Do We Really Know What Makes Us Healthy?

This is a very long piece in today’s Sunday Magazine of the NY Times.

Two excerpts:

This in turn leads to the argument that the fault is with the press, not the epidemiology. “The problem is not in the research but in the way it is interpreted for the public,” as Jerome Kassirer and Marcia Angell, then the editors of The New England Journal of Medicine, explained in a 1994 editorial titled “What Should the Public Believe?” Each study, they explained, is just a “piece of a puzzle” and so the media had to do a better job of communicating the many limitations of any single study and the caveats involved — the foremost, of course, being that “an association between two events is not the same as a cause and effect.”

Stephen Pauker, a professor of medicine at Tufts University and a pioneer in the field of clinical decision making, says, “Epidemiologic studies, like diagnostic tests, are probabilistic statements.” They don’t tell us what the truth is, he says, but they allow both physicians and patients to “estimate the truth” so they can make informed decisions. The question the skeptics will ask, however, is how can anyone judge the value of these studies without taking into account their track record? And if they take into account the track record, suggests Sander Greenland, an epidemiologist at the University of California, Los Angeles, and an author of the textbook “Modern Epidemiology,” then wouldn’t they do just as well if they simply tossed a coin?

As John Bailar, an epidemiologist who is now at the National Academy of Science, once memorably phrased it, “The appropriate question is not whether there are uncertainties about epidemiologic data, rather, it is whether the uncertainties are so great that one cannot draw useful conclusions from the data.”

and

It’s this prescriber effect, combined with what Avorn calls the eager-patient effect, that is one likely explanation for why people who take cholesterol-lowering drugs called statins appear to have a greatly reduced risk of dementia and death from all causes compared with people who don’t take statins. The medication itself is unlikely to be the primary cause in either case, says Avorn, because the observed associations are “so much larger than the effects that have been seen in randomized-clinical trials.”

If we think like physicians, Avorn explains, then we get a plausible explanation: “A physician is not going to take somebody either dying of metastatic cancer or in a persistent vegetative state or with end-stage neurologic disease and say, ‘Let’s get that cholesterol down, Mrs. Jones.’ The consequence of that, multiplied over tens of thousands of physicians, is that many people who end up on statins are a lot healthier than the people to whom these doctors do not give statins. Then add into that the people who come to the doctor and say, ‘My brother-in-law is on this drug,’ or, ‘I saw it in a commercial,’ or, ‘I want to do everything I can to prevent heart disease, can I now have a statin, please?’ Those kinds of patients are very different from the patients who don’t come in. The coup de grâce then comes from the patients who consistently take their medications on an ongoing basis, and who are still taking them two or three years later. Those people are special and unusual and, as we know from clinical trials, even if they’re taking a sugar pill they will have better outcomes.”

The trick to successfully understanding what any association might really mean, Avorn adds, is “being clever.” “The whole point of science is self-doubt,” he says, “and asking could there be another explanation for what we’re seeing.”

You will find this long, somewhat difficult article worthwhile.