Long-term marijuana smoking was associated with lung disease in HIV-infected (HIV+) but not HIV uninfected (HIV–) men who have sex with men (MSM), according to the results of a large, prospective cohort study.

Man smoking a marijuana cigarette Scott Harms/iStockphoto

“There were no significant interactions between marijuana and tobacco smoking in any multivariable model tested for HIV+ participants, indicating independent effects of these factors,” wrote David R. Lorenz, PhD, of the Dana-Farber Cancer Institute, Boston, and his colleagues.

These findings are especially important given that the proportion of HIV+ individuals who frequently smoke marijuana is higher than in the general population in the United States, and has increased in recent years, according to the report, published online in EClinicalMedicine.

The study examined 2,704 MSM who met eligibility criteria (1,352 HIV+ and 1,352 HIV− individuals), with a median age of 44 years at baseline and a median follow-up of 10.5 years. A total of 27% of HIV+ participants reported daily or weekly marijuana smoking for 1 year or more during follow-up, compared with 18% of the HIV− participants.

HIV+ participants who smoked marijuana were more likely to report one or more pulmonary diagnoses, versus nonsmoking HIV+ individuals during follow-up (41.0% vs. 30.0% infectious, and 24.8% vs. 19.0% noninfectious), according to the authors. In contrast, there was no association between marijuana smoking and either an infectious or noninfectious pulmonary diagnosis among HIV− participants (24.2% vs. 20.9%, and 14.8% vs. 17.7%, respectively).

For HIV+ individuals, each 10 days/month increase in marijuana smoking in the prior 2-year period was found to be associated with a 6% increased risk of infectious pulmonary diagnosis (hazard risk 1.06 [95% confidence interval 1.00-1.11]; P = .041). Overall, they found that from the 53,000 person-visits in the study, marijuana smoking was associated with increased risk of both infectious and noninfectious pulmonary diagnoses among the 1,352 HIV-infected participants independent of CD4 count, antiretroviral therapy (ART) adherence, and demographic factors as well.

In particular, viral suppression did not seem to interfere with this association between marijuana smoking and infectious pulmonary diagnoses, as it remained significant in models restricted to those person-visits with suppressed HIV viral load (HR 1.41 [1.03-1.91], P = .029).

The authors suggested that HIV-specific factors such as lung immune cell depletion and dysfunction, persistent immune cell activation, systemic inflammation, respiratory microbiome alterations, and oxidative stress, or a combination of these effects, may interact with the alveolar macrophage dysfunction seen in both humans and mouse models exposed to marijuana smoke. Thus, “a potential additive risk of marijuana smoking and HIV disease may explain the increased prevalence of infectious pulmonary diagnoses in our adjusted analyses,” Dr. Lorenz and his colleagues stated.

“These findings suggest that marijuana smoking is a modifiable risk factor that healthcare providers should consider when seeking to prevent or treat lung disease in people infected with HIV, particularly those with other known risk factors including heavy tobacco smoking, and low CD4 T cell count or advanced HIV disease,” they concluded.

The National Institutes of Health funded the study. The authors reported that they had no relevant disclosures.

SOURCE: Lorenz DR et al. EClinicalMedicine. 2019 Jan 24. doi: 10.1016/j.eclinm.2019.01.003.