The effects of marijuana smoking on lung function in older people

Background Previous studies have associated marijuana exposure with increased respiratory symptoms and chronic bronchitis among long-term cannabis smokers.The long-term effects of smoked marijuana on lung function remain unclear. Methods We determined the association of marijuana smoking with the risk of spirometrically-defined COPD [post-bronchodilator FEV1/FVC 20 pack-years and >20 joint-years, respectively. Results Approximately 20% of participants had been or were current marijuana smokers with most also having smoked tobacco cigarettes (83%). Among heavy marijuana users, the risk of COPD was significantly increased (adjusted odds ratio, aOR, 2.45; 95% CI, 1.55–3.88). Compared to never-smokers of marijuana and tobacco, heavy marijuana smokers and heavy tobacco smokers experienced a faster decline in FEV1 by 29·5 mL·year−1 (p=0·0007) and 21·1 mL·year−1 (p Interpretation Heavry marijuana smoking increases the risk of COPD and accelerates FEV1 decline in concomitant tobacco smokers beyond that observed with tobacco alone.