Marijuana abuse linked to increased MI risk

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Washington – Marijuana abuse was independently associated with an eye-opening doubled risk of acute MI in a large, retrospective, age-matched cohort study, Ahmad Tarek Chami, MD, reported at the annual meeting of the American College of Cardiology.

The link was strongest by far in young adult marijuana abusers, with an adjusted 3.2-fold increased risk of MI in 25- to 29-year-olds with marijuana abuse noted in their medical records, compared with age-matched controls and a 4.56-fold greater risk among the 30- to 34-year-old cannabis abusers, according to Dr. Chami of Case Western Reserve University in Cleveland.

 Dr. Ahmad Tarek Chami

Dr. Ahmad Tarek Chami

“Our study raises the possibility [of] an association between cannabis and MI independent of age, hypertension, diabetes, smoking, and abuse of other substances,” he observed.

These data constitute a signal warranting further research. Public opinion regarding potheads has undergone a huge shift. Medical and/or recreational marijuana is now legal in 28 states and the District of Columbia. Surveys indicate that, in 2015, 8.3% of Americans aged 12 years and older had used marijuana during the previous month, and 13.5% had used it within the past year.

“Cardiologists and other physicians are more likely than ever before to encounter patients who use marijuana or even ask them to prescribe it,” Dr. Chami said.

The cannabis plant contains more than 60 cannabinoids. Although marijuana is widely prescribed for treatment of nausea, anorexia, neuropathic pain, glaucoma, seizure disorders, and other conditions, the long-term effects of marijuana on the cardiovascular system are largely unknown, he continued.

This ambiguity was the impetus for Dr. Chami’s study. In it, he utilized a database incorporating 26 health care systems across the United States with nearly 50 million patients, which is maintained by Explorys, an 8-year-old Cleveland-based company.

Dr. Chami identified 210,700 patients with cannabis abuse noted in their medical records, covering provider/patient encounters between October 2011 and September 2016. Their mean age was 36.8 years. The abusers were age-matched to 10,395,060 non–marijuana abuser controls.

The 5-year cumulative incidence of MI in this skewed–young patient population was significantly higher than in the marijuana abuser group: 1.28%, compared with 0.89%, for a 44% increase in relative risk.

However, the marijuana abusers also had a significantly higher burden of cardiovascular risk factors than did their non–cannabis abusing counterparts. They were 2.85 times more likely to have hypertension, 1.59 times more likely to be dyslipidemic, and 7.2 times more likely to be cigarette smokers, and they had a 2.8 times greater prevalence of diabetes. Of note, they were also 17.6 times more likely to have been diagnosed with alcohol abuse, and 61 times more likely to abuse cocaine.

In a multivariate analysis adjusted for these and other potential confounders, marijuana abuse remained independently associated with a 1.73-fold increased risk of acute MI. Moreover, after eliminating patients with known coronary artery disease, the strongest risk factor for MI, from the analysis, marijuana abuse was independently associated with a twofold increased risk of MI.

This was a retrospective study, one limitation of which was the standard caveat regarding the possibility of unrecognized confounders that couldn’t be taken into account.

Another study limitation is the uncertainty regarding the diagnosis of “cannabis abuser” in patients’ charts. The Explorys cloud-based database relies on ICD codes to capture data. It doesn’t include specific information on how much marijuana a patient who was labeled as an abuser was actually using. This limitation raises an unanswered question: Were young adults who abused marijuana at highest risk for MI because of heavier use, or are younger patients’ coronary arteries somehow more vulnerable to marijuana’s potential adverse cardiovascular effects?

Several audience members called Dr. Chami’s study “very provocative.” Aaron D. Kugelmass, MD, said that the fundamental question in his mind is whether the cardiovascular hazard of marijuana identified in this study is the result of the practice of smoking the raw product, usually associated with illicit marijuana abusers.

Today, legalized marijuana is often consumed in the form of edible products, tinctures, and other derivatives that don’t involve inhalation of smoke. Whether these alternative forms of consumption pose any cardiovascular risk is an important unresolved issue in this era of widespread decriminalization of cannabis, noted Dr. Kugelmass, chief of cardiology and medical director of the Heart and Vascular Center at Baystate Medical Center in Springfield, Mass.