For women with heart disease, HRT can temporarily raise the risk of heart attack and death.

An earlier trial called the Heart and Estrogen/progestin Replacement Study had shown that among women with heart disease, taking oral estrogen plus progestin elevated the risk of recurrent heart problems in the first year of use.

Researchers in one of the new studies analyzed 20 years' worth of data on nearly 2,500 women in another large US trial.

Overall, the women -- who all had established heart disease -- saw their risk for heart attack and death go up 25% in their first year on HRT, compared with those who never used hormones.

And there was no apparent difference based on type of HRT, according to rthe Harvard researchers.

The second study echoed these results. Investigators at Duke University found that women who started HRT after having a heart attack were 44% more likely than those who never used HRT to have another heart attack or die in the following year.

The study, reported in the July issue of the Journal of the American College of Cardiology (JACC), involved nearly 1,900 postmenopausal women who had suffered heart attacks.

Why HRT presents a temporary risk to women with heart disease is unclear, the researchers note. Grodstein's team points out that there is evidence HRT increases levels of C-reactive protein, an inflammatory substance linked to heart disease. However, they add, heart disease patients on HRT have been shown to have improved cholesterol counts and blood vessel function.

Annals of Internal Medicine July 2001;135:1-8;
Journal of the American College of Cardiology July 2001;38:1-7, 8-9