Ambient Air Pollution and COPD: The Multiethnic Cohort Study.

Abstract

Rationale: Globally, in 2019, chronic obstructive pulmonary disease (COPD) was the third leading cause of death. While tobacco smoking is the predominant risk factor, the role of long-term air pollution exposure in increasing risk of COPD remains unclear. Moreover, there are few studies that have been conducted in racial and ethnic minoritized and socioeconomically diverse populations, while accounting for smoking history and other known risk factors.

Objective: To evaluate the association for ambient air pollution and COPD in a multiethnic population in California.

Methods: Among 38,654 African American, Japanese American, Latino and White California participants in the Multiethnic Cohort study enrolled in the fee-for-service component of Medicare, we used Cox proportional hazards regression to estimate the association of time-varying ambient air pollutants: particulate matter with diameter ≤2.5 μm or 10 μm (PM_2.5, PM₁₀), nitrogen dioxide (NO₂), carbon monoxide (CO), ozone (O₃), benzene and ultrafine particles (UFP) with COPD risk (n=10,915 cases; 8.8 years of follow-up). Subgroup analyses were conducted by race and ethnicity, sex, smoking status at MEC baseline questionnaire, and neighborhood socioeconomic status (nSES).

Results: We observed positive associations for NOx (per 50 ppb) with risk of COPD (hazards ratios (HR)=1.45; 95% CI: 1.35-1.55). The associations for NO₂ (per 20 ppb), PM_2.5 (10ug/m3), PM₁₀ (10ug/m3), CO (1000 ppb), and UFP (IQR=5241.7 particles/cm3) with risk of COPD were in similar directions as these air pollutants are highly correlated with NOx. These associations were found in African American, Latino, and Japanese American participants, but not in whites (p-heterogeneity across race and ethnicity<0.04). These associations also differed by nSES with effects being stronger in racial and ethnic minoritized populations and residents of low SES neighborhoods.

Conclusion: Long-term ambient air pollutant exposure is associated with COPD risk in a multiethnic, older adult (>65 years of age), population.