News Release

Aging marijuana smokers face sharply higher risk of heart attack soon after using drug

Peer-Reviewed Publication

American Heart Association

SAN DIEGO, March 2 -- Middle-aged and elderly marijuana users increase their risk of a heart attack by more than four and a half times during the first hour after smoking the drug, according to a study being presented today at the American Heart Assocation's 40th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.

"To my knowledge, this is the first study to document that smoking marijuana can trigger a heart attack," says Murray A. Mittleman, M.D., Dr.P.H., director of cardiovascular epidemiology at Boston's Beth Israel-Deaconess Medical Center. "It increases the heart rate by about 40 beats per minute," he says. "It also causes the blood pressure to increase when the person is lying down, and then abruptly fall when the person stands up, often causing dizziness. These effects may pose significant risk, especially in people with unrecognized coronary disease."

Researchers collected detailed information on marijuana use in 3,882 patients who had suffered heart attacks. Of these, 124 were identified as current marijuana users, including 37 who reported smoking the drug within 24 hours before their heart attack, and nine who had used it within an hour of the onset of symptoms.

"We found that during the first hour after use, the risk of a heart attack is 4.8 times higher than during periods of non-use," says Mittleman. "In the second hour, the risk drops to 1.7 times higher than during periods of non-use. This indicates a rapid decline in the dangerous effects of marijuana on the heart, but the short-term risk is considerable, especially for patients with other risk factors."

Based on the study, the cardiac risks to individual users posed by marijuana appear to be much lower than those associated with cocaine use, which causes much sharper rises in both heart rate and blood pressure, Mittleman says. However, he adds that the overall public health threat from marijuana could be even greater than from cocaine because marijuana use is believed to be more widespread.

The study's findings provide "possible new food for thought" in the ongoing controversy over whether marijuana use for medical purposes should be legalized, he says.

In a 1996 referendum in California, voters approved the legal medical use of marijuana, and since then, at least seven other states have passed laws allowing physicians to prescribe the drug, although it is still prohibited by federal law, Mittleman says.

A recent report by The Institute of Medicine, of the National Academy of Sciences, found no significant marijuana-related cardiac risk among younger users, he says. "But part of the problem lies in the fact that we now have millions of baby boomers who are reaching the age when the risk of coronary heart disease increases for both men and women," Mittleman adds.

"Many of these people were users of marijuana when they were in their teens and 20s, and a sizable percentage of them may still use the drug, either frequently or occasionally," he says.

"They should at least be aware that their risk of a heart attack suddenly soars each time they smoke the drug."

Mittleman says researchers still aren't sure whether it's the marijuana itself that causes the increased risk of heart attack, or whether it's other components in the smoke such as carbon monoxide, or a combination of the two. "This is an area that warrants further study," he says.

Co-authors are Rebecca A. Lewis, Malcolm Maclure, Sc.D.; Jane B. Sherwood, R.N.; and James E. Muller, M.D.

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Media advisory: Dr. Mittleman can be reached at (617) 632-7653. (Please do not publish telephone number.)


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