the Framingham Heart Study.” JAMA Network Open, November 19, 2025
