Background: Limited data are available regarding marijuana smoking’s impact on development or progression of chronic obstructive pulmonary disease (COPD) in middle-aged or older adults with a variable history of tobacco cigarette smoking.

Methods: We divided ever-tobacco smoking participants in the Subpopulations and Intermediate Outcomes in COPD Study (SPIROMICS) into three groups based on self-reported marijuana use: current, former or never marijuana smokers (CMS, FMS or NMS, respectively). Longitudinal data were analyzed in participants with ≥2 visits over a period of ≥52 weeks.

Measurements: We compared CMS, FMS and NMS, and those with varying amounts of lifetime marijuana use. Mixed effects linear regression models were used to analyze changes in spirometry, symptoms, health status and radiographic metrics; zero-inflated negative binomial models were used for exacerbation rates. All models were adjusted for age, sex, race, baseline tobacco smoking amount, and FEV1 %predicted.

Results: Most participants were followed for ≥4 years. Annual rates of change in FEV1, incident COPD, respiratory symptoms, health status, radiographic extent of emphysema or air trapping, and total or severe exacerbations were not different between CMS or FMS versus NMS or between those with any lifetime amount of marijuana use versus NMS.

Conclusions: Among SPIROMICS participants with or without COPD, neither former nor current marijuana smoking of any lifetime amount was associated with evidence of COPD progression or its development. Because of our study’s limitations, these findings underscore the need for further studies to better understand longer term effects of marijuana smoking in COPD.