麻豆传媒

Emphysema and airway inflammation were more common among marijuana smokers compared with tobacco-only smokers, according to a small retrospective case-control study.

In sex- and age-matched analyses, marijuana smokers -- most of whom also smoked tobacco -- had significantly higher rates of emphysema compared with tobacco-only smokers (93% vs 67%, P=0.009), and higher rates of paraseptal emphysema as well (57% vs 24%, respectively, P=0.09), reported Luke Murtha, MD, of the Ottawa Hospital in Ontario, Canada, and colleagues.

Overall, emphysema was slightly more common in marijuana smokers in the unmatched analysis as well (75% vs 67%), though the difference here was not significant, they noted in .

Marijuana smokers also had significantly higher rates of bronchial thickening (83% vs 42%, P<0.001), bronchiectasis (33% vs 6%, P=0.006), and mucoid impaction (67% vs 15%, P<0.001) in the matched (shown here) and unmatched analyses.

"It was surprising for us to find that more patients who smoked marijuana actually had emphysema than these heavy smokers ... and more of them had airway inflammation than the cigarette smokers," co-author Giselle Revah, MD, also of the Ottawa Hospital, told 麻豆传媒.

She noted that because the larger group of tobacco-only smokers were both older than the marijuana smokers and heavy smokers, it was presumed that they would have more exposure to smoke and therefore more serious adverse events.

"There's this public perception that marijuana is safe, and a lot of people think that it's safer than cigarettes," Revah said. "And this study raises the concern that that may not be true."

In an , Jeffrey Galvin, MD, of the University of Maryland School of Medicine in Baltimore, and Teri Franks, MD, of the Joint Pathology Center in Silver Spring, Maryland, noted that "the presence of paraseptal emphysema, especially in young individuals, is a marker to the radiologist of increased strain in the lung and points to the potential use of marijuana or other inhaled drugs."

Revah explained that she and her colleagues wanted to learn how to identify a marijuana smoker from a CT image in the way that is done for heavy cigarette smokers. "I was surprised at how little information there was," she said. "And that's probably because it [marijuana] was illegal in Canada, and it's still illegal in many places in the United States, and no one could ethically study it."

Having this information could make it easier to identify symptoms that come with marijuana use as opposed to tobacco-only use, she added. Only previous had looked at a potential link between marijuana and emphysema via lung imaging, and couldn't establish a strong association.

The current study also supported the known association between marijuana smoking and gynecomastia (an increase in breast tissue in males), which was seen in 38% of marijuana smokers compared with 11% of tobacco-only smokers (P=0.04), as well as 16% of nonsmoking controls (P=0.039).

There was no difference in coronary artery calcification between age-matched marijuana smokers (70%) and tobacco-only smokers (85%; P=0.16).

"The patients in our ... group are very heavy smokers, so we're not comparing marijuana [use] to light smoking, we're comparing the group to heavy smokers," Revah noted. "But the question is, is it the marijuana alone or the synergistic effect between the marijuana and tobacco?"

She added that many questions remain about the effects of marijuana smoking, and she's currently working on a prospective study that fully separates marijuana-only users from tobacco-only users.

The authors hypothesized that higher rates of bronchial wall thickening and inflammation in marijuana users could be related to the use of filters on cigarettes. Longer inhalation times and keeping smoke in the mouth for longer could also be related to the higher rates of emphysema, but Revah emphasized that more research is needed.

This study included 56 marijuana smokers (mean age 49, 34 men), of whom 50 also smoked tobacco, and 33 tobacco-only smokers (mean age 60, 18 men) who were selected from a high-risk lung cancer screening program. The study also included 57 nonsmoking controls (mean age 49, 32 men).

Marijuana smokers who also smoked tobacco had an average smoking history of 25 pack-years, and the tobacco-only smokers had an average of 40 pack-years. The age- and sex-matched subgroups included 30 marijuana smokers, 33 tobacco-only smokers, and 23 controls.

Not surprisingly, higher rates of emphysema were seen among marijuana smokers compared with nonsmokers (75% vs 5%, P<0.001). Rates of bronchial thickening, bronchiectasis, and mucoid impaction were also significantly higher in the marijuana smokers versus nonsmokers.

Study limitations included the small sample sizes and the inability to quantify marijuana use -- only 28 of 56 marijuana smokers specified the amount, and users often share joints, inhale in different ways, and use different strains of marijuana, Murtha and team noted. There were also differences in lifetime duration of smoking, since the tobacco-only cohort came from a lung cancer screening study where everyone was over 50.

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