Physical Activity, Air Pollution, and Mortality: A Systematic Review and Meta-analysis.

Abstract

Background: As whether the positive effects of physical activity on mortality outweigh the negative effects of exposure to pollution is still under debate, we conducted a systematic review and meta-analysis on the risk of mortality for combined exposure to physical activity and air pollution.

Methods: PubMed, Cochrane, Embase and ScienceDirect databases were searched for studies assessing the risk of mortality for combined exposure to physical activity and air pollution.

Results: We included eight studies for a total of 1,417,945 individuals (mean 57.7 years old, 39% men) - 54,131 died. We confirmed that air pollution increased the risk of mortality by 36% (OR 1.36, 95CI 1.05-1.52), whereas physical activity in a non-polluted environment decreased the risk of mortality by 31% (OR 0.69, 95CI 0.42-0.95). Our meta-analysis demonstrated that combined exposure to physical activity and air pollution decreased the risk of mortality by 26% (OR 0.74, 95CI 0.63-0.85). This risk decreased whatever the level of physical activity: by 19% (OR 0.81, 95CI 0.69-0.93) for low, by 32% (OR 0.68, 95CI 0.44-0.93) for moderate, and by 30% (OR 0.70, 95CI 0.49-0.91) for high physical activity in air pollution.

Conclusion: We confirmed that air pollution increased mortality by 36% in our meta-analysis. Despite the controversial benefit-risk, we demonstrated a reduction of mortality by 26% for combined exposure to physical activity and air pollution - nearly comparable to the reduction of mortality when practicing physical activity without air pollution (- 31%). However, the limited number of included studies precluded the demonstration of a dose-response relationship between levels of physical activity and air pollution, and reduction of mortality.