Will benefits of physical activity in reducing the risk of all-cause and cause-specific mortality be attenuated by exposure to air pollutant mixture? A prospective study in the UK Biobank

Abstract

Background

To explore whether benefits of physical activity (PA) in reducing all-cause and cause-specific [all-cancer, cardiovascular disease (CVD) and respiratory disease] mortality risk might be attenuated by air pollution from the perspective of pollutant mixture.

Methods

We included 381,454 participants from the UK Biobank. Self-reported information on PA was grouped according to guidelines in International Physical Activity Questionnaire. Air pollutant mixture (NO₂, NO_x, PM_2.5, PM₁₀, and PM_2.5-10) was estimated using a Land Use Regression model and converted into a joint air pollution score. Cox proportional-hazard models were used to examine their associations with death outcomes.

Results

During a median follow-up of 11.99 years, deaths due to all-cause, all-cancer, CVD, respiratory disease were 24,264, 12,602, 4903, and 1680, respectively. Per PA-level increment was associated with lower risk of all-cause, all-cancer, CVD, and respiratory disease death, with hazard ratios of 0.86 (0.84–0.87), 0.91 (0.89–0.93), 0.86 (0.82–0.89) and 0.70 (0.66–0.75), respectively. However, an interquartile increment in air pollutant mixture was associated with higher risk of the above death outcomes. Notably, PA's effect on decreasing mortality risk remained relatively robust across all strata of air pollutant mixture. The combination of high PA and lowest air pollutant mixture reduced mortality risk by 37%, 24%, 41% and 64% from all-cause, all-cancer, CVD, and respiratory disease, respectively.

Conclusions

At all levels of air pollutant mixture, PA was inversely related with mortality risk. PA might still be an appropriate strategy to lower all-cause and cause-specific mortality risk, even for individuals exposed to high-level air pollution in the UK.