There is no evidence to suggest sperm counts are declining – despite people believing otherwise, scientists have said.
Analysing data from the world’s largest sperm bank in Denmark, researchers found the average sperm concentration – the number of sperms per ml of semen – did not change between 2017 and 2022.
However, the team said they did see a fall in high quality “swimming” sperm numbers starting around the year 2020, when lockdowns had an impact on men’s diet and physical activity.
Professor Allan Pacey, of the University of Manchester, said that low sperm motility – where sperms are not able to swim efficiently – can be easily treated with a healthy lifestyle.
But he stressed the findings, published in the journal Human Reproduction, do not show any evidence that overall sperm counts are dropping.
Prof Pacey, who is one of the study authors, added that this widely held view comes from research published last year which suggested concentrations were falling by around 2.64% every year since 2000.
He said studies such as these “raise concerns” as they are based on data that is already published and not primary data.
Prof Pacey said: “It is commonly believed by that sperm counts in men are falling.
“But we did not see a change in sperm concentration (in our research), so we don’t support this idea.
“Hopefully, this will make some people feel relieved.”
For the study, Prof Allan Pacey and his colleagues looked at primary data from 6,758 men aged 18-45 from four Danish cities, between 2017 and 2022.
These men were sperm donors at Cryos International, where samples were analysed within an hour after they were produced.
The team found that from 2019 onwards, the concentration of motile sperms provided for testing declined by 16% while the total motile sperm count – which is the total number of sperm in the entire ejaculate – dropped by 22%.
Prof Pacey said sperm motility has not been investigated before so the results “are intriguing”.
He said this is because in most cases sperm counting is done manually whereas Cryos International used computers to do the job.
Study co-author Professor Robert Montgomerie, of Queen’s University in Canada, said while the fall in swimming sperm numbers was “an unexpected finding”, there is no evidence to suggest that the Covd-19 virus was directly affecting sperm.
He added: “We speculate whether the widespread lockdowns may have led to changes in working pattens, diet, and levels of physical activity which we already know can impact sperm motility.”
Prof Pacey said that monitoring the semen quality in this sperm donor population over time could provide more in-depth answers.
He said: “We will carry on looking – I will ask for the data in a few years’ time, and we will see whether it (sperm count) has bounced back or whether it has stayed the same.”
Commenting on the research, Chris Barratt, professor of reproductive medicine at the University of Dundee, said: “Studies to date have poorly investigated sperm motility but this study has done a good job.
“This data is important as it shows, on a large sample set with high quality methods, that we should be focused on sperm quality, rather than sperm quantity.”