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With an estimated 57 million people worldwide having dementia and nearly triple that number expected by 2050, the authors “wanted to investigate whether the impact of physical activity on dementia risk differed or stayed consistent across the adult life course,” says Phillip Hwang, lead study author and assistant professor in the department of epidemiology at Boston University School of Public Health.
A downside of this study is that it can’t suggest how much exercise to do due to the measurement the researchers used, Hwang says.
It was “a composite measure based on the number of hours a person spends sleeping, in sedentary behaviour, and doing light, moderate and heavy activities in a day,” he added. “However, finding ways to be more active and moving around is important.”
Hwang’s findings are also affirmed by other studies that suggest more specific guidance.
A 2022 study found that people who walked just 3,800 steps per day lowered their risk of dementia by 25 percent, and, generally, the more steps participants walked, the greater the benefits were. Using a bike instead of a car , bus or train for transportation has been linked with a 19 percent lower risk of dementia and a 22 percent reduced risk of Alzheimer’s disease.
“Given what is already known about the benefits of physical activity on other conditions — such as the heart, mood, stress, etc., which are also related to the brain and cognition — there are lots of other reasons as well to be more active,” Hwang says.
Adults need at least 150 to 300 minutes of moderate aerobic activity or 75 to 150 minutes of vigorous aerobic exercise per week, according to the World Health Organisation.
Such exercise could be, for example, 150 minutes of brisk walking, 75 minutes of vigorous running or cycling, and strength training a couple of times per week, Singh says.
She is part of the team that developed the Brain Care Score , a 21-point assessment of how a person fares on physical, lifestyle, social and emotional factors that they can change to protect their brain health.
If you’re new to exercise, begin with slower or shorter workouts, then gradually increase intensity , said Dr Raphael Wald, a neuropsychologist with Marcus Neuroscience Institute at Baptist Health South Florida.
“Starting too aggressively can lead to orthopaedic injuries, which may then limit your ability to exercise at all,” Wald adds.
Build consistent habits that can help ensure you stay active daily, Wald said, such as walking for 20 minutes before work or taking a short movement break during lunch.
Tracking activity and dementia risk
The new study’s findings are based on 1,526 participants in early adult life — ages 26 to 44 — nearly 2,000 middle-aged adults, and nearly 900 (mostly white) older adults who were part of the long-term Framingham Heart Study .
Physical activity levels in early adult life weren’t associated with dementia risk in either direction, the authors found.
They also discovered that even for older adults who had the strongest genetic risk factor for Alzheimer’s disease — the APOE ε4 gene — high physical activity was still linked with a 66 percent lower risk of dementia.
The study has important limitations, according to the experts.
“People who are more active may also engage in other healthy behaviours, have better baseline health, or differ in ways the researchers couldn’t fully measure,” Singh says.
The team acknowledged that it didn’t have details on middle- and older-age adults’ physical activity levels in their early adult lives or how habits changed over time, which could also influence risk for dementia.
Participants may also misjudge their levels, so studies with tracker wearables would be a more objective way to measure exercise, Singh said.
Midlife and late life, possibly being extra critical for brain health, may be explained by a few factors, according to the experts.
“Exercise plays a major role in maintaining vascular health,” Wald says.
“The most common vascular risk factors — high blood pressure, type 2 diabetes, thyroid disease and high cholesterol — tend to emerge in midlife and later adulthood. It makes sense that exercise during these periods would have the greatest impact on reducing dementia risk.”
