Puffing & positive? Science says smoking weed can hurt your heart
A recent article published in Clinical Infectious Diseases reports results from a study investigating the impact of marijuana on the heart health of people living with HIV. Although there was no significant association between marijuana use and HIV disease progression or death, long-term “heavy” marijuana use was associated with increased inflammation and mid-life cardiovascular problems in HIV-positive men.
“Our study shows that heavy marijuana smoking increases cardiovascular risk in middle-aged HIV-positive men, independent of tobacco smoking and other risk factors,” said Dana Gabuzda, MD, from Dana-Farber Cancer Institute. “This increased cardiovascular risk is additive in HIV-positive men who smoke both marijuana and tobacco. Given these findings, physicians should caution HIV-positive patients about this potential risk, especially those who smoke both marijuana and tobacco, or have other known risk factors such as elevated lipids.”
Marijuana use is becoming more common as laws allowing the sale, distribution and use of marijuana are passed in places across the U.S. A Gallup Poll in 2016 found that 13% of U.S. adults currently smoke marijuana, up from 7% in 2013.
People living with HIV may be even more likely to use marijuana, to ease symptoms caused by HIV-related conditions, treat side effects of antiretrovirals, or for other reasons. A recent study found that HIV-positive men were more likely to be “chronic high” users of marijuana than HIV-negative men, and another study found that about a quarter of people living with HIV reported marijuana use.
“It is widely believed that smoked marijuana is relatively harmless,” said Gabuzda. “Considering rapid growth in marijuana use for recreational or medicinal purposes, we need to know which modes of use—smoked versus vaped or edible—optimize its positive effects while minimizing adverse effects.”
Details of the study
The study published in CID found that “heavy” long-term marijuana use increased the risk of heart disease but that people who used marijuana occasionally did not have this increased risk. (“Heavy” long-term users were those people who reported using marijuana daily or weekly at more than half of the study visits.)
Data from a total of 558 men living with HIV from the Multicenter AIDS Cohort Study (MACS) were included in the analyses. The median age of participants at baseline was 40.8 years. About 20% of participants were classified as heavy marijuana users.
A higher proportion of heavy marijuana users had cardiovascular events like heart attacks, heart disease and atherosclerosis (hardening of the arteries) between the ages of 40 and 60 than participants who did not use marijuana or used it occasionally. Cardiovascular events occurred in 19.7% of heavy marijuana users compared with 8.7% of non-users and people who used marijuana occasionally.
Cardiovascular event rates were also higher among people who smoked cigarettes (which are known to increase cardiovascular event risk), and rates were highest among men who used both marijuana and smoked cigarettes.
What about for people who consume edibles?
The participants in this study were not asked to report how they ingested marijuana, but the researchers reasoned that “the predominant mode of exposure was likely via marijuana smoking.”
Gabuzda explained that the safety profile of smoked marijuana is likely to be different from that of edible forms, since marijuana smoke contains combustion products including polyaromatic hydrocarbons and VOCs (volatile organic compounds). In small amounts, exposure to combustion products may pose minimal risk, but may cause harm in people with pre-existing risk factors for heart and lung disease, she said.
More research is needed to better define the risks associated with long-term or daily ingestion of marijuana edibles, said Gabuzda, since the results from this study only apply to people who smoke marijuana.
“Edibles may have other risks, such as unintentional intoxication or overdose. THC delivery by ingestion is slower and it is often harder to control the exact doses delivered by edible forms. We need more research on different modes of marijuana intake to better understand their dosing and safety profiles, and how to optimize delivery for therapeutic purposes,” she said.
The effect of smoking marijuana on inflammation
The study also found that frequent, long-term marijuana smoking was also associated with increased white blood cell counts (which is a measure of inflammation).
“Our finding that heavy marijuana smoking is associated with increasing WBC count suggests that increased inflammation may be an unintended consequence of heavy exposure to smoked marijuana in middle-aged HIV-positive men,” said Gabuzda.
This inflammation is not related to the plant-derived components of marijuana (THC and cannabidiol), explained Gabuzda, but rather from the toxic combustion products found in smoke. When marijuana is delivered by ingestible modes, these toxic chemicals are not present.
Lorenz, D. R., Dutta, A., Mukerji, S., Holman, A., Uno, H. and Gabuzda, D. Marijuana use impacts midlife cardiovascular events in HIV-infected men. Clinical Infectious Diseases, 2017.