Oestrogen-based hormone therapy does not increase the risk of developing coronary heart disease in women aged 50-79 years, according to a new analysis of data from the Women’s Health Initiative study, published in the Archives of Internal Medicine.

But a sub-analysis of the trial also revealed that ostrogen therapy may also protect younger menopausal women - aged 50-59 - from heart disease, after a 34% lower risk for the combined endpoint of heart attack, coronary death, coronary revascularization and confirmed angina was found amongst this group.

"This new information is important for many women taking or considering postmenopausal oestrogen therapy to relieve the symptoms of menopause and/or to prevent osteoporosis," says Lila Nachtigall, from the New York University School of Medicine. "These findings, coupled with other recent data, support the emerging belief that the age of the woman and time since menopause should be considered when assessing the overall benefit and risk of hormone therapy."

The WHI was a large-scale study sponsored by the National Institutes of Health, designed to assess hormone therapy, dietary modification, calcium and vitamin D as preventative therapies for post-menopausal women. The initiative was fired into the media spotlight in 2002 after an analysis of data indicated a higher risk of heart attack, stroke, breast cancer and other serious conditions with combined oestrogen plus progestin hormone replacement therapy, causing thousands of women to bin their drugs in favour of alternative therapies.

Consequently, experts were quick to caution that hormone replacement therapy should only be given to women in the lowest doses and for the shortest time period possible, causing sales of Wyeth's Premarin (oestrogen) and Prempro, (oestrogen and progestin) to plummet.

But this latest analysis was of the oestrogen-alone sub-study, which evaluated 0.625g Wyeth’s Premarin in 10,738 women age 50 to 79 years (mean age 63 years) who had previously had a hysterectomy. As Ginger Constantine, Vice President, Women's Health Care and Bone Repair at Wyeth Pharmaceuticals, remarked: "This new information may be reassuring to millions of women who currently take, or are appropriate candidates for, oestrogen-alone therapy." However, she was also careful to point out that, despite the indication that the therapy may offer cardiac benefits in the 50-59 age group, “oestrogen therapy, with or without a progestin, should not be used for the prevention of coronary heart disease."