Does fine particulate matter (PM 2.5 ) affect the benefits of habitual physical activity on lung function in adults: a longitudinal cohort study.

Background: Physical activity (PA) increases a person's inhalation of air pollutants due to greater ventilation, possibly leading to larger adverse health effects. This study aims to investigate the combined effects of long-term exposure to fine particulate matter (PM _2.5 ) and habitual PA on lung function in adults.
Methods: This was a longitudinal cohort study that included 278,065 Taiwan residents with an age of 20 years old or above who joined a standard medical screening programme between 2001 and 2014. Each participant received at least one medical examination (including spirometric, blood, and urinary tests and a standard self-administered questionnaire survey) during the study period. We estimated the 2-year average PM _2.5 concentrations at each participant's address using a new physical model based on observational data. Information on the participants' PA was collected using the standard self-administrated questionnaire. Generalised linear mixed models were used to investigate the combined effects of PM _2.5 and PA on pulmonary function. We also performed stratified analyses by different levels of PM _2.5 exposure and habitual PA.
Results: Each 10 MET-h increase in PA was associated with a higher level of 0.20%, 0.16%, and 0.19% in forced vital capacity (FVC), forced expiratory volume in the first second (FEV ₁ ), and maximum mid-expiratory flow (MMEF), respectively, after adjusting for PM _2.5 exposure and a wide range of covariates including age, sex education, body mass index, lifestyles, and health conditions. Each 10 μg/m ³ increase in PM _2.5 was associated with a lower FVC, FEV ₁ , and MMEF (2.43%, 2.78% and 3.10%, respectively). Negative interactions were observed, and PM _2.5 exposure was associated with a greater reduction in lung function among the participants with higher PA levels.
Conclusions: We found significant negative interaction effects between long-term exposure to PM _2.5 and habitual PA, suggesting that the increased intake of PM _2.5 due to PA may attenuate the benefits of habitual PA on lung function. However, the PA benefits generally remained stable at different stratum of PM _2.5 in the stratified analyses, and habitual PA may still be recommended to people residing in relatively polluted regions.