When the team first crunched the numbers, coffee seemed to have a detrimental effect on longevity. But people who drink coffee are more likely to smoke, and when the scientists took that into account (along with other demographic factors), the opposite appeared to be true.
Compared with men who didn't drink any coffee at all, those who drank just one cup per day had a 6% lower risk of death during the course of the study; those who drank two to three cups per day had a 10% lower risk, and those who had four to five cups had a 12% lower risk. For men who drank six cups or more, the apparent benefit waned slightly, with a 10% lower risk of death during the study compared with men who drank no coffee.
The relationship between coffee and risk of death was even more dramatic in women. Those who drank one cup per day had 5% lower odds of dying during the study compared with women who drank none. Those who consumed two or three cups a day were 13% less likely to die, those who downed four or five cups were 16% less likely to die, and those who drank six or more cups had a 15% lower mortality rate.