MedWire News: Postmenopausal women who take hormone replacement therapy may be increasing their risk of suffering a stroke, results of a US study suggest.

"Many controversies remain regarding the risks and benefits of postmenopausal hormone therapy. In particular, there are relatively limited data regarding the effects of hormone use on stroke," explain Dr Francine Grodstein, from Brigham and Women's Hospital in Boston, Massachusetts, and team.

To investigate further, the researchers studied data on 121,700 women who participated in a long-term health study.

All the women provided information on their use of hormone replacement therapy, and their medical records were used to identify those who had suffered a stroke over the course of the 30-year study.

Overall, women who had used oestrogen only hormone replacement therapy were 39% more likely to suffer a stroke and those who had used oestrogen plus progestin were 27% more likely to experience a stroke than other women.

The risk of stroke also appeared to increase with increasing doses of oestrogen.

However, the researchers found no clear evidence of an increased risk of stroke among women younger than 55 years who had taken hormone replacement therapy for fewer than 5 years. But the researchers explain that this finding may be due to the small number of cases in this category.

Writing in the Archives of Internal Medicine, Dr Grodstein and team conclude: "Our findings in the Nurses' Health Study indicate that hormone therapy is associated with an increased risk of stroke, regardless of the hormone regimen or the timing of hormone therapy initiation.

"However, in younger women, who are at lower absolute risk of stroke, the attributable risk of stroke owing to hormone use is modest, and our data suggest that risk might be further minimised by lower doses and shorter duration of treatment."