Cannabis smoking is an independent risk factor for lung disease in people with HIV

According to a study by a group of scientists from the United States, frequent smoking of cannabis is a risk factor for lung disease in men living with HIV. It increases the likelihood of disease, especially in cases where there is an infectious cause, and does not depend on smoking tobacco and the number of CD4 cells.

The study involved about 2.5 thousand men who have sex with men (MSM), and half of them were HIV-positive. There were no independent associations between smoking cannabis and lung disease in HIV-negative men, indicating that PLHIV are particularly vulnerable to lung diseases caused by smoking cannabis.

“As far as we know, this study is the largest to date study of diagnoses of lung diseases among HIV-positive [cannabis] users,” the authors comment.

“Daily or weekly smoking of marijuana, as we were able to establish, is associated with an increased risk of infectious lung diseases among participants living with HIV [...] Constant smoking of marijuana was also associated with an increased risk of chronic bronchitis,” the researchers said.

The authors believe that their findings are important for proper care of people with HIV, and that addressing the problem of cannabis use should help reduce the incidence of lung diseases in this group.

It is well known that people with HIV have an increased risk of lung disease. This is partly due to the high level of smoking among HIV-positive people. However, the damage to the body and immune system caused by HIV are also important reasons for establishing these diagnoses.

Studies involving HIV-negative people have shown that smoking cannabis is a risk factor for the onset of respiratory symptoms, such as coughing and shortness of breath, as well as chronic obstructive pulmonary disease (COPD) and emphysema. However, until now, relatively little has been known about cannabis smoking as a risk factor for lung disease in patients with HIV.

A group of specialists from the United States within the framework of the ongoing multicenter cohort study on AIDS (MACS) has developed a program that compares the incidence of infectious lung diseases (for example, pneumonia) and non-communicable diseases (for example, bronchitis) between HIV-positive and HIV-negative gays and other MSM systematically use cannabis. The analysis also suggested an assessment of other risk factors for lung diseases, especially tobacco smoking and CD4 cell count in HIV +.

The study population consisted of 2704 men aged 30 years. Half of them were HIV positive. Participants were selected for the period from 1996 (the first combination of ART was introduced) until 2014. The average follow-up was just over ten years. Participants were asked about the frequency and intensity of cannabis and tobacco smoking, as well as about their diagnoses of lung diseases (the latter were also checked using medical records).

The average age of participants was 44 years old, two thirds of them were white. The majority (90%) of HIV-infected patients received ART, and in 60% the number of CD4 exceeded 350 cells / mm3.

Weekly or daily smoking of cannabis lasting at least one year was registered in 27% of HIV-positive people and in 18% of HIV-negative people. The average duration of daily / weekly smoking of cannabis was about four years for both groups.

Tobacco smoking was slightly higher among people with HIV (65% vs. 61%).

The incidence of pulmonary diseases caused by infectious causes was also significantly higher among HIV-positive patients (33% vs. 22%).

The same applies to non-infectious lung diseases (21% versus 17%).

A more thorough analysis showed that in patients with HIV who smoke cannabis, rates of both infectious and non-infectious lung diseases were significantly higher than among those who smoked tobacco (41% versus 30%; 25% versus 19%). This result was not reproduced in the HIV-negative group (24% versus 21%; 15% versus 18%).

Among HIV-positive participants, the most significant risk factor for the diagnosis of lung infection was CD4 cell count below 200 cells / mm3 (aHR = 3.37; 95% CI, 2.58-4.41, p <0.001). Systematic smoking of cannabis was also among the risk factors (aHR = 1.34; 95% CI, 1.06-1.71, p = 0.016).

After taking into account the number of CD4 cells and smoking status, the fact of systematic daily or weekly use of cannabis showed an increase in the risk of diagnosing an infectious lung disease by 48% (aHR = 1.48; CI: 1.05-1.75, p = 0.035) with prolonged habit and by 10% (CI: 1.04-1.16, p = 0.012) in the case of smoking the substance for two years. Experts note that the risks are significantly increased by smoking tobacco.

As scientists have established, no association was found between cannabis smoking and infectious lung disease among HIV-negative participants.

Turning to non-infectious diseases of lungs the authors noted that cigarette smoking, like regular cannabis use, was a serious risk factor for chronic bronchitis among men living with HIV (HR = 1.54; CI 95%, 1.11 -2.13, p = 0.0093). However, at the same time, no significant association was observed between cannabis smoking and noncommunicable lung diseases in HIV-negative people.

“These data confirm the well-known link between HIV infection and the increased prevalence of lung diseases and provide us with evidence that HIV-positive individuals may be more vulnerable to the effects of marijuana on the lungs than non-infected participants,” experts say.

The risk of infectious lung disease in HIV patients with daily or weekly cannabis use was equivalent to smoking ten cigarettes a day.

“Smoking marijuana is a complex risk factor that health care professionals should consider when carrying out the prevention or treatment of lung diseases in people living with HIV,” the authors conclude.