Men with better quality sperm can live up to three years longer than their peers with slower swimmers, a study has found.

Researchers analysed data on semen quality from nearly 80,000 men who were followed for up to 50 years.

They found that men with more than 120 million motile sperm – sperm that can move or 'swim' – could expect to live two to three years longer than those with less than 5 million motile sperm.

The 'landmark' study is the largest to examine the link between semen quality and mortality.

The research was led by Dr Lærke Priskorn, a senior researcher, and Dr Niels Jørgensen, chief andrologist, who both work in the Department of Growth and Reproduction at Copenhagen University Hospital.

They looked at data from 78,284 men who had their semen quality assessed as part of a couple's infertility examination.

This meant that semen quality among the men ranged from very good to those with no sperm at all.

Assessment of semen quality included semen volume, sperm concentration and the proportion of sperm that were motile and a normal shape.

'Previous research has suggested that male infertility and lower semen quality could be associated with mortality, Dr 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 link was not explained by any diseases in the 10 years before semen quality was assessed or the men's education level, she explained.

The team suggest that poor semen quality could indicate there are other underlying factors that affect both fertility and overall health.

As a result, there could be potential for detecting health problems at the same 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.

'Therefore 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.'

Future research could include analysing whether poor semen quality is linked with earlier deaths from particular causes such as cancer or heart disease, the team said.

In an accompanying commentary, Professor John Aitken from the School of Environmental and Life Sciences at the University of Newcastle, Australia, described the study as a 'landmark' publication.

He said a process called oxidative stress could explain the link.

This occurs when the body has too many molecules called free radicals and not enough antioxidants.

Free radicals are known to damage cells and to influence semen quality, while oxidative stress is known to be involved in the ageing process.

The findings were published in the journal Human Reproduction.

HOW DO SPERM MOVE?

Sperm are vital in human reproduction and the motility of the male cells is crucial. 

In order to help the sperm cells move, they evolved a 'tail' which is called  a flagellum.

Sperms' tails play a critical role in their ability to swim and consequently fertilise an egg.

Sperm tails consist of around 1,000 building blocks, including structures known as tubulins, which form long tubes.

Attached to these tubes are moving molecules called motorproteins.

These pull and bend sperm tails, enabling them to swim. 

The movement of the tail is powered by a mitochondria, the powerhouse of a cell, which produces energy.