A new study published in the journal Neurology has found that air pollution significantly reduces the benefits that outdoor physical activities such as jogging, cycling, or playing competitive sports usually have on the brain.
By investigating markers of brain disease like gray matter volumes and white matter hyperintensities, researchers led by the University of Arizona discovered that exercising in highly polluted areas can negatively impact brain health.
The scientists examined a cohort of 8,600 people with an average age of 56 from the UK Biobank and estimated their exposure to air pollution with land use regression, an algorithm measuring pollution levels, particularly in densely populated areas. Moreover, each person’s physical activity was measured for one week with a movement-detecting device called an accelerometer.
Participants who got the greatest amounts of vigorous physical activity each week had 800 cm3 gray matter volume, compared to an average of 790 cm3 gray matter volume in people who did not get any vigorous exercise, which shows an improved level of brain health. While pollution did not seem to alter the effects of exercise on gray matter volume, it nevertheless significantly increased white matter hyperintensity volumes, which is a marker of brain health decline.
“Vigorous exercise may increase exposure to air pollution and prior studies have shown adverse effects of air pollution on the brain,” said study lead author Melissa Furlong, an environmental epidemiologist at the University of Arizona. “We did show that physical activity is associated with improved markers of brain health in areas with lower air pollution. However, some beneficial effects essentially disappeared for vigorous physical activity in areas with the highest levels of air pollution.”
According to the scientists, public policy should take into account these findings in order to address people’s exposure to air pollution during exercise. For instance, since a significant amount of air pollution comes from traffic, promoting jogging or cycling along paths far from heavy traffic may prove beneficial.
“That’s not to say people should avoid exercise,” Furlong added. “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.”