Experts have long believed that exercise could help protect against the development of dementia. However, although they had observed a general pattern of reduced risk, the studies on the subject had been small, and often conflicting, with little consensus on what type, frequency or intensity of exercise might be best.
“There’s no real clear prescription that we can provide for physical activity,” said Dr. Joel Salinas, an assistant professor of neurology at New York University’s Grossman School of Medicine who specializes in treating people with dementia
But three large long-term studies published in recent months have attempted to characterize the types, intensities and durations of physical activity that confer the most general protection against dementia. These studies, which followed thousands, and even hundreds of thousands, of people for years at a time, confirm that regular physical activity, in many forms, plays a substantial role in reducing the risk of developing dementia.
Vigorous exercise seems to be best, but even non-traditional exercise, such as doing housework, can offer significant benefit. And surprisingly, it’s just as effective at reducing risk in those with a family history of dementia.
Many forms of exercise can prevent dementia.
In the first study, published July 27 in the journal Neurology, researchers analyzed health information from 501,376 participants who did not have dementia in a British database called the UK Biobank to establish links between physical activity and risk to develop the disease.
One of the main advantages of this database was that it had “very rich data about the genetics” of the participants, said Dr. Huan Song, a researcher at West China Hospital of Sichuan University, who was one of the authors of the study. This included a risk profile of participants based on whether they had genetic variants known to be associated with dementia or whether they had immediate family members with the disease.
At the start of the study, participants filled out detailed questionnaires about their participation in physical activities, such as playing sports, climbing stairs or walking, and whether they regularly commuted to work or cycled. They were also asked about various lifestyle factors, including how often they completed household chores.
One of the main limitations of previous studies was that “the definition of physical activity is quite weak,” said Dr. Song. “Some use the full amount, and others only focus on one mode of activity.” The British questionnaires provided specificity about what activities participants engaged in on a regular basis.
Participants were followed for 11 years, during which 5,185 developed dementia. The study found that in participants who did regular, vigorous activities, such as playing sports or exercising, the risk of developing dementia was reduced by 35 percent. Surprisingly, people who reported regularly completing housework also experienced a significant benefit; they had a 21 percent lower risk.
“Some people work really hard when they’re doing housework,” said Dr. Sandra Weintraub, a neurologist at Northwestern University’s Feinberg School of Medicine, who was not associated with this study. “Maybe if you do three hours of housework, you’re just as good as if you did 30 minutes of aerobic exercise.”
For Dr. Salinas, who recommends that people aim for 150 minutes of moderate-to-vigorous intensity exercise per week, the results reinforce the idea that regular moderate-to-vigorous exercise can promote brain health. Cultivating this exercise habit “is likely to have a very profound synergistic effect,” he said. “You get a lot more bang for your buck in terms of helping promote your own health through physical activity.”
Perhaps most encouragingly, the association between physical activity and a reduced risk of dementia extended to participants who had a family history of dementia.
“It’s very important to know that if you have a family history of dementia, you can use physical activity to reduce your risk,” Dr Song said.
Start by doing what you love the most.
The second paper, published last week in Neurology, compiled 38 studies to see which leisure activities were associated with a reduced risk of dementia. In total, the studies followed more than two million participants without dementia for at least three years, during which 74,700 developed dementia.
After controlling for age, education and gender, the researchers found that participants who exercised regularly, defined as engaging in activities such as walking, running, swimming, dancing, playing sports or working out at the gym, had a 17 percent lower risk of suffering. develop dementia compared to those who do not.
This meta-analysis shows that dementia prevention is not limited to one activity, or even one type of activity. Given the diversity of physical activity the participants engaged in, “we recommend that people do whatever exercise they enjoy,” said Le Shi, a researcher at Peking University and one of the authors of the study
When it comes to reaping the benefits of physical activity, it’s never too early to start. In a third study published this month, researchers followed more than 1,200 children between the ages of 7 and 15 for more than 30 years. Those with higher levels of physical fitness as children had higher levels of cognitive functioning in middle age, suggesting that establishing a lifelong habit of physical activity could be beneficial for brain health.
Taken together, these studies suggest that the ways we move our bodies on a daily basis could increase over time. They also solidify the notion that regular, lifelong physical activity, in all its forms, goes a long way toward reducing the risk of dementia, even for people who are classified as high risk.
“Your brain is part of your body, and it will benefit from anything you do that’s good for your overall health,” Dr. Weintraub said.
Rachel Fairbank is a freelance science writer based in Texas.