The findings show only an association, and do not establish that physical activity directly prevents Alzheimer’s. That said, Buchman and his colleagues assessed the participants’ cognitive health and prior physical activity in detail at the start of the study, which allowed the researchers to all but rule out the possibility that undiagnosed or early-stage dementia was leading to low physical activity, says Michal Schnaider Beeri, PhD, an associate professor of psychiatry at the Mount Sinai School of Medicine, in New York City.
The big picture provided by actigraphs is the study’s main selling point, but it also leaves some questions unanswered. Because actigraphs don’t differentiate between the type or intensity of activity, it’s difficult to determine whether some types of physical activity protect against Alzheimer’s more than others.
The physical activity in the study “was for the most part heavily weighted toward non-exercise activity,” Buchman says. This non-exercise activity appears to be beneficial, but the study findings suggest that exercise might be even better.
Buchman and his colleagues tried to estimate the intensity of the participants’ activity by looking at whether their movements were spread out evenly throughout the day or clustered in short bursts suggestive of vigorous exercise. By this measure, the people whose physical activity was least intense were nearly three times more likely to develop Alzheimer’s compared to those whose activity was most intense.
In general, the evidence to date suggests that more vigorous activity appears to be better when it comes to staving off Alzheimer’s, says Richard S. Isaacson, M.D., an associate professor of clinical neurology at the University of Miami Miller School of Medicine.
“Do the exercise—push it,” Isaacson says. “This is one part of the puzzle.”