Wednesday, March 03, 2010

Coffee and the Heart - Good or Bad?

This week, it seems to be good:
“People who are moderate coffee drinkers can be reassured that they are not doing harm because of their coffee drinking,” said Arthur Klatsky, the study’s lead investigator and a cardiologist at Kaiser’s Division of Research.
These "surprising" data are to be presented at the AHA meeting March 5th. (You'll have to wait until then to get the REAL scoop, it seems.)

But a quick Google search on Dr. Klatsky's earlier studies using the same questionaire database shows the problems with using questionaire data to make such sweeping conclusions. Take, for instance, these findings from 1973:
"Coffee drinking is not an established risk factor for myocardial infarction."
And yet a bit later, in 1990, there's a flip flop:
Because of conflicting evidence about the relation of coffee use to coronary artery disease, the authors conducted a new cohort study of hospitalizations among 101,774 white persons and black persons admitted to Kaiser Permanente hospitals in northern California in 1978–1986. In analyses controlled for eight covariates, use of coffee was associated with higher risk of myocardial infarction (p=0.0002). (By the way, British researchers failed to find a similar correlation in instant coffee drinkers)
So what, really, do these data from the Kaiser questionaire data regarding heavy coffee consumption and the heart say?

What they say is:
  1. Questionaire data crunched to suggest correlations are insufficient to mean causation, irrespective of how the media parses it.

  2. Questionaire data are subject to significant sampling and reporting biases.

  3. Rehashing the same old questionaires using the same samples with newer data can dramatically alter prior findings.

  4. Researchers are getting paid way too much to keep rehashing the same data for large health systems.

  5. On the lighter side, college undergrads and medical students should note that they could use these types of questionaire data to justify significant caffeine consumption along with alcohol to protect themselves from developing cirrhosis.
* Sigh *


h/t: The Happy Hospitalist for the story idea.


Unknown said...

The “coffee is protective” conclusion is fishy.

Recalling work done about twenty-five years ago: Working at a pharmaceutical company on a cardioprotective drug lead. We would open up a pig, so we could defibrillate it as needed, and then injected theophylline (which mimics caffeine) IV. We caused fibrillation by exciting the heart with a fixed current during the t-wave. The more theophylline on board the pig, the lower the threshold for inducing fibrillation. Always.
The drug candidate worked but had other “issues”.

My guess is that people who drink four cups of coffee daily have already “self selected”, and are those who are much less prone to caffeine-induced cardiac disturbances.

Bart J. Zoltan

Marco said...

Reminds me of a friend who, after having a particularly strong espresso, said "Wow, I think I'll go vacuum a freeway."

The Happy Hospitalist said...

thanks doc


Gina and the Gang said...

Thank goodness! Because those of us who have young kids with Congenital Heart Defects put coffee in it's own food group to stay alive!!