Conclusive studies have now proven definitively that the most commonly used forms of hormone therapy do not prevent the progression of heart disease in women who have already been diagnosed with the condition, nor do these hormones prevent the onset of heart disease in healthy women.  In fact, healthy women are more likely to experience heart attacks, as well as stroke and blood clots if they take the estrogen/progestin combination Prempro. Estrogen alone also causes strokes and blood clots.
Women's Health Initiative
The most important information about hormones' effect on heart disease comes from the Women's Health Initiative. This large, government-funded trial has been studying the effects of hormone therapy for several years by randomizing healthy women to take either the actual drug or a look-alike placebo with no active ingredients. Women taking either Premarin or Prempro had an increased risk of heart attack, blood clots, and stroke in the first two years of the study. These risks did not recede with longer use of Prempro. Women using Premarin continued to have a higher risk of stroke and blood clots throughout the study.
In 2002, the Women’s Health Initiative was abruptly halted due to the finding that study participants who took hormone therapy had increased the risk of negative health events. Recently, however, some scientists have begun to speculate that initiating hormone therapy early in menopause is the key to cardiovascular protection. Although there is insufficient scientific evidence to support these claims, many have insisted on promoting these guesses in the popular media, misleading women once again about the benefits and risks of hormone therapy. Earlier this year, a series of journal articles went as far as to speculate that hormone therapy can actually be cardioprotective if taken during early menopause! This fact sheet will help you distinguish between proven scientific facts and conjectured hypotheses regarding hormone therapy and cardiovascular disease.
Window of Opportunity Theory
In women 10 years beyond the menopausal transition choose to take hormones for menopausal symptoms, it should be for the shortest period of time at the lowest possible dose. However, some scientists have recently speculated that starting prescription hormones during the menopausal transition (either before, or within a year or two after the last menstrual period) could prevent the development of heart disease, and subsequently cardiac events such as heart attacks. This theory has been called the "Unified Hypothesis" or the "Window of Opportunity Theory" of hormone therapy.
"Window of Opportunity" theorists propose that the ability of estrogen to lower coronary atherosclerosis means that it can be prescribed to prevent heart disease. They suggest that hormone therapy may have a beneficial effect on heart health if it is initiated early in menopause when a woman’s arteries are still likely to be relatively healthy. They concede that hormone therapy may have a harmful effect if started in late menopause when advanced atherosclerosis may be present.4 However, it is essential that patients and physicians understand that this opinion is only a hypothesis and has not been supported by any randomized controlled clinical trials. The WHI Investigators who formalized this hypothesis actually state in a medical journal article that this theory has not been tested: "as yet there has been no clinical trial that has tested the unified hypothesis directly." Moreover, the rationale behind this idea has fundamental flaws.
According to the "Window of Opportunity" line of reasoning, we should be questioning not the age at which hormone therapy is initiated, but rather the arterial health of the woman because this is what, so these theorists say, decides the effect of hormone therapy on a woman’s cardiovascular system. Due to the ongoing global obesity epidemic, atherosclerosis is occurring at younger ages. A younger woman early in menopause who is overweight is likely to have advanced atherosclerosis, in which case – according to the rationale behind the "Window of Opportunity" hypothesis – hormone therapy cannot be deemed beneficial. Thus, the idea that certain age, a numeric figure, can be the deciding factor as to whether hormone therapy will have beneficial or adverse effects for all women is imprecise. A more sensible implication of this hypothesis is that clinicians can be reassured about cardiac risks when considering short-term use of hormone therapy for menopausal symptom relief in such women.
Women have a right to know this critical point – that currently there is no scientific evidence to support the "Window of Opportunity" theory as a clinical recommendation for women’s heart health. To date, the most reliable evidence on hormone therapy use by women in the early stages of menopause is from the Women’s Health Initiative. Although critics often state that the WHI was a clinical trial of "older" women in their 60’s & 70’s, over 12 percent of WHI participants were aged 50 to 54 at baseline (n = 2,029), making it the largest randomized clinical trial of hormone therapy ever conducted in this age group. Statistical analyses of the WHI data did not indicate significant differences by age in the effect of estrogen and progesterone (E+P) on the risk of heart disease; in other words, younger WHI participants who took E+P were at no less risk nor were they more protected from heart disease compared to older participants. Another recent analysis of the WHI data on women who had undergone hysterectomy also found that estrogen alone did not provide significant cardiovascular protection in women aged 50-59.
Women who are taking Premarin or Prempro to prevent heart disease should stop. It does not work, and it actually increases the risk of heart attack, stroke, and blood clots. Women who are taking other brands of hormone therapy to prevent heart disease should also consider stopping. Although other types of hormone therapy are not as well studied as Premarin and Prempro, it is clear that no hormone therapy has been proven to prevent heart disease in healthy women and none is without risk.
The American Heart Association and a National Institutes of Health Consensus Panel have both clearly stated that hormone therapy should NOT be used as a protective agent against cardiovascular disease. A health care practitioner who prescribes hormones as a protective measure against heart disease for younger women in their forties or fifties is making an irresponsible clinical decision without sufficient scientific evidence, and may actually be endangering the health of the patient.
Menopause doesn't cause heart disease
Ultimately, age, not menopause, is the biggest risk factor for heart disease. Women who go through natural menopause in their early forties are no more likely to experience heart disease than are women who continue menstruating into their 50s. Heart disease rates increase slowly during middle age and then begin to rise rapidly after women reach their mid-sixties. By age 75, women have heart attacks nearly three times more often than 65 years old women and heart disease becomes the leading cause of death of all women.
However, some scientists have recently speculated that starting prescription hormones during the menopausal transition (either before, or within a year or two after the last menstrual period) could prevent the development of heart disease, and subsequently cardiac events such as heart attacks. This theory has been called the "Unified Hypothesis" or the "Window of Opportunity Theory" of hormone therapy.
In women who are at least 10 years beyond the menopausal transition, scientists agree that hormone therapy increases the risk of heart disease; if women in this stage of life choose to take hormones for menopausal symptoms, it should be for the shortest period of time at the lowest possible dose.
How to reduce the risk of heart disease
Everyone can reduce their risk of developing heart disease, even those with a strong family history of heart disease. The leading risk factors for heart disease are smoking, diabetes, high blood pressure, high cholesterol levels, abdominal obesity, and physical inactivity. Good studies have shown that changing health habits can reduce or eliminate each of these risk factors, resulting in a much lower rate of heart disease.
Changes that can help:
- Smoking: If you smoke, make plans to stop. Treatments using person-to-person contact are especially effective and should include social support and problem-solving skills.
- Diabetes: Physical activity and healthy eating habits are more effective at preventing diabetes than is medication. A recent large study found that 30 minutes of activity five days a week, and a 7 percent weight loss were enough to lower the risk of developing diabetes by more than 50 percent.
- High blood pressure: Changing eating habits to increase fruits, vegetables, and whole grains and decrease fat, meat, and sweets can lower blood pressure and reduce the risk of heart attack and stroke. In a controlled study, this diet (called DASH) lowered blood pressure just as well as taking medication. The DASH diet seems to be especially effective in African Americans.
- High cholesterol: The TLC diet (Therapeutic Lifestyle Changes), which emphasizes moderately low-fat overall eating habits and low intake of dietary cholesterol, has been shown to reduce cholesterol levels.
- Physical inactivity: Some studies have shown this to be a stronger predictor of heart disease than obesity. Although more exercise is better, women can reduce their risk of heart disease with 30 minutes a day of moderate exercise.
- Abdominal obesity: Losing 10 percent of the total weight (for example, 16 pounds for a 160-pound woman) has been shown to reduce the risk of heart disease. Many people can accomplish a 10 percent weight loss through increased activity and reduce calorie intake.
All of these changes are potentially attainable by women concerned about heart disease. However, many women face barriers to these changes. Issues such as the demands of family and work, concerns about personal safety, and costs can stand between women and exercise, smoking cessation, and diets rich in fresh produce. The NWHN supports policy changes to reduce these barriers.
In the meantime, for people who cannot incorporate risk reduction strategies into their lives, or who haven't gotten adequate results, some medications have been shown to reduce the risk of heart disease in women, such as low-dose aspirin and to treat risk factors for heart disease such as diabetes, high blood pressure, and smoking.
The American Heart Association has a fact sheet, "Q & A About Hormone Replacement Therapy," and information about prevention and effective treatments for heart disease.1-800-242-2871, or http://www.americanheart.org. The National Heart Lung and Blood Institute has information on the DASH and TLC eating plans. Write to NHLBI, PO Box 30105, Bethesda, MD 20824 or http://www.nhlbi.nih.gov.
-  Hulley S, Grady D, Bush T et al., "Randomized Trial of Estrogen Plus Progestin for Secondary Prevention of Coronary Heart Disease in Postmenopausal Women," JAMA 1998; 280: 605-613.
-  Rossouw J, Anderson G, Prentince R et al., "Risks and Benefits of Estrogen Plus Progestin in Healthy Postmenopausal Women," JAMA 2002; 288: 321-333.
-  The Women's Health Initiative Steering Committee, "Effects of conjugated equine estrogen in postmenopausal women with hysterectomy," JAMA 2004; 291: 1701-1712.