Emphysema is more common in marijuana smokers than in cigarette smokers
According to new research, airway inflammation and emphysema are more common in marijuana smokers than in cigarette smokers. Investigators said the difference could be due to the way the marijuana is smoked and the fact that marijuana smoke enters the lungs unfiltered. The study was published on November 15 in Radiologya journal of the Radiological Society of North America (RSNA).
Marijuana is the most commonly smoked substance after tobacco and one of the most widely used psychoactive substances in the world. Amid the legalization of recreational marijuana in Canada and many US states, its use has increased dramatically in recent years. With increasing use, there is an urgent need for information on the effects of marijuana on the lungs, which is currently lacking.
“Smoking a joint of marijuana has been suggested to deposit four times more particles in the lungs than an average tobacco cigarette.” — Giselle Revah, MD
“We know what cigarettes do to the lungs,” said study author Giselle Revah, MD, a cardiothoracic radiologist and assistant professor at the University of Ottawa in Ottawa, Canada. “There are well-documented and established findings about smoking on the lungs. We know very little about marijuana.
To find out more, Dr. Revah and his colleagues compared the chest CT results of 56 marijuana smokers with those of 57 non-smoking controls and 33 tobacco-only smokers.
Three-quarters of marijuana smokers had emphysema, a lung disease that causes difficulty breathing, compared to 67% of tobacco-only smokers. Only 5% of non-smokers suffered from emphysema. Paraseptal emphysema, which damages the tiny ducts that connect to air sacs in the lungs, was the predominant emphysema subtype in marijuana smokers compared to the tobacco-only group.
Airway inflammation was also more common in marijuana smokers than in non-smokers and tobacco-only smokers. The same was true for gynecomastia, a condition of enlarged male breast tissue due to hormonal imbalance. Gynecomastia was found in 38% of marijuana smokers, compared to only 11% of tobacco-only smokers and 16% of controls.
The researchers found similar results among age-matched subgroups, where rates of emphysema and airway inflammation were again higher among marijuana smokers than tobacco-only smokers.
There was no difference in coronary artery calcification between age-matched marijuana and tobacco-only groups.
According to Dr. Revah, the results were surprising, especially considering that the patients in the smoking group had long histories of smoking.
“The fact that our marijuana smokers – some of whom also smoked tobacco – had additional findings of airway inflammation/chronic bronchitis suggests that marijuana has additional synergistic effects on the lungs above tobacco,” said she declared. “Furthermore, our results were still significant when we compared age-unmatched groups, including younger patients who smoked marijuana and who had presumably had less lifetime exposure to cigarette smoke. .”
According to the CDC, 48.2 million people, or about 18% of Americans, used marijuana at least once in 2019.
There are likely several factors that contribute to the differences between the two groups. Marijuana is smoked unfiltered, Dr. Revah noted, while tobacco cigarettes are typically filtered. This results in more particles reaching the airways while smoking marijuana.
Additionally, marijuana is inhaled with a longer breath and volume of puffs than tobacco smoke.
“Smoking a marijuana joint has been suggested to deposit four times more particles in the lungs than an average tobacco cigarette,” Dr. Revah said. “These particles are likely respiratory irritants.”
The higher incidence of emphysema may also be due to the way marijuana is smoked. Full inhalation with a sustained Valsalva maneuver, an attempt to exhale against a closed airway, can lead to trauma and peripheral airspace changes.
More research is needed, Dr Revah said, with larger groups of people and more data on how much and how often people smoke. Future research could also examine the impact of different inhaling techniques, such as through a bong, joint or pipe.
“It would be interesting to see if the inhalation method makes a difference,” Dr. Revah said.
For more on this research, see Emphysema more common in marijuana smokers than cigarette smokers.
Reference: “Chest CT Findings in Marijuana Smokers” by Luke Murtha, Paul Sathiadoss, Jean-Paul Salameh, Matthew DF Mcinnes and Giselle Revah, November 15, 2022, Radiology.
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