Long after research contradicts common medical practices, patients continue to demand them and physicians continue to deliver.
A 2007 Journal of the American Medical Association paper coauthored by John Ioannidis—a Stanford University medical researcher and statistician who rose to prominence exposing poor-quality medical science—found that it took 10 years for large swaths of the medical community to stop referencing popular practices after their efficacy was unequivocally vanquished by science.
Ideally, findings that suggest a therapy works and those that suggest it does not would receive attention commensurate with their scientific rigor, even in the earliest stages of exploration. But academic journals, scientists, and the media all tend to prefer research that concludes that some exciting new treatment does indeed work.
At the same time, patients and even doctors themselves are sometimes unsure of just how effective common treatments are, or how to appropriately measure and express such things. … “NNT” is an abbreviation for “number needed to treat,” as in: How many patients need to be treated with a drug or procedure for one patient to get the hoped-for benefit? In almost all popular media, the effects of a drug are reported by relative risk reduction. To use a fictional illness, for example, say you hear on the radio that a drug reduces your risk of dying from Hogwart’s disease by 20 percent, which sounds pretty good. Except, that means if 10 in 1,000 people who get Hogwart’s disease normally die from it, and every single patient goes on the drug, eight in 1,000 will die from Hogwart’s disease. So, for every 500 patients who get the drug, one will be spared death by Hogwart’s disease. Hence, the NNT is 500. That might sound fine, but if the drug’s “NNH”—“number needed to harm”—is, say, 20 and the unwanted side effect is severe, then 25 patients suffer serious harm for each one who is saved. Suddenly, the trade-off looks grim.
Historians of public health know that most of the life-expectancy improvements in the last two centuries stem from innovations in sanitation, food storage, quarantines, and so on. The so-called “First Public Health Revolution”—from 1880 to 1920—saw the biggest lifespan increase, predating antibiotics or modern surgery.