Better semen quality linked to men living longer

Men’s semen quality is associated with how long they live, according to a study of nearly 80,000 men which has been published in the journal Human Reproduction. This is understood to be the largest study to examine the link between semen quality and mortality, and has been described in an accompanying editorial as a “landmark” publication.

The research was led by Dr Lærke Priskorn and Dr Niels Jørgensen, both from Copenhagen University Hospital — Rigshospitalet. They analysed data from 78,284 men who had their semen quality assessed between 1965 and 2015 at the public semen analysis laboratory in Copenhagen due to reported couple infertility. This meant that semen quality among the men ranged from very good to those with no sperm. Assessment of semen quality included semen volume, sperm concentration, and the proportion of sperm that were motile and a normal shape.

During the follow-up period, the researchers used the data contained in Danish national registers to see how many died from any cause. During this time there were 8600 deaths, representing 11% of this group of men. Out of this group, 59,657 men provided semen samples between 1987 and 2015, and for this group more information was available, including educational level as an indicator of socioeconomic status, and registered diagnoses of medical conditions in the 10 years prior to giving a sample. The researchers adjusted their analyses to take account of the extra information that was available for the men who gave samples from 1987 onwards, as that could affect the results.

“Previous research has suggested that male infertility and lower semen quality could be associated with mortality,” Priskorn said. “We conducted this study to test the hypothesis and at the same time get an absolute estimate of how much semen quality predicts a man’s lifespan and to understand whether diagnosed diseases prior to semen quality assessment might explain some of the reported association.

“We calculated the men’s life expectancy according to their semen quality and found that men with the best quality could expect to live two to three years longer, on average, than men with the lowest semen quality. In absolute terms, men with a total motile count of more than 120 million lived 2.7 years longer than men with a total motile count of between 0 and 5 million. The lower the semen quality, the lower the life expectancy. This association was not explained by any diseases in the 10 years before semen quality assessment or the men’s educational level.”

The researchers suggest that poor semen quality may be an indicator of other, underlying factors that affect both fertility and overall health. This might have the potential for detecting health problems at the time men have their semen quality investigated.

“We need to better understand the association between semen quality and men’s general health,” Jørgensen said. “However, this study suggests that we can identify subgroups of men with impaired semen quality who are apparently healthy when their semen quality is assessed, but who are at increased risk of developing certain diseases later in life.

“Thus, fertility evaluations, which are typically conducted when the men are relatively young, would serve as an opportunity for detecting and mitigating the risks of other health problems in the longer term. In the current study, we did not analyse whether poor semen quality was associated with earlier deaths from particular causes, such as cancer or heart disease, and this is something we will be studying in the future. Using other groups of men, we will also try to identify relevant biomarkers that can identify subgroups of men at increased risk. This is key to initiating relevant prevention strategies.”

While a strength of the study is its large size, limitations include lack of information on health behaviours; assessment of the men’s health before semen sampling was limited to diagnoses obtained from the National Patient Register, and only for men who gave samples from 1987. It was also not possible to distinguish between men who had no motile sperm because of an obstruction in their genital tracts and those who had no motile sperm for other reasons.

In his accompanying editorial, Distinguished Emeritus Professor John Aitken from The University of Newcastle set out the various mechanisms that could be contributing to the link between poor semen quality and shorter lifespan.

“There are a range of factors to consider — genetic defects on the sex chromosomes (X or Y), a compromised immune system, comorbidities, lifestyle factors and chemical pollutants capable of compromising telomeric integrity in DNA,” he said.

Aitken suggests a process called oxidative stress could be involved in the process. This is an imbalance in the body of molecules called ‘free radicals’ and antioxidants, which inhibit oxidation. Free radicals are known to damage cells and to influence semen quality, and oxidative stress is known to be involved in the aging process.

“I think oxidative stress could well be a single mechanism that connects the sperm count in the male with his lifespan,” Aitken said.

“Women tend to have higher levels of antioxidant in their bloodstream than men. Consequently, women have longer telomeres — the little bits of chromosome that define your lifespan.

“We know that the average lifespan of women is more than their male counterparts.”

Further research is needed to confirm this hypothesis, but Aitken said if oxidative stress is to blame for reduced lifespans in men, then there is hope we can prevent it.

“Health professionals can monitor levels of oxidative stress and determine if a patient needs to take antioxidant supplements,” he said.

Image credit: iStock.com/Shidlovski