Rates of emphysema are higher in marijuana smokers than in cigarette smokers

Rates of emphysema are higher in marijuana smokers than in cigarette smokers

Airway inflammation and emphysema are more common in marijuana smokers than cigarette smokers, according to a study published in Radiology, a journal of the Radiological Society of North America (RSNA). The researchers said the difference could be due to the way marijuana is smoked and the fact that marijuana smoke enters the lungs unfiltered.

Marijuana is one of the most commonly used psychoactive substances in the world and the most commonly smoked substance after tobacco. Its use has increased in recent years with the legalization of recreational marijuana in Canada and many states in the United States. Increasing use has created an urgent need for information about marijuana's effects on the lungs, which is currently lacking.

We know what cigarettes do to the lungs. There are well-researched and established findings of cigarette smoking on the lungs. Marijuana, which we know very little about.”

Giselle Revah, MD, study author, cardiothoracic radiologist and assistant professor, University of Ottawa in Ottawa, Canada

To find out more, Dr. Revah and colleagues compared the chest CT results of 56 marijuana smokers with those of 57 non-smokers and 33 pure tobacco smokers.

Three-quarters of marijuana smokers had emphysema, a lung disease that causes difficulty breathing, compared with 67% of smokers who only smoked tobacco. Only 5% of non-smokers had emphysema. Paraseptal emphysema, which damages the tiny ducts that connect to the air sacs in the lungs, was the predominant emphysema subtype in marijuana smokers compared to the group that smoked only tobacco.

Airway inflammation was also more common in marijuana smokers than in nonsmokers and tobacco smokers, as was gynecomastia, enlarged male breast tissue due to a hormone imbalance. Gynecomastia was found in 38% of marijuana smokers, compared to 11% of tobacco-only smokers and 16% of controls.

The researchers found similar results in age-matched subgroups, where rates of emphysema and airway inflammation were again higher among marijuana smokers than among tobacco-only smokers.

There was no difference in coronary artery calcification between age-matched marijuana and tobacco-only groups.

Dr. Revah said the results were surprising, especially considering that patients in the tobacco-only group had extensive smoking histories.

"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, more so than tobacco," she said. “Furthermore, our results were still significant when we compared the non-age-matched groups, including younger patients who smoked marijuana and presumably had less exposure to cigarette smoke.”

The reasons for the differences between the two groups are likely due to several factors. Marijuana is smoked unfiltered, Dr. Revah solid, while tobacco cigarettes are usually filtered. This causes smoking marijuana to introduce more particles into the respiratory tract.

Additionally, marijuana is inhaled with a longer breath hold and puff volume than tobacco smoke.

"It has been suggested that smoking a marijuana joint deposits four times more particles in the lungs than an average tobacco cigarette," said Dr. Revah. “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 result in trauma and changes to the peripheral airspace.

More research is needed, said Dr. Revah, with larger groups of people and more data about how much and how often people smoke. Future research could also examine the effects of different inhalation techniques, such as through a bong, joint, or pipe.

“It would be interesting to see if the inhalation method makes a difference,” said Dr. Revah.

Source:

Radiological Society of North America

Reference:

Murtha, L., et al. (2022) Chest CT results in marijuana smokers. Radiology. doi.org/10.1148/radiol.212611.

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