The New England Journal of Medicine has published a sub-group analysis of the Women's Health Initiative. This trial has been reported in the Daily Mail and Daily Express although one report suggested that the trial compared two active treatments.
This analysis examined coronary artery calcification in post-menopausal women aged 50 to 59 years at enrolment. Each patient had undergone hysterectomy and was randomised to hormone replacement therapy (HRT) with conjugated equine oestrogen 0.625mg per day or placebo.
Each participant in the study received HRT or placebo for the duration of the study (average 7.4 years) and approximately one year after stopping treatment underwent a CT scan to measure coronary artery calcium score. The results of the scans were assessed independently without knowledge of the treatment used. Coronary artery calcium score is a surrogate marker and is predictive of future risk of cardiovascular events.
The study found that the average coronary artery calcium score was statistically significantly lower in those patients who had been taking HRT than in those who had taken placebo. Correction for baseline cardiovascular risk did not change the outcome of the study.
The authors of the paper conclude that, "oestrogen has complex biologic effects and may influence the risk of cardiovascular events and other outcomes through multiple pathways". One potential flaw in the study was the fact that treatment had been stopped for a year before the CT scans were performed.
It is already known from the complete WHI studies that combined HRT is not cardioprotective and may increase the risk of cardiovascular disease. The oestrogen only study failed to demonstrate cardiovascular benefits and was stopped early due to an increase risk of stroke
Action: HRT should only be used for menopausal symptom control. HRT (combined and oestrogen only) is not an appropriate intervention for prevention of cardiovascular events.