Why Fathers Are Less Likely to Die of Heart Disease

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Having children may drain a man’s testosterone, but a large family may also be an indicator of heart health, a new study finds.

Researchers led by Dr. Michael Eisenberg at Stanford University School of Medicine report in the journal Human Reproduction that men who didn’t have children were 17% more likely to die over a period of 10 years than men who were fathers. The more children a man had, the less likely he was to die of heart-related problems, the authors found.

Given that childlessness is a good marker for fertility problems, Eisenberg, a urologist who specializes in male infertility, was interested in using it to better understand how a man’s fertility might affect his health over the long term. Previous studies have shown that men who have difficulty conceiving have higher rates of cancer, particularly of the testes, and that they also tend to die sooner than similarly matched fertile men.

Eisenberg hoped his study would shed light on how infertility, which surfaces early in the course of a man’s lifetime, may serve as a warning of possible health problems down the road.

To do that, he and his colleagues consulted data from the National Institutes of Health­–American Association of Retired Persons Diet and Health Study, in which more than 137,000 healthy men were followed for 10 years. The researchers tracked the number of children the men reported having. To increase the likelihood that all the men included in the study actually wanted children, the researchers excluded those who had never been married; by including only men who were married or had been married at least once, the researchers could be reasonably sure they had the desire and opportunity to have kids. The study also focused on men who were relatively healthy and didn’t have a history of heart disease.

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The team then followed the participants for a decade, and tallied the number of deaths from about 70 different causes. Overall, the researchers found, childless men were more likely to die during the follow-up period than fathers, and most of the deaths were heart-related.

“All of the trends were a little surprising and concerning,” says Eisenberg. “We knew that infertile men are at higher risk of malignancies, especially in the testes. So we were expecting cancer deaths to be higher, but we were surprised that they weren’t.”

On the other hand, because infertile men tend to have abnormal testicular function, and the testes are responsible for making testosterone, it does make some sense that childlessness might be connected to heart disease. “There is solid evidence at this point that having low testosterone can increase the risk of all cause morality and heart disease deaths,” says Eisenberg (abnormal testosterone levels may cause HDL, or “good” cholesterol, to drop), “So perhaps this impaired testicular function, which is [showing up] as infertility early in life, sets the stage for a higher risk of cardiovascular events later in life.”

Of course, Eisenberg isn’t saying that having fewer children necessarily means that men are destined for heart disease. There are plenty of factors other than infertility that figure prominently in family size, such as cultural norms and financial pressure.

The study also did not track men’s cholesterol or blood pressure measurements, which are important risk factors for heart disease. And it did not gather information on the fertility of the men’s partners, which also could have affected family size.

Further, it’s possible that having kids — like being married or having a pet or a lot of friends — may have lowered men’s heart risk by boosting their health overall.

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Still, the study was large and its results may point to a potentially useful way to identify men who could have a higher risk of heart-related events later in life. Fertility problems and heart risk may share some underlying biological processes, which is why Eisenberg says he may counsel men who come to see him for infertility about their risk of heart disease as well. The good news, he says, is that “things that are good for the heart are good for reproduction as well — exercise, eating a healthy diet, and maintaining a normal body weight.”

Alice Park is a writer at TIME. Find her on Twitter at @aliceparkny. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.