TORONTO—Regular physical activity is known to improve cognitive ability and help stave off dementia, and now Canadian researchers think they know why.
In a small study of post-menopausal women aged 50-90, researchers at the University of Calgary found those who were aerobically fit had improved blood flow to the brain and that, in turn, was linked with better cognitive function.

“Being sedentary is now considered a risk factor for stroke and dementia,” said principal investigator Marc Poulin, a physiologist at the University of Calgary.
“This study proves for the first time that people who are fit have better blood flow to their brain,” he added. “Our findings also show that better blood flow translates into improved cognition.”
The study involved 42 women who were divided into active and sedentary groups based on their fitness levels. In part, fitness levels were determined by questionnaires that asked about leisure, household, and volunteer activities and their frequency.
“They were doing everything from walking to swimming to dancing to cross-country skiing and hiking,” Poulin said of those in the physically fit group.
Surprisingly, the older women often were more active than their younger counterparts.
To conduct the study, researchers tested the women for oxygen uptake as they exercised on a stationary bike. On a subsequent day, their blood vessel capacity was measured by having them breathe elevated levels of carbon dioxide while at rest.
“This is where we assess the capacity of the blood vessels in the brain to respond to increased demand,” Poulin said yesterday from Calgary.
In the same way that a person’s heart function is measured using a treadmill stress test, “our idea was to use two tests to give us a sense of the capacity of the brain from a pure physiological level—so . . . how the blood vessels work,” Poulin said.
On another day, the researchers gave participants a battery of cognitive tests that assessed memory, speed of thinking, and the ability to multi-task and problem-solve.
They found that compared to women in the sedentary group, the active group had lower (10 percent) resting and exercising arterial blood pressure, higher (five percent) vascular responses in the brain during low-intensity exercise and when carbon dioxide blood levels were raised, and higher (10 percent) cognitive function scores.
“Essentially, the study provides new evidence to support the idea that beneficial effects of physical fitness on cognition are mediated, at least in part, at the vascular level,” said Poulin, noting the findings could have important implications for helping to prevent dementia in Canada’s aging population.
“There’s always the question that comes up: Does this mean you’re going to live longer? And there’s not a lot of evidence to suggest that this will extend one’s life,” he said.
“But one way to look at it is that it certainly adds more life to your years,” he stressed.