Emphysema, airway inflammation more common among marijuana than tobacco smokers

Individuals who smoked marijuana were more likely to have emphysema, airway changes and gynecomastia than tobacco-only smokers and nonsmokers, according to a study published in Radiology.

“There is a public perception that marijuana is safe, safer than cigarettes, but this study raises concerns that this may not be true,” Luke Murtha, BMBS, FRCPC, of Ottawa Hospital in Canada, told Healio. “Ultimately, we need a more robust study before we can make sweeping conclusions.”

In a retrospective case-control study, Murtha and colleagues analyzed chest CT examinations of 56 marijuana smokers (34 men; mean age, 49 ± 14 years), 33 tobacco-only smokers (18 men; mean age, 60 ± 6 years) and 57 nonsmokers (32 men; mean age, 49 ± 14 years) from October 2005 to July 2020 to observe differences between rates of emphysema, airway changes, gynecomastia and coronary artery calcification among the smoking groups.

Researchers found that 42 (75%) marijuana smokers had emphysema, compared with three (5%; P < .001) nonsmokers and 22 (67%) tobacco-only smokers, although the latter comparison did not reach statistical significance. Marijuana smokers also had more instances of paraseptal emphysema, occurring in 27 (48%) individuals, whereas only three (5%; P < .001) nonsmokers and eight (24%; P = .03) tobacco smokers had this emphysema subtype.

According to researchers, marijuana smokers also had higher rates of airway inflammation in the form of bronchial thickening (64% vs. 11% nonsmokers; P < .001; vs. 42% tobacco-only; P = .04), bronchiectasis (23% vs. 4% nonsmokers; P = .002; vs. 6% tobacco-only; P = .04) and mucoid impaction (46% vs. 2% nonsmokers; P < .001 vs. 15% tobacco-only; P = .003).

Murtha told Healio these findings in marijuana smokers could mean the substance is harming the lungs more so than tobacco.

“These instances of large and small airway diseases found for marijuana users suggests that marijuana may have additional effects on the lungs above tobacco alone,” he said.

Chest CT examinations also showed that 13 out of 34 (38%) individuals who smoked marijuana had instances of gynecomastia, which was more than both nonsmokers (5 of 32; 16%; P = .039) and tobacco-only smokers (2 of 18; 11%; P = .04).

Because all tobacco smokers were aged older than 50 years, researchers also conducted additional age- and sex-matched subgroup analyses that included 30 marijuana smokers (23 men), 33 tobacco-only smokers (18 men) and 29 nonsmokers (17 men).

In this adjusted subgroup analysis, researchers found that 28 (93%) marijuana smokers had emphysema compared with 22 (67%) tobacco-only smokers (P = .009) and two (7%) nonsmoking controls (P < .001), showing a significantly higher emphysema rate among marijuana smokers.

Additionally, marijuana smokers had continued higher rates of bronchial thickening (83% vs. 42%; P < .001), bronchiectasis (33% vs. 6%; P = .006) and mucoid impaction (67% vs. 15%; P < .001) compared with tobacco-only smokers, with significant differences also seen between the marijuana and control groups.

When asked about the results of both analyses, Murtha told Healio they were surprising.

“I was surprised that results were still significant when we compared the nonage-matched groups because that includes younger patients who presumably have had less lifetime exposure to smoke,” he said.

However, age-matched analysis showed that rate of coronary artery calcification did not differ between marijuana (70%) and tobacco-only (85%) smokers, according to researchers.

When asked how future studies will be different, Murtha said several factors should be assessed.

“Larger studies with more patients are needed to confirm findings, and researchers also need to quantify marijuana use,” Murtha told Healio. “Researchers should ask the question: Does inhalation method make a difference (eg. bong, blunt, joint, pipe and vape)?

“Additionally, what is the dose effect relationship?” Murtha added. “Researchers should seek answers to how much/how often do you need to smoke and for how long before we see lung changes. Future studies should also look into what the effects are of smoking marijuana alone vs. smoking marijuana and tobacco together.”

For more information:

Luke Murtha, BMBS, FRCPC, can be reached at lwmurtha@student.ubc.ca.

Reference:

Emphysema more common in marijuana smokers than cigarette smokers. https://www.rsna.org/news/2022/november/Emphysema-In-Marijuana-Smokers. Published Nov. 15, 2022. Accessed Nov. 15, 2022.