The HRT-Prevents-Heart-Disease Doctrine — a 16,608-Woman Trial Halted for Causing the Heart Attacks

On 8 July 2002, the writing group of the Women’s Health Initiative announced that it had stopped the estrogen-plus-progestin arm of its trial roughly three years early, after a mean of 5.2 years, because the combined hormone regimen taken by 16,608 healthy postmenopausal women had increased coronary heart disease rather than preventing it — a hazard ratio of 1.29, alongside elevated stroke (1.41), breast cancer (1.26), and blood clots (roughly doubled). The promise and the reality had been inverted: for nearly two decades, conjugated equine estrogen had been prescribed to protect women’s hearts on the strength of observational data, and the first large randomized test of that promise in healthy women found the hearts were marginally worse off. The gap between the doctrine and the data would be counted in millions of prescriptions written for a benefit that did not exist.

The cardioprotection belief was not a fringe idea. It was mainstream preventive cardiology, taught in medical schools and embedded in clinical guidance, resting on some 40 to 50 observational studies — most prominently the Nurses’ Health Study, which reported current HRT users with coronary heart disease risk reduced by roughly 40 percent (relative risk near 0.61). Conjugated equine estrogen, sold by Wyeth as Premarin since 1942 and as the estrogen-progestin combination Prempro from 1995, exceeded two billion dollars in sales in 2001. The molecules were never recalled; they remain licensed today for menopausal symptoms. What collapsed in July 2002 was the theory attached to them — the claim that they prevented heart disease — displaced not by a scandal or a fraud but by the single most decisive instrument in clinical medicine: a large, randomized, placebo-controlled trial pointed directly at the question the observational data had only ever circled.

The reversal had been foreshadowed. In 1998, the HERS trial — 2,763 women who already had coronary disease, randomized to estrogen-plus-progestin or placebo — had found no overall benefit for secondary prevention, and a 50 percent excess of cardiac events in the first year. The field absorbed HERS as a special case (sick women, late timing) and held to the primary-prevention promise. WHI tested that promise in healthy women, and it failed too. The market answered within months: combined-therapy prescriptions fell by roughly two-thirds within a year, and in 2003 the US Food and Drug Administration imposed a class-wide boxed warning.

This dossier files “Overturned” entry TH-006 as the archetype of a different failure than fraud. No one falsified data. A generation of physicians inferred causation from correlation in self-selected, healthier-than-average hormone users, and only a randomized trial could break the spell — long after the prescription pads had done their work.