Reporting in today's issue of the American Journal of Epidemiology, researchers from University Medical Center, Utrecht, the Netherlands, found the older a woman is when she beginsmenopause, the less likely she is to die from cardiovascular disease. The reason, they theorize, is she holds onto her natural estrogen supply longer.
Natural estrogen is made in both fat cells and the ovaries. Because menopause is a time when ovarian function declines, the authors suggest the protective supply is likely to be ovarian in origin.New York City cardiologist Dr. Dan Fisher says that while the findings are far from definitive, they are tantalizing.
"Perhaps it's showing us that we should not give up on estrogen as a possible way to protect women from heart disease, even though the latest studies indicate that, so far, we have not been able to duplicate that protection with the use of synthetic hormone therapy," says Fisher.
Last July, the American Heart Association issued an advisory suggesting there wasn't sufficient evidence to warrant the use of hormone replacement therapy (HRT) strictly for the prevention of cardiovascular disease. Then, the recent release of information from the largest study ever of HRT found the therapy may actually increase the risk of cardiovascular disease and death in women.
However, results of the Dutch research show estrogen does appear to have protective effects -- as long as it's made naturally in the body.
The study included 9,450 post-menopausal women from the same area of the Netherlands. When the study began -- in 1975 -- the ages of the women ranged from 35 to 65.
The researchers followed the women for slightly more than 20 years, and documented the rate of heart disease and death from heart disease for each woman in the study.
What they found: Those women who were 52 or older when they entered menopause saw an 18 percent decrease in cardiovascular disease, when compared to women aged 44 or younger.
More specifically, women who experienced 20 or more years of exposure to natural estrogen had what authors called "a statistically significant 20 percent reduction in cardiovascular mortality, when compared to women who had just 13 years of exposure or less."
The study authors conclude that age at menopause is directly linked to cardiovascular disease and mortality -- and that extended estrogen production is the key.
Fisher, however, questions whether it's estrogen alone that should get all the credit.
"It's possible that there is some unknown factor that is linked to natural estrogen production in the body -- something else going on that we have yet to identify that could account for the difference in the rate of heart disease in these women," Fisher says.
For New York gynecologist Dr. Andrei Rebarber, the other factor noted by the researchers -- the age of the women at menopause -- may hold the real clue to understanding the findings.
"It could be that whatever factor is causing a woman to go into menopause at a younger age may be the real reason behind her increased risk of heart disease and death from heart disease," he says. "And that factor may not necessarily be estrogen production."
On the other hand, Rebarber suggests that if estrogen is the protective element, that protection may be more dose-related than thought.
"Perhaps we may find that HRT is able to protect women from heart disease, but that we need to pay more attention to subtleties in dosing. Perhaps the dose that offers protection may be different for each woman," Rebarber says.
Ultimately, the study points up the need for more research to further understand all the factors that place a woman at increased risk for heart disease, he says.
"Maybe its true value is in highlighting how much we still need to learn about women and cardiovascular disease, and the need for more research," Fisher says.
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