A New Study Finds That Men With Better Sperm Live Longer

This commentary is a repost from “Sex on Wednesdays” by Martha Kempner on Substack. Find her other articles on The Queen Zone here.

A new study out of Denmark finds that men with better sperm quality at young ages seem to live longer than those who have weak swimmers. Before you ask the men in your life to provide semen samples for predictive purposes, however, you should know that researchers still don’t understand why this association exists or what it means. (Other than, you know, the obvious: healthy men make healthy sperm and healthy men tend to live longer connection.)

A Large-Scale Study on Sperm Motility and Longevity

The study is based on 78,284 men who had their semen tested at the public semen analysis lab in Copenhagen between 1965 and 2015. (Yes, Copenhagen has a public semen analysis lab.) The men ejaculated into a cup not for science, but because they and their female partner were experiencing infertility. This means that there was a wide variety in the semen samples. Some men may have been shooting blanks, but others had perfectly healthy sperm that were being thwarted by any number of female infertility issues. In addition to having a public semen analysis lab (are their field trips available), Denmark has a national health register. This allowed researcher to follow the health of these same men for decades.

The Link Between Sperm Quality and Mortality Risk

Men who are experiencing infertility are often tested for three things: sperm count, sperm shape, and sperm motility. This study was most interested in motility which is the ability of sperm to swim efficiently. Remember, sperm are very little and have to go a long way to get through the cervical mucus (Hi, Cecily!), cervix, uterus, and fallopian tubes where they may or may not find an egg. Motility tests look at how fast the little guys swim (at least 25 micrometers a second is required to get to the egg goal) and whether they’re going full speed ahead or full speed around and around in useless circles. The more goal-oriented speedsters, the better: >120 million motile sperm per milliliter of ejaculate (referred to as total motile sperm count or TMSC) is considered healthy.

This study found that men with a TMSC of 120 million or more had a life expectancy of 80.3 years compared to 77.6 for men who had 0 to 5 million sperm per milliliter. As motile sperm count went down, mortality risk went up. Men with a TMSC of 80 to 120 million had a 16% higher mortality risk, 40 to 80 million a 27% higher mortality risk, and 10 to 40 million had a 38% higher mortality risk.

Some men in the study had azoospermia meaning their semen samples had very few or no motile sperm. Men with a TMSC of 0 to 5 million had a 39% higher mortality rate than those with the swimmiest sperm. Interestingly, though, the highest mortality risk (61%) was for men with a TMSC of 5 to 10 million. The researchers believe this is because their study didn’t distinguish between azoospermia caused by sperm quality and that caused by an obstruction. Men with the lowest TMSC may be producing healthy sperm but not able to release them. This would be problem for getting someone pregnant, but possibly not an indication of poorer overall health. In contrast, men with some, but not many, swimmy sperm are likely not hiding healthier ones back in the ball sack.

What Does This Mean for Men’s Health?

The association between lower semen quality and lower life expectancy remained after researchers controlled for education levels. It was also not explained by diseases in the 10 years before the semen was tested. However, in each category of sperm health, men with pre-existing conditions fared a little worse than their peers.

Sperm quality as a marker of overall health is an interesting finding and one that countless startups will undoubtedly try to capitalize on. (I see an ad campaign built around a fortune teller looking into a microscope instead of a crystal ball.) The problem is that we don’t yet know what it’s telling us. The correlation is clear, but the connection is just as murky as those public semen samples.