Physical fitness linked to lower risk of developing dementia

A study of over 650,000 US veterans found that those who scored highest on a treadmill test had less risk of dementia in 8.8 years of follow-up

By Jason Arunn Murugesu

Being physically fit lowers your risk of developing dementia, according to one of the largest studies to test this idea so far.

Edward Zamrini at George Washington University in Washington, DC and his colleagues studied the link between cardiovascular fitness and dementia in over 650,000 people who had previously served in the US military.

Several studies have already found that the fitter you are, the less likely you are to develop dementia, but Zamrini says these studies had small sample sizes and have not followed up their participants for long enough.

“Our study is different,” he says. “The cohort is large, free of dementia symptoms at baseline and has a long follow-up.”

The participants in this study had an average age of 61 at the start of the study and were followed up for an average of 8.8 years. In this time, 44,105 of them were diagnosed with dementia.

They were split into five equal-sized groups according to their performance in a treadmill test, which measures how much oxygen they used during exercise.

The team found that a person in the least-fit group would reduce their risk of developing dementia by 13 per cent if they moved into the second-least-fit group. If they moved into the fittest group, their risk of developing dementia dropped by 33 per cent.

Most of the participants were male, but a statistical test on the results from the 36,000 female participants showed no difference between the sexes.

However, the results may have been affected by the fact that the participants were veterans. People in this group are more likely to have post-traumatic stress disorder or a traumatic brain injury, which can exacerbate dementia symptoms.

The study only included people who did not show any explicit dementia symptoms at the outset. But some people with dementia have no symptoms early on in their condition, and so some participants may have started developing dementia before they took part in the study.

There might be several ways that increased fitness can protect against dementia, Zamrini says, such as improving blood flow to the brain and increasing connectivity between neurons. “It also leads to a lower risk of anxiety, depression, and other chronic disease risk factors,” he says.

Zamrini will present the results at the American Academy of Neurology’s annual meeting in Seattle in April. Next, the team plans to look for biomarkers that can link cardiovascular fitness to the risk of developing dementia.

“This work has a clear demonstration of a stepwise effect of aerobic fitness on risk for dementia,” says Ozioma Okonkwo at the University of Wisconsin-Madison. Exercise may stimulate the production of the a protein called BDNF, which is critical for our ability to learn and remember information, he says.