One of the questions that gets posed to me regularly as a physician is: “Is coffee bad for me?”
Well, a wonderful study was published in the Aug 18 edition of the New England Journal of Medicine called “Association of Coffee Drinking with Total and Cause-Specific Mortality.” The short answer is, “Coffee may actually be healthy.”
The study followed approximately 400,000 people, aged 50 to 71, from 1995 to 2008 (that is an enormous database). People were asked their coffee drinking habits at the start of the study (it is presumed their habits were set given the age of people followed).
During this 13 year period, 13% of the cohort died. (Remember, the average age at the start of the study was 61 years.)
The key result: When adjusted for other variables, people who drank coffee had a 10% lower risk of dying in this period. (The risk was reduced by 6% for those who drank one cup of coffee and by about 10% for those who drank 2 or more cups. This same risk reduction was seen even in those people who drank more than 6 cups of coffee per day.)
It is important to note that the benefit was only seen after adjusting the data. The reason . . . coffee drinking was associated with smoking. Smokers are known to have a higher mortality from cancer, heart disease, etc. Without any adjustments, the coffee drinkers had a higher mortality. However, when removing the increased risk known to result from smoking, that is when the benefit is observed.
What does this mean in simple terms? For 100 people aged 61 looking ahead to the next 13 years, about 13 non-coffee drinker would be expected to die versus 11-12 deaths for coffee drinkers.
One huge limitation . . . this study does not address the question of causation versus correlation. Specifically, does drinking coffee really have some beneficial effect? Or do coffee drinkers tend to have some other habit that confers the benefit, and drinking coffee is an unrelated behavior? This study does not have the answer. Interestingly, the benefit was conferred whether the coffee consumed was regular or decaf. If coffee itself really does have a benefit, this suggests is might not be caffeine.
One last note (supporting the conclusions): Two other recent large studies (the Health Professionals Follow-up Study and the Nurses Health Study) suggest benefits that are similar or even a little bit better to that observed here.
While this study leaves many questions unanswered, it is a reasonable conclusion that coffee does not seem to harmful, and it might indeed have a health benefit.
So, if anyone gives you a hard time for drinking coffee, now you can tell them, “I’m taking my vitamin!”
source: N Engl J Med 2012; 366:1891-1904: http://www.nejm.org/doi/full/10.1056/NEJMoa1112010