Longer life with an extra espresso shot? Let's carefully consider the data.

May 23 2012 Published by under Physiology/Pharmacology

I realize this study is SO last week, which is about two months in dog years and a decade in internet years, but seeing as I'm about to lend my dulcet tones and my delicate opinions to Skeptically Speaking on this topic, I feel I must needs blog this paper.

That, and it's about coffee. How could I NOT blog this paper!?

Freedman et al. "Association of coffee drinking with total and cause-specific mortality" NJEM, 2012.

From some of the coverage I've read of this study, you'd think that all you had to do to live happily til 100 is drink MOAR COFFEE. Far be it from me to prevent the intake of one of my favorite beverages, but really...it's just not that simple. And I was very pleased by a few pieces of coverage (like this one) that went into the caveats of the study. Because if it seems as simple as "do this one thing and live longer!"...well it's probably not true.

So what was this study? It's a study taken from a large set of data: the AARP Diet and Health study. This is older adults, 50-71. The authors excluded people who were already obese, had diabetes, heart disease, or cancer. They looked at the data in the study concerning how much coffee people drank, and whether it was caffeinated or decaf.

During the time of the data collection (1995-2008), of the total 402,260 people, 52,515 of them died. At first blush, the risk of death (comparing the people who died to the people who didn't and their demographics) was higher among the coffee drinkers.

But when you break it down, a large number of the heavy coffee drinkers (more than 2 cups/day) were also smokers, which is a very high risk of death in and of itself. When you controlled for the smokers, the authors got the OPPOSITE effect, this time coffee drinking (more than 2 cups per day), decreased the risk of mortality by 10% in males and 15% in females.

Keep in mind there that "risk" is risk in the epidemiological sense. So the study found that you are less likely to die (by a very little bit, 10% is not a lot) if you are an older adult if you drink coffee (caffeinated vs decaf did not make a difference).

When they broke it down by causes of death, they found that mortality risk was decreased in coffee drinkers for most causes: accidental death or injury (more alert and less car accidents?), heart disease, stroke, diabetes, and infections. The only exception was cancer.

So does this mean that we should all be grabbing coffee to extend our lives? Honestly, probably not. Coffee drinking was also associated with a number of other unhealthy habits, not just smoking. Coffee drinkers eat fewer vegetables, exercise less, consume more calories, drank more alcohol, took fewer vitamins, and ate more red meat. Downing a few more cups of coffee isn't going to make up for other bad habits if you have them. And of course, this is a study in humans, and humans are full of variables. There are lots of other things.

Things this study did NOT take into account:
1) How long people had been drinking coffee for vs when they died
2) They took measures of diet but did not control for it, they didn't compare with similar caloric intakes.
3) Meausures of other health outcomes OTHER THAN diabetes, obesity, cancer, etc. 4) They never asked about blood pressure or cholesterol
5) Adjusting for levels of exercise
6) They compared caffeinated vs decaf but only if you had one or the other "more than 50% of the time"

While they took measures of all these things, they only corrected for the smoking. And adjustments for variables, though helpful, will never give you the real picture. And of course, there are two big issues aside from all the little ones.

A: correlation is not causation. People with chronic disease, for example, are often told to avoid caffeine and stop drinking coffee. And in general, it's impossible to prove a cause here, what we have instead is an association. That's a good start, but it doesn't prove...

B: What the mechanism is. What's going on? Coffee is an amalgamation of a hundreds of different chemicals, far more than caffeine alone. I don't think you could figure this out from a human study, you'd have to break down the chemicals and test the unknown ones against various combinations.

So what CAN we tell from this? Well, so far it appears that coffee doesn't increase the risk of death. So that's a start. And should you drink coffee because you like it? Sure! But should you screw up your nose and start chugging coffee and hope to live to 100? Probably not yet.

Freedman, N., Park, Y., Abnet, C., Hollenbeck, A., & Sinha, R. (2012). Association of Coffee Drinking with Total and Cause-Specific Mortality New England Journal of Medicine, 366 (20), 1891-1904 DOI: 10.1056/NEJMoa1112010

9 responses so far

  • gerty-z says:

    MOAR COFFEE!!!! Imma live forever....or not. :)

    Great post, Sci. Looking forward to hearing you on Skeptically Speaking!

  • Stephen says:

    And what about the controls? Were they Mt. Dew addicts? Coffee has fewer calories.

    I heard this recently. Good news: animal model research (worms, mice, up to monkeys) shows that a new diet extends life by 30%, delays dementia diseases like alzheimers and parkinsons. Bad news: you have to fast every other day.

    Maybe it would only seem longer.

    • gerty-z says:

      If you look at the study that showed caloric restriction works in primates, you will find that almost 2/3 of the deaths from those animals were censored as being "not age related". If you include all the data, there was actually a DECREASE in lifespan in the CR animals.

  • Sunfell says:

    I drink coffee. But I do not smoke. I also exercise, eat carefully, drink wine in moderation, enjoy dark chocolate, occasionally indulge in a big fat beef steak, watch TV, mess around on the computer, mow grass without a face mask, kiss my cats (and let them sleep with me), and enjoy life. I stay out of fast food restaurants, avoid soda and fried foods, and won't eat anything that my ancient ancestors would not recognize as edible.

    I might get run over by a bus tomorrow, but darn it, I'll die relatively content.

  • rob says:

    Well. The study seems to be a bit skewed. Considering the fact not everyone drinks coffee and if caffine is the trigger that this study was looking after the most then.we only have to be looking at those who consume the caffine. But as I read. The report. Said they would have to break down the components in the coffee to find out what all coffee beans may have that would be a contributing factor of longivity. On mortality. In men and women. As we already know women naturaly live longer than most men do. So we would have to weigh the consumtion levels of both men and women over 50. And see what lifestyle and health care they receive all these things factor in to how much or how less a little extra caffine would have a effect on the mortality of the subject group. Well in saying all that. I think the focus needed to be on what benifit coffee offers to those over 50. Thanks

  • Jim Thomerson says:

    I've been told there is caffeine in other things than coffee, but I don't believe it. My wife told me of a group of coffee addicts. The person in charge accidentally provided decaf, and thought no one would notice. The group came down with headaches, respiratory problems, etc. She went out and got real coffee and all was well.

    Anyway, I like the research results. If nothing else, the placebo effect will help me live long.

  • [...] And from Jeremy: Will you live longer if you order an extra shot in that latte?¬†Probably not. [...]

  • Macrobe says:

    Nice to see other scientists with ability to think (and read) critically. :)

  • [...] This week, we’re looking at what the evidence has to say about common claims about diet, exercise, weight loss and other hot health topics. We’re joined by health law professor Timothy Caulfield, to talk about his book The Cure for Everything! Untangling the Twisted Messages About Health, Fitness and Happiness.¬†And researcher and science blogger Scicurious looks at a new study of coffee consumption, and the effect it may – or may not – have on life expectancy. [...]

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