Quantitative and qualitative imaging in marijuana users and smokers

To evaluate the effect of marijuana use compared to cigarette smoking on imaging findings in the lungs.

By searching the electronic medical record, we identified patients who were marijuana users who never smoked; current smokers; and non-marijuana never smokers, who underwent chest CT in our healthcare system in 2019. We generated a random sample of 100 marijuana users as well as 100 each age- and sex-matched controls from the current smoker and never-smoker groups. Patients with extensive airspace disease on CT were excluded. Quantitative CT analysis was performed to measure total lung volume (TLV). A thoracic radiologist reviewed chest CTs in a blinded fashion for the presence of emphysema, centrilobular ground glass opacities, mosaic attenuation, bronchial wall thickening, and coronary calcification.

Our study included 285 participants, comprising 89 non-smokers, 97 smokers, and 99 marijuana users. Despite propensity score matching, the marijuana user group was slightly younger than the smokers and non-smokers (mean age 59 versus 62 and 64 years, respectively, p = 0.04), with similar sex distribution across all groups. TLV was higher in smokers than marijuana users and non-smokers (p<.01 for both). By visual analysis, 62 % of smokers had emphysema versus 4 % of marijuana users (p<.001). Additionally, centrilobular ground glass opacities were more prevalent in smokers (15 %) than in marijuana users (2 %) (p = 0.0008). No significant difference was noted in the occurrence of mosaic attenuation between smokers and marijuana users. In terms of coronary artery calcification, more smokers had moderate to severe coronary artery calcifications compared to marijuana users (43 % versus 25 %, p = 0.01).

While emphysema and hyperinflation were common in smokers, they were rare in marijuana users.