Menopause Found to Have No Effect on Women's Cardio Vascular Disease Risk
September 6, 2011 (Baltimore, Maryland) — The long-held idea that women are protected from heart disease before they go through menopause is probably false, say US researchers; in fact, the new data show that aging alone explains the increasing number of cardiovascular deaths among females as they get older, Dr Dhanajay Vaidya (Johns Hopkins University School of Medicine, Baltimore, MD) and colleagues report in a study published online September 6, 2011 in BMJ .
And the disparity between the sexes--whereby men seem to have higher heart-disease mortality at a younger age than women--is likely explained by acceleration in cardiovascular disease among males, rather than the previously held belief of some protective effect of female hormones, says Vaidya. "Instead of looking for hormones that protect women, we ought to be looking at what is counterprotective in young men.
Instead of looking for hormones that protect women, we ought to be looking at what is counterprotective in young men.
"While it's true that the menopause is a very dramatic biologic event, nothing special happens after the menopause in terms of cardiovascular disease; hormones are fairly irrelevant," Vaidya told heartwire . "We believe the cells of the heart and arteries are aging like every other tissue in the body, and that is why we see more and more heart attacks every year as women age. Aging itself is an adequate explanation, and the arrival of menopause, with its altered hormonal impact, does not seem to play a role."
This is not true for all diseases, however. Vaidya and colleagues found that menopause clearly plays a role in other diseases for women--for example, the rate of breast-cancer mortality decelerates at menopause, probably because of hormonal changes.
Important Implications for Men and Women
The findings emerge from a different way of analyzing mortality data, and there are a couple of implications, says Vaidya. First, they indicate that doctors should not ignore cardiovascular disease, or more important, messages about its prevention, in younger women.
"The things we know about that are causing damage to the heart and arteries are causing damage throughout a woman's life, so even though very few younger women are having heart attacks, the disease accumulation has already started," he comments.
Also, the new research shows that while there appears to be only one process for heart disease in women--which is aging--in men, there is a "two-stage curve," says Vaidya, "a rapid increase in mortality and then a slow increase in mortality later in life. One of the processes is aging, but overlying the process of aging is another process that we don't currently have a biological explanation for in younger men."
Could Differences in Telomere Length Explain Gender Disparities in CVD?
Vaidya explained to heartwire that his team looked at mortality on a log-scale, using data from people born in England, Wales, and the US between 1916 and 1945 and followed over a long period. This differs from the usual way such analyses are done, which is using a simple linear model.
And while others have used the log-scale to examine CVD mortality, they have usually examined only a "snapshot" in time--for example, the mortality of an 80-year old today, says Vaidya. "But there is a hole in this logic, because people who are 80 years old today have had very different life experiences, and so what we have done is look at the whole second half of the 20th century and followed groups of people over time, so the errors that creep in by pooling together people who have different life experiences are no longer there in our analysis."
The team found that, at the time of menopause in each cohort, there were no increases in female mortality rates above and beyond the steady curve that is expected from aging. They also found that the number of women who die each year from heart disease increases exponentially, at roughly 8% per year, and the death rate curve stays steady throughout life, increasing in risk annually.
In contrast, they discovered that the mortality curve for men under the age of 45 actually increases by 30% a year, only to slow after that age to roughly 5% a year, which is similar to the rate throughout the lifetime in women.
The data suggest that something biological may be happening to younger men that is detrimental to the heart. "Instead of looking at menopause, what we should be looking at is what is happening biologically to men over time," Vaidya says. "We don't have an answer. Good research always creates more questions."
However, his team has a theory. The concept of shrinking telomere length could account for some of the gender differences in heart-disease mortality, they suggest. Previous studies have shown that telomere lengths are similar in male and female babies but become significantly shorter in young adult men as compared with young adult women. And at later ages, telomeres shorten at similar rates in men and women.
The authors have no conflicts of interest.
- Vaidya D, Becker DM, Bittner V, et al. Ageing, menopause, and ischaemic heart disease mortality in England, Wales, and the United States: modeling study of national mortality data. BMJ 2011; 343: DOI:10.1136/bmj.d5170. Available at: http://www.bmj.com.
Heartwire © 2011 Medscape, LLC