Association of Long-term Ambient Ozone Exposure With Respiratory Morbidity in Smokers

Question What is the association of long-term ambient ozone exposure with health outcomes among individuals with a heavy smoking history and with or without airways obstruction? Findings In this cross-sectional study of 1874 current and former smokers with or without chronic obstructive pulmonary disease, higher concentration of 10-year historical ambient ozone exposure was associated with greater computed tomography scan-measured emphysema and gas trapping, worse patient-reported outcomes and functional status, and increased respiratory exacerbations. Meaning This study found that long-term ambient ozone exposure was associated with worse respiratory outcomes and increased emphysema and gas trapping, independent of smoking and workplace exposures, in smokers with or at risk for chronic obstructive pulmonary disease. Importance Few studies have investigated the association of long-term ambient ozone exposures with respiratory morbidity among individuals with a heavy smoking history. Objective To investigate the association of historical ozone exposure with risk of chronic obstructive pulmonary disease (COPD), computed tomography (CT) scan measures of respiratory disease, patient-reported outcomes, disease severity, and exacerbations in smokers with or at risk for COPD. Design, Setting, and Participants This multicenter cross-sectional study, conducted from November 1, 2010, to July 31, 2018, obtained data from the Air Pollution Study, an ancillary study of SPIROMICS (Subpopulations and Intermediate Outcome Measures in COPD Study). Data analyzed were from participants enrolled at 7 (New York City, New York; Baltimore, Maryland; Los Angeles, California; Ann Arbor, Michigan; San Francisco, California; Salt Lake City, Utah; and Winston-Salem, North Carolina) of the 12 SPIROMICS clinical sites. Included participants had historical ozone exposure data (n = 1874), were either current or former smokers (>= 20 pack-years), were with or without COPD, and were aged 40 to 80 years at baseline. Healthy persons with a smoking history of 1 or more pack-years were excluded from the present analysis. Exposures The 10-year mean historical ambient ozone concentration at participants' residences estimated by cohort-specific spatiotemporal modeling. Main Outcomes and Measures Spirometry-confirmed COPD, chronic bronchitis diagnosis, CT scan measures (emphysema, air trapping, and airway wall thickness), 6-minute walk test, modified Medical Research Council (mMRC) Dyspnea Scale, COPD Assessment Test (CAT), St. George's Respiratory Questionnaire (SGRQ), postbronchodilator forced expiratory volume in the first second of expiration (FEV1) % predicted, and self-report of exacerbations in the 12 months before SPIROMICS enrollment, adjusted for demographics, smoking, and job exposure. Results A total of 1874 SPIROMICS participants were analyzed (mean [SD] age, 64.5 [8.8] years; 1479 [78.9%] white; and 1013 [54.1%] male). In adjusted analysis, a 5-ppb (parts per billion) increase in ozone concentration was associated with a greater percentage of emphysema (beta = 0.94; 95% CI, 0.25-1.64; P = .007) and percentage of air trapping (beta = 1.60; 95% CI, 0.16-3.04; P = .03); worse scores for the mMRC Dyspnea Scale (beta = 0.10; 95% CI, 0.03-0.17; P = .008), CAT (beta = 0.65; 95% CI, 0.05-1.26; P = .04), and SGRQ (beta = 1.47; 95% CI, 0.01-2.93; P = .048); lower FEV1% predicted value (beta = -2.50; 95% CI, -4.42 to -0.59; P = .01); and higher odds of any exacerbation (odds ratio [OR], 1.37; 95% CI, 1.12-1.66; P = .002) and severe exacerbation (OR, 1.37; 95% CI, 1.07-1.76; P = .01). No association was found between historical ozone exposure and chronic bronchitis, COPD, airway wall thickness, or 6-minute walk test result. Conclusions and Relevance This study found that long-term historical ozone exposure was associated with reduced lung function, greater emphysema and air trapping on CT scan, worse patient-reported outcomes, and increased respiratory exacerbations for individuals with a history of heavy smoking. The association between ozone exposure and adverse respiratory outcomes suggests the need for continued reevaluation of ambient pollution standards that are designed to protect the most vulnerable members of the US population. This cohort study analyzes ozone exposure levels, smoking history, self-reported respiratory outcomes, and other demographic and clinical data of participants in the Air Pollution Study of the Subpopulations and Intermediate Outcome Measures In COPD Study.