Physical activity, air pollution may interact, affect brain health

Physical activity and air pollution correlated with positive and negative brain outcomes, respectively, according to study results published in Neurology.

These effects may interact, researchers noted.

“Evidence suggests that the combined effects of [air pollution] and [physical activity] may be biologically significant, particularly for the brain,” Melissa A. Furlong, PhD, of the department of community, environment and policy at the University of Arizona, and colleagues wrote. “Aerobic exercise in moderately polluted environments reduces serum levels of brain-derived neurotrophic factor (BDNF) in humans and reduces BDNF gene expression in rats. In humans, the benefits of [physical activity] on cardiopulmonary outcomes are attenuated in areas of high [air pollution], and [air pollution] may have stronger associations with respiratory health among persons with high levels of [physical activity].”

According to the investigators, epidemiological research has yet to examine this interaction on the brain. To address this research gap, they analyzed data from 8,600 adults (average age, 55.55 years) of the U.K. Biobank between 2006 and 2010. They used wrist accelerometers, multimodal MRI with T1 images,T2 FLAIR data and land use regression to examine vigorous physical activity, structural brain volumes and air pollution, respectively, among portions of the entire sample.

Furlong and colleagues corrected for multiple testing and found overall models showed a positive association between vigorous physical activity and grey matter volume (GMV) and a negative association between vigorous physical activity and white matter hyperintensity volume (WMHV). Nitrogen dioxide, PM_{2.5absorbance} and PM_2.5 negatively correlated with GMV. The researchers noted nitrogen dioxide and PM_{2.5absorbance} interacted with vigorous physical activity on WMHV. They reported stronger associations between air pollutants and WMHVs among individuals with high vigorous physical activity, as well as a negative association between vigorous physical activity and WMHV among individuals in areas of low nitrogen dioxide and PM_{2.5absorbance.}

“If these findings are replicated further, policy could be structured to minimize exposure to [air pollution] during exercise,” Furlong and colleagues wrote. “Since most [air pollution] sources are traffic-related, promoting running or bicycling along paths far from heavily trafficked roads may reduce [air pollution]-related risks. Additionally, risk assessment measures for [air pollution] should consider those with high [physical activity] as a subpopulation of possible concern.”