Sperm may have become as lazy as the men who produce them, boffins have found.
Academics had believed counts were dropping across the planet resulting in a birth rate slow down. But new research shows levels may not have dropped.
Instead – like many of the blokes who produce them – sperm just cannot be bothered to move. Experts blame “changes in working patterns, diet and levels of physical activity” since lockdown for sperm stopping swimming.
That means they are simply not trying as hard to fertilise eggs. Researchers analysed data from 6,758 Danish men applying to be donors at the world’s largest sperm bank Cryos International.
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The study – by the universities of Manchester and Queen’s in Kingston, Canada, published in the journal Human Reproduction – showed the average sperm concentration has not significantly changed in the past six years.
But their motility, ability to swim, has dropped. Co-author Professor Robert Montgomerie said: “The decline in measures of sperm motility between 2019 and 2022 was an unexpected finding.
(Image: GETTY)
“This decline roughly corresponds to the onset of the worldwide Covid-19 pandemic. While there is no evidence to suggest that the SARS-CoV-2 virus is directly affecting sperm, 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.’’
Experts found the number of swimming sperm provided for testing had declined by 22% from 2019 to 2022. Co-author Professor Allan Pacey said: “It is commonly believed by that sperm counts in men are falling.
“This is to some degree the result of meta-analysis published in 2023 which proposed that sperm concentrations worldwide had declined as much as 2.64% per year in unselected men since the year 2000.
“We did not see such a change and that suggests that in this population of sperm donor applicants, in these four Danish cities, sperm concentrations have not changed between 2017 and 2022.”
The study authors were not able to collect information on the health or lifestyles of the men applying to be sperm donors that could identify factors that may account for the decline in motility.
But they said monitoring the candidates could be a useful way to assess changes in human semen quality over time.
Anne-Bine Skytte, medical director of Cryos International, said: “Men who apply to be sperm donors are doing so in order to help women and couples achieve their family wishes.
“We have no way of knowing how random this sample is with respect to the general population.
“But this study shows that another altruistic outcome of applying to be a sperm donor is how the data can now be used to help answer big science questions like whether sperm counts are declining or not. This is an unexpected benefit of their generosity.”