NEW YORK (Reuters Health) – In a new study of 400,000 older Americans, those who reported drinking a few daily cups of coffee were less likely to die over the next 14 years than those who rarely or never drank it.
But that finding should be interpreted with caution, researchers said, because coffee habits were only measured at one point in time — and it’s unclear what ingredients in coffee, exactly, could be tied to a longer life.
“For those who do drink coffee, there’s no reason to stop. Periodically someone will say it’s bad, but I think this strengthens the view that it’s not harmful,” said Dr. Lawrence Krakoff, a cardiologist from the Mount Sinai School of Medicine in New York, who wasn’t involved in the new research.
“Whether it’s beneficial — without knowing the cause, it’s hard to say,” he told Reuters Health. “I wouldn’t encourage people to suddenly drink a lot of coffee with the expectation of benefit.”
Research on the long-term effects of coffee on various diseases has come to conflicting conclusions. Some studies suggest coffee drinkers are less likely to get diabetes, but others hint they may have a higher risk of heart disease.
For the new study, researchers at the National Institutes of Health in Rockville, Maryland used data from a diet and health study that started with nutrition surveys, including questions on daily coffee intake, given to adults between the ages of 50 and 71 in 1995 and 1996.
Researchers then tracked those participants through 2008, using national and state disease and death registries.
Initially, coffee drinking seemed to be tied to a higher chance of dying during the study period. About 13% of men and 10% of women who reported not drinking any coffee on their initial surveys died between 1995 and 2008, compared to 19% of men and 15% of women who’d said they drank six or more cups a day.
But coffee drinkers, it turned out, were also more likely to smoke, abuse alcohol and eat lots of red meat. When the researchers adjusted for those other behaviors, the data showed a different picture.
In that analysis, men who drank at least two cups of coffee a day were about 10% less likely to die during the study than those who abstained. For women, there was up to a 16% reduced risk of death in coffee drinkers compared to non-drinkers.
In particular, coffee was tied to a lower risk of dying from heart disease, stroke, injuries and accidents and infections — but not to fewer cancer-related deaths.
The links were similar when caffeinated and decaf coffee drinkers were analyzed separately, lead researcher Dr. Neal Freedman and his colleagues reported Wednesday in the New England Journal of Medicine.
The study was not without limitations, researchers noted, including that Dr. Freedman’s team only knew how much coffee participants were drinking at one point in the mid-1990s — and those patterns could have changed over time.
In past years, some researchers have been quick to jump to conclusions about the effects of coffee. For example, one 1981 study linking it to pancreatic cancer (also published in the New England Journal of Medicine) was later criticized for its methods.
“There have been false associations with coffee in the past,” Dr. Krakoff told Reuters Health. He said it’s important to be cautious about the new findings.
“My thinking is that these associations are very interesting but until you really link it to a causative mechanism, it remains vague.”
Because of the so-called observational design of the new study, it can’t prove that coffee was directly responsible for the lower risk of death in some participants.
Still, Dr. Freedman said there are a few possible explanations for why that might be the case. “We know that coffee has an effect on the brain, so it’s possible that may play a role,” he told Reuters Health. Or, “It may have an effect on bone health.”
But he agreed that until more research is done, no one should change their coffee-drinking behavior because of the findings.
“We really caution against that,” Dr. Freedman said. “We can’t be sure that coffee is having the effect that we saw and coffee contains many different compounds that can affect health in different ways.”
N Engl J Med 2012.