Is there a time in our adult life when physical exercise can delay or prevent dementia? Yes and a review of Framingham Heart Study data suggests people with the highest levels of physical activity during midlife and late life had forty to forty-five percent lower risk of all-cause dementia compared with those with lowest levels of physical activity. The study, appearing in JAMA Network Open, did not show an association between dementia and physical activity during early adult life. The findings may help future efforts to lower risk of dementia by timing interventions in the most relevant stages of adult life. Similar findings were observed from physical exercise and risk of Alzheimer’s disease.