Treatment with a cholesterol-lowering statin can significantly reduce the risk of heart disease and possibly death in postmenopausal women taking hormone replacement therapy (HRT), investigators report in the rapid access issue of Circulation: Journal of the American Heart Association.

Women taking statins had a 21 per cent lower risk of heart attack and death related to heart disease and a 33 per cent lower risk of dying from any cause during four years of treatment, compared to women who did not take statins. Statin therapy was also associated with a 55 per cent lower risk of venous thromboembolism (VTE, blood clots in veins), a potentially life-threatening problem that can occur in women on HRT.

"These data add substantial additional support for use of statins in women with heart disease," says David Herrington, M.D., M.H.S., lead author of the report. "Our results help clarify residual concerns about the true magnitude of statins' benefit in women, because three previous clinical trials had produced somewhat divergent results."

Herrington's team reviewed data from the Heart and Estrogen/progestin Replacement Study (HERS). The primary purpose of HERS was to evaluate the effect of HRT on heart attack and death in 2,763 women with coronary heart disease. The principal finding of HERS showed no overall effect of hormone replacement therapy on coronary risk.

In their reanalysis of HERS data, researchers looked specifically at the outcomes of 1,004 women taking a statin drug when they entered the study, as well as 708 who began statin therapy during the trial. They found that women taking statins at baseline or at any time during the trial had significantly fewer first-time coronary heart disease (CHD) events (heart attack or CHD death) than those who did not take statins.

Women in HERS who took a statin for at least three years had a 26 per cent lower rate of heart attack and coronary death. Statin use for less than three years was associated with a more modest 11 per cent risk reduction, compared to non-statin users. Death from any cause was 30 per cent lower in women who used a statin at any time during the HERS trial.

Statin drugs have a well-established ability to reduce heart disease risk in men, but until recently the effects in women were less clear, says Herrington, a professor of medicine at Wake Forest University in Winston-Salem, N.C. Earlier studies of statin therapy included relatively few women, and the benefits in women varied widely. HERS was unique because of the large number of women available for study. (Subsequent to HERS, a preliminary summary from the large Heart Protection Study reported significant risk reductions for CHD in women taking 40 mg/day of simvastatin.)

Herrington wanted to reexamine the HERS data to clarify the effects of statins on cardiovascular events in women and to examine the combined effects of statins and HRT on heart attack deaths in postmenopausal women.

Mirroring the primary findings of the HERS trial, the statin analysis showed that HRT users who were not taking a statin had an especially high risk for coronary events during the first year of the trial - 75 per cent higher compared to the placebo group. In contrast, women who were on HRT and a statin during the first year of HERS had the same risk of CHD events as the placebo group.

"The data suggest that statins might help diminish the adverse effects of HRT, but the finding needs to be confirmed in other studies," says Herrington.

Some scientists have wondered whether the lack of HRT benefit on coronary risk in HERS was because of increased statin use in the placebo group, Herrington says. To evaluate the impact of increased statin use in the placebo group, the researchers reanalyzed the data after excluding both women who started statin therapy during HERS and women who took statins before and during the trial. After statistically adjusting for an imbalance in statin use between the treatment and placebo groups, they still did not find a benefit for HRT.

"This study shows that increased statin use in the placebo group did not explain the null finding of the HERS trial," says Herrington.