A new study published in the journal Human Reproduction suggests that men who are infertile as a result of defects in their semen are more likely to have a shorter lifespan, compared with men without such abnormalities.
Infertility affects approximately 7.3 million couples in the US. According to the American Society for Reproductive Medicine, the male partner is either the sole cause or contributing cause of infertility in around 40% of cases.
A number of factors may contribute to male infertility, but one of the most common causes is abnormal sperm production or function. These abnormalities can be triggered by various health problems, such as genetic defects, diabetes, undescended testicles and enlarged veins in the testes.
According to the research team, led by Dr. Michael Eisenberg of Stanford University School of Medicine in California, this latest study is the first in the US - and only the third worldwide - to look at how infertility affects mortality.
Two or more semen abnormalities 'more than doubled risk of death'
To reach their findings, the researchers analyzed the medical records of 11,935 men aged between 20 and 50 years who had visited either Stanford Hospital & Clinics between 1994 and 2011, or the Baylor College of Medicine in Texas between 1989 and 2009, for potential infertility.
The team looked at data that detailed aspects of the mens' semen quality, including motility and shape of the semen and total semen volume and sperm counts.
They were able to monitor the mens' mortality for an average of 8 years by assessing data from the National Death Index and the Social Security Death Index.
Men who had two or more sperm abnormalities at their initial fertility examination had more than double the risk of dying during the 8-year follow-up period, compared with men who had no semen defects.
Result of the analysis revealed that men who had two or more sperm abnormalities at their initial fertility examination had more than double the risk of dying during the 8-year follow-up period, compared with men who had no semen defects.
These findings remained even after the team made their best efforts to account for other influential factors at study baseline, such as age and pre-existing medical conditions.
Of the almost 12,000 men studied, 69 died during the follow-up period. The researchers admit this is a small number, but they say it reflects the patients' "relative youth," since subjects were an average age of 36.6 years.
They add that it also demonstrates that men who are assessed for infertility are more likely to have an above-average socioeconomic status, which means they are more likely to have better diets, education and access to health care.
Supporting this theory, they note that most of the men involved in this study died at a slower rate than the general male population in the US, regardless of whether or not they had semen defects.
But regardless of this hypothesis, the team says their findings indicating that men with two or more semen defects have increased mortality risk is "statistically significant."
Further investigations in progress
The team admits that infertility could have been caused by any medical conditions the men may already have. Therefore, it is "plausible" that increased mortality risk may be caused by these health problems, rather than infertility itself.
"But we controlled for this factor as best we could," says Dr. Eisenberg, "and while that did attenuate the measured risk somewhat, there seems to be something else going on."
"Could it be genetic, developmental or hormonal factors? Or could it be that something about the experience of having and raising kids - even though you may sometimes feel like they're killing you - actually lowers mortality?"
He adds that the team is in the process of further investigations in collaboration with medical centers in the US and Canada, which they hope will answer these questions.
In 2013, Medical News Today reported on another study led by Dr. Eisenberg, which found that men who have no sperm have a higher risk of developing cancer, compared with males who have a normal sperm count.