Older people who reported drinking a few daily cups of coffee were less likely to die over the subsequent 14 years than were those who abstained from the beverage or rarely drank it, according to a US study of 400,000 people.
In particular, coffee was tied to a lower risk of dying from heart disease, stroke, infections, injuries and accidents, the researchers said in a report published in the New England Journal of Medicine.
But they warned that the findings should be interpreted with caution because coffee habits were only measured at one point in time - and it's unclear what ingredients in java, exactly, could be tied to a longer life.
"We know that coffee has an effect on the brain, so it's possible that may play a role," said lead researcher Neal Freedman at the National Institutes of Health in Rockville, Maryland. "Or, it may have an effect on bone health."
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 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 Lawrence Krakoff, a cardiologist from the Mount Sinai School of Medicine in New York, who wasn't part of the study.
"Whether it's beneficial - without knowing the cause, it's hard to say. I wouldn't encourage people to suddenly drink a lot of coffee with the expectation of benefit."
For their data, researchers pulled from a diet and health study that started with nutrition surveys including questions on coffee intake given to adults ages 50 to 71 in 1995 and 1996.
Researchers then tracked those participants through 2008, using national and state disease and death registries to figure out how many of them died, and from what.
Initially, coffee 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 downed 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 took into account these other behaviors, the data showed a different picture.
In that analysis, men who drank anywhere from two to more than six 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.
The study was not without limitations, researchers noted, including that Freedman's team only knew how much coffee participants drank at one point in the mid-1990s, and those patterns could have changed over time.
"My thinking is that these associations are very interesting but until you really link it to a causative mechanism, it remains vague," Krakoff said.
Researchers said that until more research is done, nobody should change their coffee habits because of the findings.
"We really caution against that. We can't be sure that coffee is having the effect we saw and coffee contains many different compounds that can affect health in different ways," Freedman said.