Nov. 1, 2010 -- Stroke risk increases in the hour after drinking a cup of coffee, but this risk reverses itself within two hours, a study shows.
The increased stroke risk is seen among occasional coffee drinkers or those who drink one or fewer cups of coffee a day.
The study is published in the November issue of Neurology.
Participants were asked about the amount of coffee they drank in the hour preceding their stroke and their typical coffee drinking habits. Seventy-eight percent said they drank coffee in the previous year.
Among people who reported drinking one cup of coffee a day or less, stroke risk doubled in the hour after they consumed a cup of coffee, the study shows.
“Coffee has been documented to have acute deleterious physiologic effects, including increased systolic and diastolic blood pressure. Compared to decaffeinated coffee, consumption of caffeinated coffee acutely increases stiffness in the arteries,” study researcher Elizabeth Mostofsky, MPH, writes in an email to WebMD.
Drinking More Than a Cup a Day
The new findings do not seem to apply to those who drank more than one cup of coffee per day.
It's possible that those who drink coffee more frequently may develop a tolerance to the short-term effects of caffeine, the researchers speculate.
There was also no increased risk seen among people who drank caffeinated tea or soda, possibly because there is a lower concentration of caffeine found in tea and soda compared to coffee, the researchers write.
It is hard to get reliable information about some of the events leading up to the stroke because many people are unable to speak after a stroke. The people in the new study had relatively mild strokes and were able to be interviewed. The findings may not apply to people who have more severe or fatal strokes, the researchers point out.
Most experts urge caution in interpreting the new findings on coffee intake and stroke risk. Other studies have found regular coffee drinking does not increase the risk of heart attack and stroke. Several studies have shown that drinking coffee reduces the risk of developing type 2 diabetes. What's more, there are many known, powerful risk factors for stroke that can be modified.
“While our study showed that there may be acutely increased risk of stroke in the hour following coffee intake, there is a vast literature on the beneficial effects of coffee on the risk of type 2 diabetes and no known long-term detrimental effects on cardiovascular disease. These findings suggest that habitual consumption may be healthy,” Mostofsky writes in an email to WebMD.
"We need further evidence to properly advise people about coffee intake, especially when other risk factors for stroke are present," writes Giancarlo Logroscino, MD, PhD, of the University of Bari, Italy, in an accompanying editorial.
"The big issue is that there may be something to this story, but controlling high blood pressure, high cholesterol, and stopping smoking is way more important for stroke prevention than stopping coffee," says Sahil Parikh, MD, a cardiologist at University Hospitals Case Medical Center in Cleveland.
Coffee drinking pales in comparison to established stroke risk factors, Parikh says. But "if you have other risk factors of stroke, you may want to be cautious."
"The data is still inconclusive, and it is difficult to make public health proclamations from this one study," says Ralph L. Sacco, MD, president of the American Heart Association and the chair of neurology at the University of Miami in Florida. "There are so many other more important vascular risk factors."
Don't overact, he says.
Patrick Lyden, MD, the chair of the department of neurology at Cedars-Sinai Medical Center in Los Angeles, says the jury is still out on caffeine as a risk factor for stroke. "This is one more study in a long line of studies on the health benefits and health risks of caffeine," he says. "This is completely different than cigarette smoking where study after study reported risks."
His advice? "Stay tuned. We don't have the final answer on caffeine and stroke risk yet."
A spokesman for a coffee trade group says coffee has been given a clean bill of health in most studies. “The vast body of research over many years has found no negative effects of coffee on cardiovascular health and, in fact, has shown many health benefits like protection against diseases such as Alzheimer’s, Parkinson’s, diabetes and liver damage and cancer,” says Joe DeRupo, a spokesman for the National Coffee Association, a trade group representing the coffee industry.