The belief that sperm counts in men are declining worldwide might not be accurate, according to a new study by researchers from the University of Manchester, Queen’s University in Canada, and Cryos International in Denmark.
The study, published in the journal Human Reproduction, used data from 6,758 men in Denmark who applied to be sperm donors at Cryos International, the world’s largest sperm bank.
Recent influential meta-analyses have suggested that sperm counts are dropping globally, which has been widely reported in the media.
However, this new study found no significant change in sperm concentration over a six-year period.
Researchers analyzed sperm samples from men applying to be sperm donors between 2017 and 2022. They found that while average sperm concentration varied year by year, it did not show a significant decline over time.
Professor Allan Pacey from The University of Manchester explained, “It’s commonly believed that sperm counts in men are falling.
This idea largely comes from a meta-analysis by Levine et al (2023), which suggested that sperm concentrations have declined by 2.64% per year in unselected men since 2000.
But our study didn’t find such a change in this group of sperm donor applicants in Denmark.”
However, the study did find a decline in sperm motility (the ability of sperm to swim) from 2019 to 2022, with motility decreasing by 16% and the total number of motile sperm decreasing by 22%.
This period corresponds to the onset of the COVID-19 pandemic.
Professor Robert Montgomerie noted, “The decline in sperm motility from 2019 to 2022 was unexpected. While there’s no evidence that COVID-19 directly affects sperm, we speculate that lockdowns might have led to changes in work patterns, diet, and physical activity, all of which can impact sperm motility.”
The researchers couldn’t collect detailed information on the health and lifestyles of the men applying to be sperm donors, which might explain the decline in sperm motility.
However, they suggest that monitoring sperm quality in this group could be useful for studying changes in human semen quality over time.
Anne-Bine Skytte, the Medical Director of Cryos International, said, “Men who apply to be sperm donors do so to help women and couples achieve their family goals.
While we can’t say how representative this sample is of the general population, this study shows that data from sperm donor applicants can help answer important scientific questions, like whether sperm counts are declining.
This is an unexpected benefit of their generosity.”
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