Emphysema more common in marijuana smokers than in cigarette smokers
Airway inflammation and emphysema are more common in marijuana smokers than in cigarette smokers, according to new research. The researchers said the difference may be due to the way marijuana is smoked and the fact that marijuana smoke enters the lungs unfiltered. The research study was published Nov. 15 in Radiology, a 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 significantly 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. “It has been suggested that smoking a joint of marijuana deposits four times more particles in the lung than an average tobacco cigarette.” — Giselle Reva, 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-researched and established findings of cigarette smoking on the lungs. The marijuana we know so little about.” To learn more, Dr. Revah and colleagues compared chest CT results from 56 marijuana smokers with those of 57 nonsmoking 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 had emphysema. Paraseptic emphysema, which destroys the tiny ducts connected to the air sacs in the lungs, was the predominant subtype of emphysema in marijuana smokers compared to the tobacco-only group. Airway changes in a 66-year-old male marijuana and tobacco smoker. Contrast-enhanced (A) CT and (B) coronal CT images show cylindrical bronchiectasis and bronchial wall thickening (arrowheads) in multiple lung lobes bilaterally in a background of paradiaphragmatic (arrows) and centripetal emphysema. Credit: Radiological Society of North America Airway inflammation was also more common in marijuana smokers than non-smokers and tobacco-only smokers. The same was true of gynecomastia, a condition of enlarged male breast tissue due to hormonal imbalance. Gynecomastia was found in 38% of marijuana smokers, compared to just 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 in marijuana smokers than tobacco-only smokers. There was no difference in coronary artery calcification between the age-matched marijuana and tobacco-only groups. According to Dr. Revah, the results were surprising, especially considering that the patients in the tobacco-only group had an extensive history of smoking. Pulmonary emphysema in (A, B) marijuana and (C, D) tobacco smokers. (A) Axial and (B) coronal CT images in a 44-year-old male marijuana smoker show paradiaphragmatic emphysema (arrowheads) in bilateral upper lobes. (C) Axial and (D) coronal CT images in a 66-year-old female smoker with centrilobular emphysema represented by areas of centrilobular lucency (arrowheads). Credit: Radiological Society of North America “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 over and above tobacco,” he said. “Furthermore, our results were still significant when we compared age-unmatched groups, including younger patients who smoked marijuana and who likely 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 probably several factors that contribute to the differences between the two groups. Marijuana is smoked unfiltered, Dr. Revah noted, while tobacco cigarettes are usually filtered. This results in more particles reaching the airways from smoking marijuana. In addition, marijuana is inhaled with a greater breath and inhalation volume than cigarette smoke. “It has been suggested that smoking a joint of marijuana deposits four times more particles in the lung than an average tobacco cigarette,” said Dr. Revah. “These particles are likely airway irritants.” The higher incidence of emphysema may also be due to the way marijuana is smoked. Full inhalation with a prolonged Valsalva maneuver, an attempt to exhale in a closed airway, can result in trauma and changes in the peripheral airspace. 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 inhalation techniques, such as through a bong, joint or pipe. “It would be interesting to see if the method of inhalation makes a difference,” said Dr. Revah. For more on this research, see Emphysema more common in marijuana smokers than cigarette smokers. Citation: “Breast CT Findings in Marijuana Smokers” by Luke Murtha, Paul Sathiadoss, Jean-Paul Salameh, Matthew DF Mcinnes and Giselle Revah, 15 Nov 2022, Radiology.DOI: 10.1148/radiol.212611
