Lifetime cannabis exposure and small airway function in a population-based cohort study

Background and objective The long-term effects of cannabis on small airway function remain unclear. We investigated associations between cannabis use and small airway function in a general population sample.

Methods Cannabis use was ascertained at multiple ages from age 18 to 45 years and quantified as joint-years among 895 participants in the Dunedin Multidisciplinary Health and Development Study. Small airway function at ages 38 and 45 years was measured using impulse oscillometry before and after inhalation of salbutamol. Analyses used multiple linear regression adjusting for tobacco use, body mass index, and height. Longitudinal analyses of cannabis use between 38 and 45 years also adjusted for IOS at age 38.

Results Lifetime cannabis joint-years with IOS differed between men and women: in women, cannabis use was associated with pre-bronchodilator R5, R20, X5, AX, and Fres and marginally associated with R5-R20. Cannabis use was not statistically significantly associated with any of the pre-bronchodilator IOS measures in men. Cannabis use between ages 38 and 45 was associated with a similar pattern of changes in IOS measures. After salbutamol, cannabis use was only statistically significantly associated with R5 and R20 among women and none of the IOS measures among men.

Conclusions Cannabis use is associated with small airway dysfunction at age 45 years, indicating an increase in peripheral airway resistance and reactance. These associations were greater and only statistically significant among women. Associations were weaker and mostly non-significant after bronchodilator use suggesting that cannabis-induced changes in small airways may be at least partially reversible.