Cumulative marijuana use not linked to subclinical atherosclerosis

There appears to be no link between the average population level of marijuana use and subclinical atherosclerosis in a middle-aged population in the US, according to a recent study. However, tobacco smoking remains strongly associated with increased carotid intima-media thickness (CIMT).

“Though the broader public health implications of high prevalence of tobacco use among marijuana users is alarming, this study adds to the growing body of evidence that there is no association between a moderate level of marijuana use and cardiovascular disease and markers of subclinical atherosclerosis,” the researchers said.

This study examined the relationship between CIMT in midlife and lifetime exposure to marijuana (1 marijuana year=365 days of use) and tobacco smoking (1 pack-year=20 cigarettes/day for 365 days) using data from the Coronary Artery Risk Development in Young Adults (CARDIA) study, which included 5,115 Black and White women and men at year 20 visit.

The researchers measured CIMT by ultrasound and defined high CIMT at the threshold of the 75th percentile of all examined participants. They also used logistic regression models stratified by tobacco smoking exposure, adjusting for demographics, cardiovascular risk factors, and other drug exposures.

Of the participants, 3,257 had complete data: 2,722 (84 percent reported ever marijuana use and 374 (11 percent) were current users; 1,539 (47 percent) reported ever tobacco smoking and 610 (19 percent) current smokers. [Am J Med 2021;134:777-787.E9]

Multivariate analysis revealed no link between cumulative marijuana exposure and high CIMT in never or ever tobacco smokers (odds ratio [OR], 0.87, 95 percent confidence interval [CI], 0.63–1.21 at 1 marijuana-year among never smokers; OR, 1.11, 95 percent CI, 0.85–1.45 among ever tobacco smokers).

Notably, a robust association was observed between cumulative exposure to tobacco and high CIMT (OR, 1.88, 95 percent CI, 1.20–2.94 for 20 pack-years of exposure).

“Previous analyses of CARDIA participants showed no association between marijuana use and cardiovascular events or mortality overall, [b]ut the study population was only around 50 years old, so participants had not yet reached the age at which cardiovascular disease usually occurs,” the researchers said. [Am J Public Health 1997;87:585-590; Am J Public Health 2017;107:601-606]

“Therefore, we used markers of subclinical atherosclerosis as indications of increased future cardiovascular risk,” they added.

No previous studies on marijuana and CIMT were identified, but there were two studies testing the relation between abdominal artery and coronary artery calcium and cumulative marijuana use. [Addiction 2018;113:845-856; Lancet 2011;377:732-740]

“Our results align with the results of both these studies, especially the strong expected association between cumulative tobacco exposures and markers of subclinical atherosclerosis,” the researchers said. “These studies did not report an association between cumulative marijuana use and subclinical atherosclerosis either.”

Residual confounding from tobacco smoking might explain the single association between marijuana-years in ever tobacco smokers and common CIMT modeled as a continuous variable, because tobacco smoking and marijuana use are associated. [Addiction 2018;113:845-856; Harm Reduct J 2005;2:21]

“It may also be a chance finding because we ran multiple analyses that used varying definitions of CIMT,” the researchers said.

“Because most of the study population occasionally used marijuana, in line with the typical frequency of use in the general population, future studies are needed in populations who engage in high-intensity marijuana use,” they noted.