Lessons from history #13: Hormone replacement therapy

Hormone replacement therapy (HRT) for post-menopausal women was thought to decrease the chance of cardiovascular problems like heart attack and stroke. This ‘made sense’ because the risk of cardiovascular disease in women rose sharply after menopause, indicating that female hormones had a protective effect. Many large observational studies supported this belief, and HRT was widely prescribed in the 1980s and 1990s. Later evidence from large, placebo controlled, randomised trials failed to show any cardiovascular benefit. Again, observational evidence was shown to overestimate the effectiveness of a common medical treatment and again, practice became established before the definitive trials were done.

Surgery for high blood pressure

The most recent casualty of the sham surgery trial, adding to the list of operations that looked good and had good results until put to the leased biased test, is a procedure called renal denervation (cutting the nerves to the kidney). Years of good results showing that this procedure lowered blood pressure are now met with a blinded sham-controlled trial that showed no significant benefit over placebo.