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Users of HRT at risk of clots and stroke

But Cochrane review says HRT still remains a valid option for some women significantly troubled by menopausal symptoms

Ingrid Torjesen

Wednesday, 11 March 2015

Hormone replacement therapy does not protect post-menopausal women against cardiovascular disease, and may even cause an increased risk of blood clots and stroke, an analysis* of trials published in the Cochrane Library has found.

The researchers reviewed trials involving more than 40,000 women across the world looking at the effects of using hormone therapy for at least six months. Use of HRT by the women varied from seven months to just over 10 years.

Overall, the results showed no evidence that hormone therapy provides any protective effects against death from any cause, and specifically death from cardiovascular disease, non-fatal heart attacks or angina, either in healthy women or women with pre-existing heart disease. Instead the findings showed a small increased risk of stroke for post-menopausal women.

The researchers also explored what effect the timing of HRT has and found that the harms and benefits of hormone therapy vary according to the age of the woman when they started their treatment. There was some evidence that women who started treatment within the first 10 years of their menopause, when menopausal symptoms are most common, seem to have a small protection against death and heart attacks, and no increased risk of stroke. But even in this group, the risk of deep vein thrombosis (DVT) increased.

Dr Henry Boardman, from the department of cardiovascular medicine at the University of Oxford, said: “The evidence we have provides some support for the so-called ‘Timing Hypothesis’, but we should bear in mind the size of this effect. When we looked at the results according to the age of women, or by how long since their menopause that they started treatment, we found that if 1000 women under 60 years old started hormone therapy we would expect six fewer deaths, eight fewer cases of heart disease and five extra blood clots over about seven years, compared to a 1000 similar women who did not start hormone therapy.”

He added: “This is a complicated health issue, where the same treatment offers benefits in some women, but harms in others.” Hormone therapy remains a valid treatment option for women who are significantly troubled by menopausal symptoms, Dr Boardman said. “However the risks and benefits of such treatment vary according to age and medical history. Discussion with your GP is recommended when considering treatment.”

Dr David Tovey, editor in chief of the Cochrane Library highlighted that the main analysis found no benefit for HRT. As a result, he said: “We need to apply caution to the results from the subgroup analysis. However if true, this apparent benefit in preventing heart disease in younger women should be considered alongside other possible benefits and emerging evidence of harms, including the risk of breast cancer, ovarian cancer, and DVT.”

Professor Dame Valerie Beral, director of the Cancer Epidemiology Unit at the University of Oxford, said: “This is an independent review of the totality of the available evidence about the effect of HRT on the risk of heart attack, stroke and blood clots in women. The authors' conclusion that HRT does not protect against heart disease and increases the risk of stroke and blood clots is consistent with advice given over the last decade by drug regulatory bodies in Europe and in North America. In other words, recent claims by some that HRT might reduce the risk of heart attack are unfounded.”

* Boardman HMP, et al. Hormone therapy for preventing cardiovascular disease in post-menopausal women. Cochrane Database of Systematic  Reviews 2015, Issue 3. Art. No.: CD002229. DOI: 10.1002/14651858.CD002229.pub4.

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