Dr. Robert Eckel is past president of the American Heart Association and professor of medicine at the University of Colorado, Denver and he explains that in men higher levels of testosterone are considered to be healthier. However if the amount is excessive or not enough then good cholesterol (HDL) may fall and that is a major player in heart attack risk. He acknowledges that this the subject of fertility and mortality is becoming, as he puts it, “a hot topic”. But he also stresses that everyday life with its stresses from jobs and lifestyle also influences the risk of someone developing heart disease.

In this study the researchers understood that stress could not be measured but other factors affecting the survey were taken into account. The researchers looked at over 500,000 individuals aged over 50 who took part in an earlier survey on behalf of the National Cancer Institute in the 1990’s. Men who were never married were excluded due to their lack of opportunity to father children, as were men who had cancer or heart disease because only healthy individuals at the start of the study were to be compared.

The men who remained totaled 137,903 men and 92 percent were fathers. Half of them had been a father three times or more. The follow up after 10 years showed that approximately 10 percent of the men had died. The death rates were calculated in relation to the number of children each man had fathered. Factors such as whether the man was a smoker, age, weight, socio economic differences, household income and other factors were all taken into account.

The death rates between fathers and men who had never fathered a child were the same. But men who had been fathers were 17% less likely to have cardiovascular problems than men without children.

However the study has limitations. No figures are available relating to the number of fertile men who married infertile women or the number of fertile men who remained childless through choice. Today it is accepted that major risk factors relating to heart disease are blood pressure and cholesterol levels, yet no information on this area was available. And because there was less than 5% blacks and other minorities involved in the study it is not known if the finding also reflects their risks.

Even after these limitations have been identified the sheer scale of the study and the steps taken by the researcher to try to negate the effects of external factors makes it an important work according to some heart experts. Dr. Eric Topol, a cardiologist and genetics expert at Scripps Health in La Jolla, California says, "I think there's something there, whether it's with a pet, a spouse or social interaction … all those things are associated with better outcomes." He also asserts that social science maintains the suggestion that having children can decrease the risk of having a heart attack.

Dr. Daniel Rader, director of preventive cardiology at the University of Pennsylvania, said, “If I’m asked what can men do to remove the risk of dying from a heart attack. I'm not really prepared to, on the basis of this, tell them to start having a few kids".  Although he does not refute the connection between having children and heart attack risk, he says "It's biologically plausible that there's a connection, but the reduced risk attributed to having children is pretty modest".