Java junkies can take some comfort from the finding that the risk was highest among light coffee drinkers (those who consumed up to one cup a day).
For those people, the risk of heart attack increased fourfold when they indulged.
Couch potatoes and those with other risk factors for heart disease were also at greater risk of having a heart attack after drinking a cup of coffee, the study showed.
As a result of these findings, "people at high risk for a heart attack who are occasional or regular coffee drinkers might consider quitting coffee altogether," says researcher Ana Baylin, a research associate at Brown University School of Medicine in Providence, R.I., in a news release.
Baylin, who works in the department of nutrition at Brown, adds that for these individuals, a cup of coffee could be "the straw that broke the camel's back."
Baylin and colleagues suggest caffeine causes short-term increases in blood pressure and sympathetic nervous activity that could trigger a heart attack.
On the other hand, previous studies have shown coffee drinkers may be at decreased risk for Parkinson's disease, diabetes and certain types of cancers.
Risk Highest For Light Drinkers
In the new study, moderate coffee drinkers (those who consumed two or three cups a day) raised their risk of having a heart attack by 60 percent by drinking a cup of coffee.
But light coffee drinkers increased their risk of heart attack by more than four times with one cup, according to the study.
Little effect was seen among heavy coffee drinkers — those who drank four or more cups per day.
What's more, coffee drinkers who have three or more risk factors for heart disease more than doubled their risk of sustaining a heart attack after downing a cup.
The new study was based on 503 cases of nonfatal heart attacks in Costa Rica.
The researchers asked participants about their coffee consumption in the hours and days before their heart attack.
Although the study was conducted in Costa Rica, the researchers say the results are relevant to the U.S. because Americans and Costa Ricans have similar caffeine habits.
Cutting The Risk
"For people with multiple risk factors for a heart attack and those who have a sedentary lifestyle, a cup of coffee could be the final straw," says Ahmed El-Sohemy, Ph.D., an assistant professor of nutrition at the University of Toronto. "One should aim to remove some of these known risk factors and have a more active lifestyle."
"For those people who are not regular consumers and have other risk factors, getting that jolt of caffeine is probably a jolt to their system," he explains. "We know that caffeine causes transient increases in blood pressure, so those who are not regular consumers are not used to it, and they get that surge and for a vulnerable heart, that could be the trigger."
El-Sohemy recently reported that people who have a genetic variation associated with slower caffeine metabolism are at an increased risk of a nonfatal heart attack when they consume coffee.
His findings appeared in the March 8 issue of JAMA, The Journal of the American Medical Association.
SOURCES: Baylin, A. Epidemiology, Aug. 2006; Vol. 17: pp. 506-511. Cornelis, M. JAMA, The Journal of the American Medical Association, March 8, 2006; Vol. 295: pp. 1135-1141. Ahmed El-Sohemy, Ph.D., assistant professor of nutrition, University of Toronto, Toronto, Canada.
By Denise Mann
Reviewed by Louise Chang, M.D.
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