Summary: Vigorous exercise appears to offer smaller benefits for certain brain health measures when it takes place in areas with higher air pollution.
Source: AAN
New research indicates that vigorous physical activity—such as running, fast cycling or competitive sports—may deliver fewer protective effects on some markers of brain health when performed in environments with elevated air pollution.
The study assessed two brain-imaging markers: white matter hyperintensities (WMH), which reflect small areas of injury in the brain’s white matter, and total gray matter volume. Larger gray matter volume and smaller WMH volumes are generally interpreted as indicators of healthier brain structure and reduced risk for cognitive decline.
Results of the analysis are published in the journal Neurology.
“Vigorous exercise can increase breathing rate and the volume of air inhaled, potentially raising exposure to airborne pollutants,” said study author Melissa Furlong, Ph.D., of the University of Arizona in Tucson. “Prior research has linked air pollution with adverse brain outcomes, so we examined whether pollution levels change the brain-related benefits of physical activity.”
The authors found that physical activity was associated with better brain measures in areas with relatively low air pollution. However, the protective association of vigorous physical activity with white matter health was substantially reduced in the locations with the highest measured pollution. Importantly, the overall effect of air pollution on the brain in this study was modest—comparable to about half the effect of one year of aging—whereas the benefits associated with vigorous activity were larger, roughly comparable to the difference seen with being three years younger.
Researchers analyzed data from about 8,600 UK Biobank participants with an average age of 56. Participants’ long-term exposure to common air pollutants—nitrogen dioxide (NO2) and fine particulate matter (PM)—was estimated using land use regression models. These models combine measurements from monitoring stations with information about local land use, vehicle traffic, and other pollution sources to estimate pollution levels at specific addresses.
Participants were grouped into four exposure categories, from lowest to highest air pollution. Each person also wore an accelerometer for one week to objectively record physical activity. Based on accelerometer data, researchers classified weekly vigorous physical activity into categories ranging from none to 30 minutes or more.
On average, people who did the most vigorous activity had about 800 cm3 of gray matter volume, compared with about 790 cm3 among those who reported no vigorous exercise. The analysis showed that pollution levels did not meaningfully change the relationship between physical activity and gray matter volume. By contrast, pollution did influence the relationship between vigorous activity and WMH: vigorous exercise was linked to lower WMH volume in areas with low pollution, but this association diminished in high-pollution areas.
After adjusting for age, sex and other potential confounders, the pattern remained: vigorous physical activity correlated with reduced white matter hyperintensities in cleaner-air areas, but similar benefits were not observed among people living in the most polluted areas.
The authors caution that this is observational research and cannot prove cause and effect. One limitation is that air pollution estimates were based on a single year, while pollution can vary over time. The researchers call for further studies to confirm these findings and to explore whether reducing pollution exposure during exercise—by choosing routes away from heavy traffic or exercising at times when pollution is lower—might preserve the brain benefits of vigorous activity.
If future research supports these results, public health measures could help maximize the cognitive benefits of exercise. Potential strategies include designing walking and cycling paths away from busy roads, providing local air-quality information to help people choose lower-exposure times and locations for outdoor exercise, and integrating pollution considerations into urban planning.
About this exercise and pollution research news
Author: M.A Rosko
Source: AAN
Contact: M.A Rosko – AAN
Image: The image is in the public domain
Original Research: The findings will appear in Neurology