Marijuana and chronic obstructive lung disease: a population-based study.
BACKGROUND
Our aim was to determine the combined and independent effects of tobacco and marijuana smoking on respiratory symptoms and chronic obstructive pulmonary disease (COPD) in the general population.


METHODS
We surveyed a random sample of 878 people aged 40 years or older living in Vancouver, Canada, about their respiratory history and their history of tobacco and marijuana smoking. We performed spirometric testing before and after administration of 200 microg of salbutamol. We examined the association between tobacco and marijuana smoking and COPD.


RESULTS
The prevalence of a history of smoking in this sample was 45.5% (95% confidence interval [CI] 42.2%-48.8%) for marijuana use and 53.1% (95% CI 49.8%-56.4%) for tobacco use. The prevalence of current smoking (in the past 12 months) was 14% for marijuana use and 14% for tobacco use. Compared with nonsmokers, participants who reported smoking only tobacco, but not those who reported smoking only marijuana, experienced more frequent respiratory symptoms (odds ratio [OR] 1.50, 95% CI 1.05-2.14) and were more likely to have COPD (OR 2.74, 95% CI 1.66-4.52). Concurrent use of marijuana and tobacco was associated with increased risk (adjusted for age, asthma and comorbidities) of respiratory symptoms (OR 2.39, 95% CI 1.58-3.62) and COPD (OR 2.90, 95% CI 1.53-5.51) if the lifetime dose of marijuana exceeded 50 marijuana cigarettes. The risks of respiratory symptoms and of COPD were related to a synergistic interaction between marijuana and tobacco.


CONCLUSIONS
Smoking both tobacco and marijuana synergistically increased the risk of respiratory symptoms and COPD. Smoking only marijuana was not associated with an increased risk of respiratory symptoms or COPD.
iCapture Centre for Cardiovascular and Pulmonary Research, St. Paul's Hospital and the University of British Columbia, Vancouver, Canada. wtan@mrl.ubc.ca
Wan C
WC
Tan
Christine
C
Lo
Aimee
A
Jong
Li
L
Xing
Mark J
MJ
Fitzgerald
William M
WM
Vollmer
Sonia A
SA
Buist
Don D
DD
Sin
D000328:Adult; D017677:Age Distribution; D000368:Aged; D001955:British Columbia / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D002189:Marijuana Abuse / Q000150:complications; D008385:Marijuana Smoking / Q000009:adverse effects*; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D011336:Probability; D011379:Prognosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D012720:Severity of Illness Index; D017678:Sex Distribution; D012907:Smoking / Q000009:adverse effects*; D013147:Spirometry; D011795:Surveys and Questionnaires; D015996:Survival Rate