Quantitative computed tomography assessment of pulmonary structure in cannabis smokers

Rationale: Cannabis use has been on the rise in countries where use is legalized, but little is known about the pathological changes that occur in the lungs of cannabis users. We hypothesize that cannabis use in concomitant tobacco smokers is associated with alveoli destruction, airway inflammation and pulmonary vessel pruning as measured using computed tomography (CT) imaging, independent of tobacco smoking. Method and Materials: Participants from the Canadian cohort obstructive lung disease study were investigated. Cannabis smoking history was defined as the number of joints smoked per day multiplied by the number of years smoked (joint-years). CT images were acquired at full-inspiration and measurements included: low-attenuation-area under -950 HU (LAA₉₅₀), airway wall thickness (AWT), and pulmonary blood volume in vessels with a cross-section area below 5mm² (BV5) (VIDA Diagnostics). A multivariate ridge regression was used to assess the association for joint-years with LAA₉₅₀, AWT, and BV5 adjusted by covariates (age, sex, BMI, CT model, tobacco pack-years, smoking status and years of education). The model with BV5 was also adjusted by total blood vessel volume. Results: A total of 364 cannabis and tobacco smokers were investigated. The smokers had a mean age of 59±7yrs, mean pack-years and joint-years was 31±22 and 14±24, respectively, and 74% were male; mean FEV₁ and FEV₁/FVC were 87±20%_pred and 68±11%, respectively. Joint-years was associated with CT LAA₉₅₀ (p<0.0001), AWT (p=0.001) and TBV (p=0.003) measurements, independent of tobacco pack-years. Conclusion: Cannabis use is associated with CT measures reflecting emphysema, airway inflammation and vascular pruning, independent of tobacco use.