Impact of long-term exposure to ambient particulate matter and nitrogen dioxide on chronic obstructive pulmonary disease: results from the Women’s Health Initiative cohort

Rationale: Although COPD prevalence and exacerbations have been linked to ambient pollutants, evidence on the impact of ambient pollutants on COPD incidence is relatively sparse. Objectives: To evaluate the associations of long-term ambient particulate matter (PM_2.5; PM₁₀), nitrogen dioxide (NO₂), and incident self-reported COPD in the Women’s Health Initiative (WHI), a large prospective cohort study of post-menopausal women across the United States. Methods: We estimated annual average residential pollutant concentrations using validated spatiotemporal models and monitored data. We estimated pollutant-COPD associations as hazard ratios (HRs) and 95% confidence intervals (CI) per inter-quartile range (IQR) increase in pollutant using time-varying Cox proportional hazards models adjusted for potential confounders including sociodemographic characteristics, lifestyle and health factors, and WHI Clinical Center at baseline. Finally, we assessed the joint impact of exposure to multiple pollutants using quantile-based G-computation for survival outcomes. Measurements and Main Results: During the median follow-up time of 11.1 years, the study participants experienced 3532 cases of COPD. HRs ranged from 1.20 (95% CI:1.15, 1.26) per IQR increase in PM_2.5, to 1.19 (95% CI:1.13, 1.26) per IQR increase in NO₂, to 1.10 (95% CI:1.06, 1.15) per IQR increase in PM₁₀. In our multi-pollutant model, a quartile increase in PM_2.5 and NO₂ was associated with a HR of 1.16 (95% CI:1.11, 1.20). Conclusions: In this national cohort of post-menopausal women, the long-term residential concentrations of ambient particulate matter (PM_2.5 and PM₁₀), and NO₂ were associated with a higher risk of incident COPD.