Dirty air could cancel out some of the brain benefits of exercise, a new study suggests.
"Physical activity is associated with improved markers of brain health in areas with lower air pollution," said study author Melissa Furlong. "However, some beneficial effects essentially disappeared for vigorous physical activity in areas with the highest levels of air pollution." Furlong is an environmental epidemiologist at the University of Arizona in Tucson.
For the study, her team compared certain markers of brain health, including the amount of gray matter (more is healthier) and lesions in the brain's white matter, a sign of injury.
The researchers also assessed the activity levels of 8,600 people in the United Kingdom (average age, 56) and their exposure to air pollution, including nitrogen dioxide and particulate matter.
After adjusting for age, sex and other factors, the study found that vigorous exercise reduced white matter lesions among folks who exercised in areas with low air pollution, but not among those who got a vigorous workout in places with dirty air.
People who had the highest amounts of vigorous exercise had more gray matter than people who didn't do any vigorous exercise (800 cubic centimeters versus 790), the study found. And pollution exposures did not alter the effects of physical activity on gray matter volume.
The findings were published online Dec. 8 in the journal Neurology.
The study findings don't mean people should avoid exercise, Furlong noted.
"Overall, the effect of air pollution on brain health was modest -- roughly equivalent to half the effect of one year of aging, while the effects of vigorous activity on brain health were much larger -- approximately equivalent to being three years younger," she said in a journal news release.
While more study is needed, if the findings can be confirmed, public policy could be used to address exposure to air pollution during exercise, Furlong said.
"For example, since a significant amount of air pollution comes from traffic, promoting running or bicycling along paths far from heavy traffic may be more beneficial," she suggested.
Harvard Health has more on the brain benefits of exercise.
SOURCE: Neurology, news release, Dec. 8, 2021