A man who has never had any children has a greater chance of dying from cardiovascular disease than fathers, researchers from Stanford University School of Medicine, California, reported in the journal Human Reproduction. The authors say that they do not know whether infertility is associated with an increased risk of cardiovascular disease.
Michael Eisenberg, MD, assistant professor of urology at Stanford and team tracked 137,903 men who were members of the AARP (American Association of Retired Persons) for a period of ten years. They had set out to find out whether there might be link between the number of offspring a man has had with his long-term health.
They found a link between parental status and cardiovascular risk. However, they stress that their findings in no way provide proof of a cause and effect.
"This was the largest-ever study in the United States to examine the relationship between fatherhood and cardiovascular disease."
The authors said their study was closely controlled to reduce the effects of confounding variables that could undermine their capacity to generate meaningful results.
Eisenberg says he started the study while he was doing his urologic residency training at the University of California, San Francisco. The study continued through his joining Stanford. Eisenberg wanted to find out whether the long-term health outcomes of infertile males might be different from fertile men's. He decided that a rough proxy for a man's ability to reproduce could be represented by how many offspring he had.
"So we asked: Is not having children a predictor
of death from cardiovascular disease?"
Eisenberg and team gathered data from a series of questionnaires that AARP members had completed over a decade. They eventually narrowed down their list to 137,903 men who were either married or had been married. They were all aged at least 50 years when the study began. 95% of them were Caucasian. When the study began, their median age was 62.7.
They restricted the list to men who were either married or had been married because they wanted to compare males who had the intent and the opportunity to have children.
Men with previous underlying diseases, such as stroke, heart disease or some related condition were excluded. Hence, the men in their list started off in relatively good health.
They counted mortality from between sixty and seventy different causes during the study's duration. They assessed death through various methods, including the Social Security Administration, as well as other reliable sources.
They then placed all the participants into groups according to how many children they had had. They then calculated mortality rates within each group. They factored in such variables as BMI (body mass index), smoking status, alcohol consumption, median household income, level of education, self-reported physical activity levels, and health status.
Approximately 10% of the men died during the study. About 20% of those deaths were caused by cardiovascular disease.
They found that a childless man had a 17% greater chance of dying from a cardiovascular disease compared to fathers.
Whether the fathers had had boys or girls made no difference to their cardiovascular disease risk.
Mortality from all causes was slightly higher among the childless men. However, this increase was nearly completely due to cardiovascular disease. If cardiovascular disease risk was taken out, there was no statistically significant difference between the groups.
In this study, there was no way of assessing a man's reproductive intent, Eisenberg added. Eisenberg specializes in male infertility and sexual dysfunction. However, by not including unmarried men in this study, childlessness was brought a step closer to being a proxy for infertility.
The possible connections between infertility (seen via that proxy), and a higher likelihood to die from cardiovascular disease raise an important question, said Eisenberg.
"Is there a real biological cause behind both? Maybe we should look closer at the childless group."
As infertility problems generally appear before any clear, outward signs and symptoms of cardiovascular disease, a link could help identify cardiovascular risk earlier on, resulting in earlier and more effective intervention and treatment, the authors explained.
A smaller recent study involving 600 Filipino fathers demonstrated that males with the highest levels of testosterone had a greater chance of finding a mate and becoming fathers than their peers with lower initial levels. Testosterone is the major male steroid hormone. The study also found that testosterone levels dropped when men became fathers.
If initially low testosterone levels tend to result in fewer children, this could reflect a range of underlying problems that could eventually lead to a higher risk of cardiovascular disease in later years.
Perhaps other factors are at play which influence cardiovascular health, the authors added.
"Maybe having children causes men to have healthier behaviors,
so fathers will live longer."
Other studies have found that men who live with a long-term partner tend to live longer than those who live alone.
Written by Christian Nordqvist