Long-term marijuana smoking linked to increased pulmonary disease in HIV-positive men

HIV-infected men who smoke marijuana for several years are at heightened risk of developing both infectious and non-infectious lung diseases, regardless of whether they also smoke tobacco products, researchers at Dana-Farber Cancer Institute report in a study published today in the new online journal EClinicalMedicine.

The findings suggest that healthcare providers can have an important role in reducing the risk of certain lung diseases in HIV-positive patients by counseling them about the potential harm of marijuana smoking on lung health, the study authors state. Such counseling can be particularly effective at a time when marijuana use is increasing in the United States, with 10 states and the District of Columbia having legalized recreational use of the drug.

“Studies have shown that marijuana smoking is at least two to four times more prevalent among HIV-positive men than the general population,” says Dana-Farber’s Dana Gabuzda, MD, the senior author of the paper. “It has been proposed that marijuana smoke is a potential risk factor for lung disease because it contains many of the same toxic chemicals as cigarette smoke. Previous studies that explored this question have produced inconsistent results. Our study is the largest investigation of smoked marijuana and risk of lung diseases in HIV-infected individuals to date.”

The study involved 2,704 men participating in the Multicenter AIDS Cohort Study, half of whom were HIV-positive and half of whom were not. Investigators gathered data on participants’ marijuana and tobacco smoking, and tabulated it with reports and records of pulmonary disease diagnoses among the patients.

The researchers found that, between 1996 and 2014, HIV-positive participants were 54 percent more likely to be diagnosed with an infectious pulmonary disease, and 20 percent more likely to be diagnosed with a non-infectious pulmonary disease, than HIV-negative participants were.

“We found that HIV-positive men who smoked marijuana for several years had a significantly increased risk of developing infectious lung diseases and chronic bronchitis, independently of whether they smoked tobacco or had other risk factors for lung disease,” Gabuzda remarks. “These risks increased even further if they smoked both tobacco and marijuana. By contrast, smoking marijuana was not associated with lung disease in HIV-uninfected men.”

Scientists have offered a variety of reasons why HIV infection may increase susceptibility to lung disease. These include depletion and dysfunction of immune system cells in the lungs; persistent activation of immune cells; chronic inflammation; an imbalance of microorganisms in the respiratory tract; and a decreased ability to neutralize unstable oxygen molecules known as free radicals.

The authors of the paper note that the study focused solely on smoked marijuana, not forms of the drug that have been infused into foods or liquids. “Our findings highlight the need or research on the relative risks and merits of non-smoked versus smoked marijuana for medicinal and other purposes,” Gabuzda remarks.

The lead author of the study is David R. Lorenz, PhD, of Dana-Farber. Co-authors are Hajime Uno, PhD, of Dana-Farber and Steven M. Wolinsky, MD, of Northwestern University.

The study was supported by the National Institutes of Health (grants R01 DA030985 and DA046203). The MACS cohort was funded by the National Institute of Allergy and Infectious Diseases with additional co-funding from the National Cancer Institute and National Institute on Drug Abuse.