New findings on HRT and heart risk

[Posted: Wed 01/10/2008 by Deborah Condon]

It is not what you take but the way that you take it that can produce different results in women who take hormone replacement therapy (HRT), the results of a new study indicate.

This study is the largest to look at the effects of HRT since a UK Women’s Health Initiative (WHI) trial was stopped early in 2002 after finding that HRT increased the risk of women developing breast cancer and heart problems.

Since those findings were released, it has become apparent that the WHI study group was not completely representative of women taking HRT and was characterised by a high incidence of several important risk factors which would be considered unusual in younger women entering the menopause. For example, the average age of women in the study was 63, a decade older than the age most women begin HRT.

Nonetheless, the findings caused widespread anxiety among women taking HRT at the time.

This latest study looked at almost 700,000 healthy Danish women, aged 51-69. Their progress was monitored over the period 1995-2001. It found that overall, no increased risk of heart attack was found in current users of HRT compared to women who had never taken it.

However, it did find that in younger women (aged 51-54) who were taking HRT during the period of the study, their risk of suffering a heart attack was 24% more likely than in women who had never taken HRT. In addition, in younger women there was an increasing risk with longer duration of HRT, which was not seen in the older age groups.

The study also found that the type of HRT and the way that women took it made a difference to the risk of heart attack.

Continuous HRT (a continuous combination of oestrogen and progesterone) carried a 35% increased risk of heart attack compared with women who had never used HRT. But if HRT was taken on a cyclical basis (oestrogen, followed by a combination of oestrogen and progesterone), there was a tendency for these women to have a reduced risk of heart attack compared to women who had never used HRT.

Furthermore, if the method of taking the oestrogen was via a patch or gel on the skin or in the vagina, the risk of heart attack was reduced by more than a third.

“Our finding of lower risk with a cyclic combined regimen, which gives monthly bleeding, than with continuous combined oestrogen/progesterone therapy, which does not cause bleeding, is potentially of great clinical importance. Also, the decreased risk of heart attack with vaginal treatment is a very interesting finding that has not been tested before in large scale observational studies,” said lead researcher, Dr Ellen Løkkegaard.

She said that the findings do not change indication and duration recommendations for HRT. However they do indicate that if a woman is to use HRT, ‘then a cyclic combined regimen should be preferred and that application via the skin or the vagina is associated with a decreased risk of myocardial infarction (heart attack)’.

“This study is the first, big observational study that addresses the influence of various regimens, doses and routes of administration. In this ‘post randomised era’ where randomised studies on HRT are not easily performed, it provides important new information,” Dr Løkkegaard added.

Details of these findings are published in the European Heart Journal.