The use of hormone replacement therapy in postmenopausal women may not provide protection against heart disease, according to a follow-up to a landmark study.

The findings, published in  JAMA Internal Medicine, are a result of another look at a landmark study that began in 1991 and examined 162,000 postmenopausal women. The women were separated into groups with some taking a placebo, some taking estrogen and some taking an estrogen and progestin combination. The original study examined the long held belief that the therapy was effective not only in treating menopausal symptoms, but also conditions such as heart disease.

Each woman was tracked for five to seven years and when the findings of the study were release in 2002, it was discovered that women taking estrogen and progestin had higher risks of heart disease and breast cancer than those taking the placebo. Those results prompted millions of women to stop taking hormones and, according to CBS News, today only 10 percent of women use hormone replacement in menopause.

The follow-up study, released on Oct. 2, shows that long-term use of hormones can increase a postmenopausal woman’s risk of heart disease and breast cancer. The use of a combination of estrogen and progestin carried more risks than taking just estrogen. The new research shows that a combination of therapies significantly increased risk of breast cancer, accounting for nine cases in every 10,000 women. There were also more strokes and blood clots.

“This study underscores that estrogen is not useful in the prevention of cardiovascular disease,” says Dr. Gina Lundberg, a preventive cardiologist with Emory Healthcare and a national spokesperson for the American Heart Association.

The study also showed that negative effects from the therapy were felt most strongly in older women.

“In general, I advise women to avoid hormone replacement when possible and only take the lowest dose necessary when needed for symptomatic menopausal relief. And I encourage all women to start weaning off estrogen starting at age 59 and be completely off by age 65,” she says.

Even with this research, there may still be some healthy effects of the therapy for women with severe menopausal symptoms.

Lundberg says, “Women should avoid hormone replacement for prevention of heart disease. However, when estrogen is needed for significant menopausal symptoms, the lowest dose for the shortest amount of time is generally safe.”

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