Semen quality linked to longevity in men

Men's semen quality is associated with how long they live according to a study of nearly 80,000 men, which is published today (Wednesday) in Human Reproduction, one of the world's leading reproductive medicine journals.

The study followed the men for up to 50 years and found that those with a total number of motile sperm (sperm that can move or 'swim') of more than 120 million could expect to live two to three years longer than men with a total motile sperm count of between 0 and 5 million.

This is the largest study to examine the link between semen quality and mortality. An accompanying editorial commentary calls it a "landmark" publication.

The research was led by Dr. Lærke Priskorn, a senior researcher, and Dr Niels Jørgensen, chief andrologist, both working in the Department of Growth and Reproduction at Copenhagen University Hospital-Rigshospitalet, Copenhagen, Denmark. 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 unique Danish national registers, to see how many died from any cause. During this time there were 8,600 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 ten 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.

Dr. Priskorn said: "Previous research has suggested that male infertility and lower semen quality could be associated with mortality. 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 ten 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.

Dr. Jørgensen said: "We need to better understand the association between semen quality and men's general health. 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."

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; and it was 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 a commentary to accompany the paper, Distinguished Emeritus Professor John Aitken from the School of Environmental and Life Sciences at The University of Newcastle, Australia, calls it a "landmark" publication and sets out the various mechanisms that could be contributing to the link between poor semen quality and shorter life span.

"In this commentary, I have highlighted several potential mediators of such an association including genetic defects on the sex chromosomes (X or Y), a compromised immune system, comorbidities, lifestyle factors and chemical pollutants capable of compromising telomeric integrity. Given the complexity of these factors, we might ask whether they are acting independently, or do they reflect the existence of some fundamental pathological process that cuts across all of these epidemiological pathways?" he writes.

He 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.

He writes: "Any factor (genetic, immunological, metabolic, environmental or lifestyle) that enhances overall levels of oxidative stress, could reasonably be expected to drive changes in the semen profile and subsequent patterns of mortality, as observed by Priskorn et al. . . . Furthermore, an aetiology grounded in oxidative stress might also explain the relationships observed between complications of pregnancy (preeclampsia, gestational hypertension and gestational diabetes) and female mortality later in life . . . An overarching oxidative stress hypothesis also accords with the observation that circulating antioxidant levels are generally higher in women than men, just as their telomeres are usually longer . . . So perhaps, for both genders, the secret to achieving both high fecundity and heathy ageing, is to monitor oxidative stress and adopt measures to maintain a balanced redox state. Could it be that simple? Clearly, much food for thought."