The keyword here is older. In women, heart attacks and heart disease usually begin at an older age than in men. And this is the cause of estrogen.
Scientists have long known that this female hormone protects women from heart disease. (Interestingly, when researchers, experimenting, gave estrogen to men, they found that estrogen doesn’t have a protective effect on men.) When the amount of hormone produced begins to decrease and then stops in menopause, the risk of developing heart disease increases. But researchers also found that estrogen replacement therapy greatly reduces the risk. According to Trudy L. Bush, Ph.D., associate professor of epidemiology at the Faculty of Hygiene and Public Health at Johns Hopkins University in Baltimore, women who use estrogen replacement therapy are twice as likely to suffer from heart attacks as compared to those who do not take estrogen.
Experts believe that estrogen helps to increase the level of "good" HDL-cholesterol (with high-density alpha-lipoproteins), which "protects" the heart. They found that women taking estrogen had higher levels of "good" cholesterol and lower levels of "bad" LDL-cholesterol (with low density alphalipoproteins). “It’s high levels of 'bad' LDL-cholesterol that cause blood vessels and heart to form plaques that clog up blood vessels,” explains Dr. Bush. But high levels of "good" cholesterol protect the heart and blood vessels from plaque formation. "
Of course, estrogen replacement therapy also has contraindications. For example, it is believed to increase the risk of certain types of cancer.