June 14, 2001 BOSTON – Researchers at Beth Israel Deaconess Medical Center and their colleagues have found that people who smoke marijuana may increase their risk of a heart attack. In a study of nearly 4,000 people who had suffered a heart attack, the researchers observed that a person’s chance of having a heart attack, particularly those who are already at risk for heart disease, increased nearly five times during the first hour after smoking marijuana.
These findings, published in the June 12 issue of Circulation, may become more relevant as baby boomers, who are more likely that previous generations to smoke marijuana, enter the age at which heart disease is more common.
“People’s risk for coronary artery disease increases as they enter their 40s and 50s, so the risks associated with smoking marijuana, which might have been a trivial issue when people were younger, may now pose a significant health concern,” says lead author Murray Mittleman, M.D., Dr.P.H., and director of cardiovascular epidemiology at Beth Israel Deaconess.
Marijuana is considered the most widely used illicit drug in the U.S. More than an estimated 72 million Americans have smoked marijuana or hashish at least once in their lifetime. New evidence suggests that there is a shift in the age distribution of marijuana users, with regular use on the rise among people in their 30s, 40s, and 50s. A recent Institute of Medicine report notes that even if marijuana use poses no medical risk for healthy young adults, any effect of marijuana use on cardiovascular health among middle aged and older adults could have a significant impact on public health.
For this new study, Mittleman and his colleagues interviewed 3,882 heart attack patients, as part of the multicenter Determinants of Myocardial Infarction Onset Study. Study participants were interviewed an average of four days after a heart attack. They included men and women from age 20 to 92. More than half of the study subjects were men. On average, marijuana users were about 44 years old. Twenty-three percent of the participants who smoked marijuana were between 50 and 69 years old.
Of the 124 patients who reported using marijuana in the past year, only nine were found to have smoked marijuana in the hour before their heart attack. Even though marijuana use was rare among study participants, the researchers found that in the hour after smoking marijuana the relative risk of heart attack increased 4.8 times. To evaluate relative risk, comparisons were made between the frequency of marijuana use in the hours preceding heart attack symptoms and the frequency of marijuana use over the past year, as recalled by study participants. When compared to non-users, marijuana smokers were more likely to be men. They also were more likely to be obese and to smoke cigarettes. A history of angina and high blood pressure was less common among individuals who smoked marijuana.
While smoking marijuana was found to be less risky as an immediate trigger of heart attack than using cocaine, it is roughly as dangerous as exercise for a fit person and more dangerous than sex for a sedentary person.
Studies have shown that marijuana use increases heart rate, but it is not entirely clear how marijuana may trigger a heart attack. One school of thought is that the drug may trigger a heart attack by causing existing coronary plaques to rupture and clot, restricting blood flow to the heart. Mittleman, who also is an assistant professor at Harvard Medical School and Harvard School of Public Health, says more studies are needed to understand the various pathways that are leading from the external stressors to the occurrence of heart attack. Once this information is in hand, he adds, investigators might be able to develop novel strategies to prevent heart attacks.
“Our study provides new information for the debate on the medical uses of marijuana and highlights the importance of considering the potential benefits and risks of taking any substance for medical use,” concludes Mittleman.
The study’s coauthors are Rebecca Lewis, Beth Israel Deaconess, Malcolm Maclure, Sc.D., and Jane Sherwood, R.N., both from Harvard School of Public Health, and James Muller, M.D., Massachusetts General Hospital.
Study funding came from the National Heart, Lung, and Blood Institute and the American Heart Association.
Beth Israel Deaconess Medical Center is a major patient care, research and teaching affiliate of Harvard Medical School and a founding member of CareGroup Healthcare System. Beth Israel Deaconess is the third largest recipient of National Institutes of Health research funding among independent U.S. teaching hospitals.
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The above story is based on materials provided by Beth Israel Deaconess Medical Center.
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