Women with the highest heart disease risk were the most likely to quit taking hormone therapy after it was shown to offer no protection against cardiovascular disease, a new analysis of national data shows.

Dr. Angela Hsu and colleagues from Columbia Presbyterian Medical Center in New York City found that while 28 percent of women with heart disease were taking hormone replacement therapy in 1999-2000, just 8 percent were in 2003-2004. But for low-risk women, the decline was much smaller, from 20 percent to 17 percent over the same time period.

During the early 1990s, Hsu and her team note, hormone therapy was touted as an effective way to reduce heart disease risk in postmenopausal women. But in 2002, researchers halted a huge study of hormone therapy called the Women's Health Initiative after they found hormones actually boosted the risk of heart disease, stroke, and potentially fatal blood clots known as pulmonary embolisms.

After word spread of hormone therapy risks, use dropped sharply, from around 11 million women 45 to 74 years old in 1999-2000 to 6 million by 2003-2004. Hsu and her colleagues hypothesized that women at the greatest risk of heart disease would account for most of this reduction in hormone use.

For women with cardiovascular disease, they found, hormone use dropped by 70 percent, while it fell by nearly 50 percent in women with two or more risk factors for heart disease, such as high blood pressure or diabetes. Among women with one or fewer heart disease risk factors, however, use dropped just 15 percent, which wasn't statistically significant.

The researchers also found the sharpest decline in hormone use among non-Hispanic white women, who had previously been most likely to use hormone replacement. Both non-Hispanic black women and Hispanic women were much less likely to be using hormone replacement therapy than white women in the first place, and for both groups there was no significant reduction in hormone therapy use.

And while use of hormones fell among all educational levels and all income levels, the biggest drop occurred among richer, more educated women.

Despite the declines the researchers observed, they note that 8 percent of women with heart disease and 14 percent of women with two or more heart disease risk factors were still taking hormone replacement therapy in 2003-2004. The researchers note that they have no information on how long these women took hormone replacement therapy, or why it was prescribed. (Short-term use to treat hot flashes and other menopausal symptoms is currently considered safe.)

The findings suggest, the researchers conclude, that women with heart disease or at the highest risk for heart disease were likely getting hormone replacement therapy to reduce heart risks, a therapy that was never proven for this indication and ultimately found to be ineffective.

SOURCE: American Journal of Public Health, December 2009.