Study: Estrogen May Lower Risk of Heart Disease for Women

Taking estrogen supplements can help women prevent heart disease, a new USC study suggests, a discovery that appears to conflict with some earlier findings.

The new study examines healthy women and a slightly different form of the drug and may provide the best indication yet that estrogen replacement therapy may lower the risk of heart attack. The previous studies were in women who had already developed heart disease.

In a study of 220 women presented last week at an American Heart Assn. meeting in New Orleans, Dr. Howard Hodis of USC found that women who took estrogen daily “had a significant reduction in the progression of atherosclerosis, a change that translates into a reduced risk of future cardiovascular events such as heart attacks and stroke.”

In a separate study also presented at the meeting, Canadian researchers found that women are more likely to suffer heart attacks during or after their periods, when estrogen levels are naturally low.

The two studies together seem likely to fuel the debate over the widespread use of hormone replacement therapy.

Atherosclerosis is the accumulation of plaque in the arteries and accounts for more than 1.5 million heart attacks and 600,000 strokes every year in the United States. Heart disease is the No. 1 killer of American women, striking down more women than cancer and all other diseases combined, Hodis said.

The proposed link between estrogen and heart disease grew out of the massive Framingham Heart Study in the 1970s, in which researchers studied residents of the Massachusetts town for several decades. Scientists concluded that 55 seemed to be an important age for women with respect to heart disease. Before that age, they rarely had heart attacks. After that milestone was reached, the incidence of heart attacks rapidly began catching up with the rate for men.

The obvious conclusion was that the change was linked to menopause. Researchers speculated that the higher levels of estrogen circulating in women’s blood before menopause protected them against heart disease.

Several early studies seemed to support that idea and have found a variety of other beneficial effects of hormone replacement therapy--including increasing bone density, lowering cholesterol levels, decreasing the risk of colon cancer, improving skin tone and, perhaps, lowering the risk of Alzheimer’s disease.

But recent, widely publicized studies found little or no benefit from estrogen replacement therapy in women who had already developed atherosclerosis.

Hodis notes, however, that most previous studies have used Premarin, a complex mixture of estrogens isolated from the urine of pregnant mares. In his study, he used only 17-beta-estradiol, the form of estrogen that occurs naturally in women.

Half of the women in the study received 17-beta-estradiol and half received a placebo. Additionally, all women who started the trial with blood levels of low-density lipoprotein--the so-called bad cholesterol--above 160 were placed on cholesterol-lowering medication whether they received estrogen or not.

To follow their progress, Hodis and his colleagues used highly sensitive ultrasonography to measure the thickness of blood vessel walls in the neck, called the intima-media thickness, or IMT, every six months.

The study is not yet completed. But after two years, he told the meeting, women who took no estrogen and no cholesterol-lowering drugs had thicker IMTs--a sign of hardening of the arteries. In contrast, the IMTs of women who took estrogen actually shrank, suggesting a lowered risk of heart attack and stroke.

Women who took both estrogen and the cholesterol-lowering drug, however, showed no more improvement than those who took only estrogen.

Hodis cautioned that the treatment he used is appropriate only for post-menopausal women who have had a hysterectomy because the use of estrogen without the concomitant use of progestin increases the risk of uterine cancer. “Women should consult with their doctors about the potential cancer risk of the therapy,” he said.

His group will soon begin a new study with the same design, but incorporating progestin to better reproduce conventional hormone replacement therapy.

In the second study, pharmacologist Bettina Hamelin and her colleagues at Laval University in Quebec studied 28 pre-menopausal women, ages 35 to 47, who had been admitted to the hospital for a heart attack or serious chest pain. Hamelin told the meeting that 20 of the women had suffered their problems within five days of the beginning of their period, when 17-beta-estradiol levels were at their lowest.

Hamelin cautioned that all of the women had a number of other important risk factors for heart disease, such as smoking and diabetes.