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Is There a Link Between Having Children and Heart Disease?
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The most common type of heart disease is often linked to a number of genetic mutations, and now new research shows that those mutations may persist in the population — rather than getting winnowed out by evolution — because the people who have them also tend to have more kids.

Coronary artery disease is the most common type of heart disease in the United States, according to the Centers for Disease Control and Prevention (CDC). It is the leading cause of death in the United States in both men and women, according to the National Institutes of Health.

Coronary artery disease happens when the arteries that supply blood to heart muscle become hardened and narrowed due to a process known as atherosclerosis, the buildup of cholesterol and other material on the inner walls of the arteries. This means that less blood can flow through the arteries, so heart muscle cannot get the blood or oxygen it needs, which can eventually lead to a heart attack. [5 Surprising Ways to Be Heart Healthy]

Previous research identified many genetic variants linked with a higher risk for coronary artery disease. Prior work also found that coronary artery disease has afflicted humans for at least thousands of years, with atherosclerosis found in ancient Egyptian mummies. These findings raised the question as to why evolution did not weed out these costly genetic mutations over time.

To learn more about the genetics of coronary artery disease, scientists investigated genetic data from two large research databases, the 1000 Genomes database and the International HapMap3 project. They also looked at lifetime reproductive data, such as how many children people have, from the Framingham Heart Study.

"We really wanted to understand why such a disease has persisted and is so prevalent, considering the health costs it has," said study co-author Sean Byars, an evolutionary geneticist at the University of Melbourne in Australia.

The researchers found that genetic mutations linked with a higher risk of coronary artery disease were also often linked to a greater number of children among both men and women. These findings suggest that a greater risk of coronary artery disease later in life is a tradeoff for lifetime reproductive success early in adulthood, Byars told Live Science. [10 Amazing Facts About Your Heart]

When scientists examined previous research on the 40 genes most closely linked with coronary artery disease, they found "many different traits that are potentially contributing to variation in reproduction," Byars said. For instance, some of these genes have known associations with the likelihood of having twins, the ages that women enter puberty or menopause, and the processes linked to lactation, infertility and embryonic implantation.

Future research can seek to confirm these coronary artery disease findings with larger sets of data, said study co-author Michael Inouye, of the Baker Heart and Diabetes Institute in Melbourne, Australia.

In addition, "there are other late-life occurring diseases this could also be tested on," Byars said.

The scientists detailed their findings online today (June 22) in the journal PLOS Genetics.

Originally published on Live Science.