“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?" wonders Dr. Michael Eisenberg, assistant professor of urology and Stanford's director of male reproductive medicine and surgery. He asks because he is somewhat surprised by the results of his new study, which found that men who are infertile due to two or more abnormalities in their semen were more than twice as likely to die over an eight-year period as men with normal semen.

To investigate a possible link between male infertility and mortality, Eisenberg and his colleagues examined the medical records of a group of men from two separate infertility centers. At both clinics, data were available for several aspects of a patient's semen quality, including total semen volume, sperm counts, motility, and shape. Using public records, the investigators were also able to monitor mortality among this group for an average of about eight years.

Altogether, the research team tracked 11,935 men, who were somewhere between the ages of 20 and 50 and had visited one of the two medical centers to be evaluated for infertility. Of this group, 69 men died during the eight-year follow-up period. This may appear to be a small number, however it is still surprising in part because the men were so young — the median age was 36.6 years — but also because these men had higher-than-average earnings with better diets, education, and access to health care. Add to that, any man concerned about infertility usually lives in a reasonably healthy manner as he is wanting and expecting to soon have a child.

The 69 men who died, then, are statistically significant, the researchers said. In fact, those with two or more semen abnormalities were more than twice as likely to die during the follow-up period as those without any. Most importantly, this difference in death rates remained even when the researchers corrected for age and known diseases.

"It's plausible that, even though we didn't detect it, infertility may be caused by pre-existing general health problems," Eisenberg said in a press release. The true cause of increased mortality risk, he suggested, would be not infertility in itself, but those health problems. As semen quality may provide a marker of health, Eisenberg and his colleagues are continuing to investigate the issue at several fertility centers in both the U.S. and Canada.

Source: Eisenberg ML, Shufeng L, Behr B, et al. Semen quality, infertility and mortality in the USA. Human Reproduction. 2014.