Marijuana users may have a shorter life expectancy after suffering a heart attack than people who do not use the drug, a new study suggests.
With the ageing of the Baby Boomer generation, a growing percentage of Americans are long-time marijuana users. A 2002 national survey found that the number of 45- to 64-year-olds who reported marijuana use was three times higher than it had been 10 years earlier.
In a new study, Dr Kenneth J. Mukamal of the Beth Israel Deaconess Medical Centre in Boston and associates found that these ageing marijuana users may have a poorer prognosis in the years following a heart attack.
Among more than 1,900 heart attack patients the researchers followed, those who reported regularly smoking marijuana in the year before the attack were two to four times more likely to die within the next 4 years.
"Although marijuana use has not been associated with mortality in other populations, it may pose particular risk for susceptible individuals with coronary heart disease," the researchers report in the American Heart Journal.
Marijuana has a number of effects that could be dangerous for older adults with risk factors for a heart attack, according to Mukamal's team.
The drug triggers a spike in resting heart rate, as well an increase in blood pressure. At the same time it speeds heart rate, creating a greater demand for oxygen, it can also limit the body's ability to use oxygen, the researchers explain.
Marijuana smoke exposes users to carbon monoxide, and one study found that the drug may be even worse than cigarettes when it comes to draining heart attack survivors' capacity for exercise.
Mukamal and his colleagues based their findings on 1,913 US men and women who were interviewed within a few days of being hospitalised at 1 or 45 centres for a heart attack. Among other questions, they were asked whether they had smoked marijuana in the past year. Fifty-two patients said they had.
Over the next several years, 317 patients died, with the risk being higher among marijuana users. Those who'd said they smoked less than once a week had 2.5-times the risk of death of compared with non-users, while heavier users had a 4.2-times higher risk of death.
Marijuana users had higher odds of dying from both cardiovascular causes and causes unrelated to their hearts. These elevated risks remained even when Mukamal's team factored in the effects of cigarette smoking, a habit common among marijuana users.
The study "raises concerns" about the risks of marijuana use, particularly for people already at risk of heart attack and stroke, according to an editorial published with the study.
More research is needed into both the short- and long-term effects of marijuana use in older adults and others with heart attack risk factors, writes Dr J. Michael Gaziano of Harvard Medical School.
"In the meantime," he concludes, "it seems advisable to continue to discourage marijuana use in our patients, especially those with known (cardiovascular disease) or risk factors." - (Reuters Health)
SOURCE: American Heart Journal, March 2008.
How deadly is pot?
Pot smoking may raise stroke risk