[Adverse cardiovascular effects of postmenopausal hormone replacement therapy]

The views on the effects of postmenopausal hormone-replacement therapy (HRT) on cardiovascular disease have moved from one end of the spectrum to the other over the past decades. The presumed beneficial effects of HRT on arterial cardiovascular disease were based on observational findings and have led to the widespread use of these agents. However, recent large-scale randomised, placebo-controlled trials have demonstrated that HRT in women with a history of arterial diseases initially increases the risk of recurrent disease, while offering no benefit in the long term. Healthy postmenopausal women on HRT have an increased risk of arterial cardiovascular events compared with those taking placebo (relative risk 1.29; 95% CI: 1.02-1.63). Finally, the risk of venous thrombosis and pulmonary embolism is increased with the use of HRT. These results demonstrate that bias and confounding can play an important role in observational research and underscore the importance of randomised, placebo-controlled trials when studying the efficacy of drugs.