Association between chronic obstructive pulmonary disease and long-term ozone and PM2.5 exposure among Medicare participants: a national cohort study

Abstract

BACKGROUND AND AIM: Chronic obstructive pulmonary disease (COPD) is the third leading cause of death globally and both ozone and PM2.5 exposures are main risk factors. However, few studies have investigated the association of long-term ambient ozone exposure with respiratory morbidity and its simultaneous effect with PM2.5. METHODS: A nationwide population-based open cohort study was used to estimate the association between long-term exposure to ambient ozone, PM2.5 and COPD incidence. The study population included all Medicare enrollees (aged ≥65 years) who were always enrolled in Medicare free-for-service program and in both Medicare Part A (hospital insurance) and Part B (medical insurance) in the contiguous United States from 2000-2016. We estimated the hazard ratios (HRs) for the first diagnosis with COPD using single- and co-pollutant Cox proportional hazards models that controlled for demographic characteristics, Medicaid eligibility, and area-level covariates. We further looked at this relationship at lower pollutant concentrations, restricting Medicare enrollees who were always exposed to pollutant levels below the US EPA National Ambient Air Quality Standards [NAAQS] (annual PM2.5 ≤12 μg/m³ and warm-season ozone ≤50 ppb), and among potentially susceptible subgroups. RESULTS:Among the full cohort of 18.9 million enrollees, increases of 10 ppb in annual warm-season ozone and 10 μg/m³ in annual PM2.5 were associated with increased risk of first diagnosis with COPD, with HRs of 1.048 (1.039-1.057) and 1.054 (95% CI, 1.036-1.072) in the co-pollutant model, respectively. When restricting analyses to the below EPA low-exposure sub-cohort (9.6-million enrollees), the corresponding HRs were 1.160 (1.142-1.178) for exposure to ozone and 1.109 (95% CI, 1.068-1.151) for exposure to PM2.5. CONCLUSIONS:Both long-term ozone and PM2.5 exposures were associated with increased risk of COPD incidence among the US elderly population, even at concentrations below the current NAAQS standards. KEYWORDS: Air pollution, Multi-pollution, Chronic obstructive pulmonary disease