November 12, 2019
Both studies will be presented at this weekend's American Heart Association (AHA) Scientific Sessions 2019 in Philadelphia.
In the observational stroke study, young adults with recent marijuana use had almost twice the risk compared with non-users of having had a stroke, and the risk increased further among frequent marijuana users. The risk of having had a stroke was even higher — three times that of non-users — in frequent marijuana users who also smoked cigarettes.
"Our results suggest that there is a link between the frequent use of marijuana and the risk of stroke, and the risk is higher if marijuana is used in addition to cigarettes or e-cigarettes," lead author Tarang Parekh, MBBS, a health policy researcher at George Mason University in Fairfax, Virginia, told Medscape Medical News.
"As this was an observational, cross-sectional study with many limitations, our findings should be regarded as hypothesis-generating and need confirmation, preferably from longitudinal studies. However, I don't think we should ignore these findings and marijuana use should be considered a risk factor for stroke," he added.
"Even though cannabis is not thought to be as harmful or addictive as some other recreational drugs such as opiates, we cannot ignore the potential health risks," Parekh said.
Synthetic versions of cannabis are now available, and the product has been legalized in almost half of US states for medical use, he noted. "Its use is increasing but we don't have enough information on potential health risks."
Patients are now commonly asking their doctors about the medical use of cannabis for various conditions, he added, "and it is important for us to be aware of potential health risks, and these may include stroke."
For the study, the researchers analyzed data on 43,860 young adults (aged 18-44) from the Behavioral Risk Factor Surveillance System, a US nationwide cross-sectional survey conducted by the US Centers for Disease Control and Prevention. Participation was voluntary and anonymized, and information was collected by telephone interview.
Among many questions, participants were asked if they had used marijuana within the last month, and if so, how frequently. They were also asked if they had ever had a stroke. All information on both marijuana use and history of stroke was self-reported.
Results showed that 13.6% of the cohort reported marijuana use in the past 30 days. The use of marijuana was significantly higher among 18- to 24-year-olds, males, and non-Hispanics. Marijuana users were more often current combustible cigarette users and current e-cigarette users and heavy alcohol drinkers compared with nonusers. However, diabetes mellitus, hypertension, and hypercholesterolemia were less frequently observed among marijuana users.
Compared with nonusers, recent marijuana users showed an 82% higher risk of stroke, with an adjusted odds ratio of 1.82 (95% confidence interval, 1.08 - 3.10). This further increased to an odds ratio of 2.45 (95% CI, 1.31 - 4.60) with frequent recent use of marijuana defined as more than 10 days per month.
When controlled for hypertension and cholesterol, stroke odds were three times higher with recent marijuana use, odds ratio 3.11 (95% CI, 1.23 - 7.79), and four times higher, odds ratio 4.10 (95% CI, 1.22 - 13.69), with frequent recent use.
On further risk stratification, even higher risks of stroke were seen in frequent marijuana users who also reported current combustible cigarette use, odds ratio 3.12 (95% CI, 1.40 - 6.97), or current e-cigarette use, odds ratio 2.63 (95% CI, 1.07 - 6.46).
"We found that young marijuana users had higher odds of stroke even after adjusting for concomitant substance use, and a greater odds of stroke in frequent marijuana use with current combustible cigarette and e-cigarette use," Parekh said.
On potential mechanisms behind the observations, he noted that recent studies have reported that heavy and chronic marijuana use can lead to multifocal intracerebral vasospasm, multifocal intracranial stenosis, cardiac embolization, systemic hypotension, altered vasomotor function, other cerebrovascular dysfunctions, and procoagulant effects on platelets — all of which could increase the stroke risk.
Parekh pointed out several limitations of the study, including that its cross-sectional nature and retrospective review of the database and the self-reporting of stroke episodes/marijuana use may have led to bias; he added that the cross-sectional design may limit the causality between marijuana use and stroke.
"Despite these limitations, the Behavioral Risk Factor Surveillance System data offer larger sample size, improved questionnaire design, and interviewing, data collection, and processing methods for the national representation," he concluded.
Commenting on the study, Robert Harrington, MD, current AHA president and professor of medicine at Stanford University, California, cautioned that the observational design of the study meant that confounding could be an issue.
"These particular authors tried to adjust for that as best they can, and they looked to have done a reasonably good job with that and did find that cannabis use was associated with an increased risk of stroke," he said.
"It is not definitive, and would be considered moderate quality of evidence, not a high quality of evidence," Harrington noted.
"But it is important because as we see that states are increasingly legalizing use of marijuana or cannabis-containing products — in part because of assumed health benefits — we at the AHA feel that it's important that those health benefits actually be confirmed," he added, "because there's actually surprisingly little rigorous scientific information on the health benefits of these products. And so, in that regard, this study is important."
Link With Cardiac Arrhythmia
In a separate study, younger individuals diagnosed with cannabis use disorder had a 50% greater risk of being hospitalized for an arrhythmia compared with non-users.
Cannabis use disorder is characterized by frequent, compulsive use of marijuana, similar to alcoholism.
In the study, young African American men (aged 15-24) with the disorder had the greatest risk of being hospitalized for arrhythmia, although cannabis use disorder was more common among white men aged 45 to 54 years.
"The effects of using cannabis are seen within 15 minutes and last for around 3 hours. At lower doses, it is linked to a rapid heartbeat. At higher doses, it is linked to a slow heartbeat," said study author Rikinkumar S. Patel, MD, Griffin Memorial Hospital in Norman, Oklahoma.
"The risk of cannabis use linked to arrhythmia in young people is a major concern, and physicians should ask patients hospitalized with arrhythmias about their use of cannabis and other substances because they could be triggering their arrhythmias," said Patel.
As medical and recreational cannabis is legalized in many states, he added, "it is important to know the difference between therapeutic cannabis dosing for medical purposes and the consequences of cannabis abuse. We urgently need additional research to understand these issues."
For the study, the researchers conducted a retrospective analysis of the Nationwide Inpatient Sample from 2010 to 2014. They compared 570,000 patients (aged 15-54 years) who had a primary diagnosis for arrhythmia with 67.6 million non-arrhythmia patients hospitalized for other conditions, with results adjusted for demographics and comorbid risk factors.
Results showed that the incidence of cannabis use disorder in arrhythmia inpatients was 2.6%. Patients with cannabis use disorder were more likely to be younger, male, and African American.
While cannabis use disorder was not associated with higher odds for arrhythmia hospitalization in the whole population after adjustment for demographics and comorbid risk factors (including tobacco and alcohol abuse), it was associated with increased arrhythmia risk in younger people.
The odds ratio was 1.28 (95% CI, 1.23 - 1.35) in those aged 15-24 years and 1.52 (1.47 - 1.58) in those aged 25-34 years.
"Our study found that cannabis use disorder is independently associated with a 47% to 52% increased likelihood of arrhythmia hospitalization in the younger population, and so physicians need to familiarize with cannabis abuse or dependence as a risk factor for arrhythmia," they conclude.
The authors of both studies have disclosed no relevant financial relationships.