Pneumothorax risk factors in smokers with and without chronic obstructive pulmonary disease

Rationale: The demographic, physiological, and computed tomography (CT) features associated with pneumothorax in smokers with and without chronic obstructive pulmonary disease (COPD) are not clearly defined.

Objectives: We evaluated the hypothesis that pneumothorax in smokers is associated with male sex, tall and thin stature, airflow obstruction, and increased total and subpleural emphysema.

Methods: The study included smokers with and without COPD from the COPDGene Study, with quantitative chest CT analysis. Pleural-based emphysema was assessed on the basis of local histogram measures of emphysema. Pneumothorax history was defined by subject self-report.

Measurements and main results: Pneumothorax was reported in 286 (3.2%) of 9,062 participants. In all participants, risk of prior pneumothorax was significantly higher in men (odds ratio [OR], 1.55; 95% confidence interval [CI], 1.08-2.22) and non-Hispanic white subjects (OR, 1.90; 95% CI, 1.34-2.69). Risk of prior pneumothorax was associated with increased percent CT emphysema in all participants and participants with COPD (OR, 1.04 for each 1% increase in emphysema; 95% CI, 1.03-1.06). Increased pleural-based emphysema was independently associated with risk of past pneumothorax in all participants (OR, 1.05 for each 1% increase; 95% CI, 1.01-1.10). In smokers with normal spirometry, risk of past pneumothorax was associated with non-Hispanic white race and lifetime smoking intensity (OR, 1.20 for every 10 pack-years; 95% CI, 1.09-1.33).

Conclusions: Among smokers, pneumothorax is associated with male sex, non-Hispanic white race, and increased percentage of total and subpleural CT emphysema. Pneumothorax was not independently associated with height or lung function, even in participants with COPD. Clinical trial registered with www.clinicaltrials.gov (NCT00608764).