Hormone therapy is linked to increased stroke risk among women.

Summarized by Susan Aldridge, PhD, medical journalist
May 9, 2008

Summary

A new report from the Nurses Health Study reveals an increased risk of stroke from taking hormone replacement therapy (HRT). Those beginning HRT before, during and after menopause were all affected. The risk, however, was not present for short duration of HRT use and was low in younger women.

Introduction

Hormone replacement therapy (HRT) is used to treat menopausal symptoms like hot flashes and it is effective for this purpose. But some women stay on it for many years and so there has been concern over its long-term impact. And rightly so. For research has shown various health risks associated with HRT, including heart disease and stroke. Researchers at Brigham and Women's Hospital, who have been associated for many years with the Women's Health Study, set out to find out more about the stroke risk associated with HRT. For women on HRT are a diverse group. Some start HRT before menopause, some during and some after. They stay on therapy for varying lengths of time and also they may take estrogen alone, or estrogen plus progestin. It is important for a women contemplating, or already on, HRT to know how the stroke risk will affect her as an individual.

The Nurses Health Study began in 1976, when 121,700 female nurses aged 30 to 55 supplied information about HRT use as well as heart disease diagnoses and related risk factors. In 1980, a dietary and exercise component was added to the investigation. The women are followed up regularly and the study is one of the most authoritative resources we have on women's health.

What was done

The researchers identified first occurrences of nonfatal and fatal stroke occurring between 1976 and 2004. This data was correlated with that on HRT use, recording facts such as duration of use and time of starting relative to menopause onset.

What was found

Compared with women who had never used HRT, those currently on HRT had an increased risk of stroke. This was 39 percent greater for those on estrogen and 27 percent for those on combined estrogen plus progestin. The increased risk applied to women starting HRT at a young age, near the menopause, or even ten years after the menopause. Thus, timing of HRT does not affect the increased stroke risk. But taking HRT for five years or less, to get over symptoms of menopause, at a relatively young age, does not increase stroke risk.

For women aged between 50 and 54, the increased risk of stroke amounted to two extra cases per year per 10,000 women on HRT. There was also a relationship between dose of estrogen and stroke - the higher the dose, the greater the risk.

What this study means

This new research is useful for women and their doctors trying to make an informed choice on HRT. Menopausal symptoms can make life a misery if they are severe. HRT can help, but a woman may have to accept an increased risk of longer-term, and more serious, health problems. Stroke is a devastating and disabling condition, so it is a matter of weighing up the risks and benefits of HRT. The researchers conclude that shorter courses and lower doses of HRT may decrease the risk of stroke, while still offering the benefit in terms of relieving menopausal symptoms.

Source

• Postmenopausal Hormone Therapy and Stroke SL. Koshman, TL. Charrois,  et al., Archives of Internal Medicine, April 28 2008, vol. 168, pp. 861--866

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