Long-term exposure to particulate matter and COPD mortality: Insights from causal inference methods based on a large population cohort in southern China

Background: Evidence of the association between long-term exposure to particulate matter (PM) and chronic obstruc-tive pulmonary disease (COPD) mortality from large population-based cohort study is limited and often suffers from residual confounding issues with traditional statistical methods. We hereby assessed the casual relationship between long-term PM (PM2.5, PM10 and PM10-2.5) exposure and COPD mortality in a large cohort of Chinese adults using state-of-the-art causal inference approaches.Methods: A total of 580,757 participants in southern China were enrolled in a prospective cohort study from 2009 to 2015 and followed up until December 2020. Exposures to PM at each residential address were obtained from the Long-term Gap-free High-resolution Air Pollutant Concentration dataset. Marginal structural Cox models were used to investigate the association between COPD mortality and annual average exposure levels of PM exposure.Results: During an average follow-up of 8.0 years, 2250 COPD-related deaths occurred. Under a set of causal inference assumptions, the hazard ratio (HR) for COPD mortality was estimated to be 1.046 (95 % confidence interval: 1.034-1057), 1.037 (1.028-1.047), and 1.032 (1.006-1.058) for each 1-mu g/m3 increase in annual average concentra-tions of PM2.5, PM10, and PM10-2.5 respectively. Additionally, the detrimental effects appeared to be more pronounced among the elderly (age >= 65) and inactive participants. The effect estimates of PM2.5, PM10, and PM10-2.5 tend to be greater among participants who were generally exposed to PM10 concentrations below 70 mu g/m3 than that among the general population.Conclusion: Our results support causal links between long-term PM exposure and COPD mortality, highlighting the urgency for more effective strategies to reduce PM exposure, with particular attention on protecting potentially vulner-able groups.

Automated summary

Using state-of-the-art causal inference approaches, this large cohort study in southern China found a causal relationship between long-term exposure to particulate matter (PM) and chronic obstructive pulmonary disease (COPD) mortality. The detrimental effects were more pronounced among the elderly and inactive participants. Therefore, there is an urgent need for more effective strategies to reduce PM exposure and pay particular attention to vulnerable groups.