Reduced ambient PM2.5, better lung function, and decreased risk of chronic obstructive pulmonary disease in adults: a longitudinal cohort study

Abstract

Background: Several studies reported that long-term exposure to fine particulate matter (PM2.5) was associated with an increased risk of chronic obstructive pulmonary disease (COPD). It remains unclear whether reduced PM2.5 can decrease the risk of COPD development. We conducted a longitudinal cohort study to investigate the associations of dynamic changes in long-term exposure to ambient PM2.5 with changes in lung function and the incidence of COPD. Methods: A total of 109,273 adults (aged 18 years or older) were recruited in Taiwan between 2001 and 2014. The change in PM2.5 (ΔPM2.5) was defined as the difference between the values measured during follow-up and during the immediately preceding visit. We used a multivariable linear mixed model and time-varying Cox model to investigate the effects of ΔPM2.5 on lung function and the incidence of COPD, respectively. Result: The PM2.5 concentration in Taiwan increased during 2002-2004 and began to decrease around 2005. Every 5-µg/m3 decrease in the PM2.5 (i.e., ΔPM2.5 of 5 µg/m3) was associated with an increase of 13.67 mL/year (95%CI: 11.96,15.36) in forced expiratory volume in 1 s (FEV1), 10.38 mL/year (95%CI: 8.42,12.33) in forced vital capacity (FVC), 35.06 mL/s/year (95%CI: 31.20,38.89) in maximum mid-expiratory flow (MMEF), 0.14%/year (95%CI: 0.01%, 0.17%) in FEV1/FVC/year, and a decrease of 11% (95%CI: 5%, 17%) in the risk of COPD development. The stratified and sensitivity analyses generally yielded similar results. Conclusion: An improvement in PM2.5 air quality is associated with a better level of FEV1, FVC, MMEF, and FEV1/FVC, and a decreased risk of COPD development.