A 16-year study of US sperm donors shows that sperm quality has been steadily declining, possibly due to increased chemical exposure and lifestyle changes.
at Reproductive Medicine Associates of New York, a fertility clinic, and her colleagues looked at more than 170,000 semen analyses conducted between 2005 and 2021 for healthy 19 to 38-year-olds from nine geographic regions across the US. The researchers say the data comes from a 鈥渄iverse set鈥� of men, although it is unclear how representative it is of the US population.
Across all regions, the researchers found that the average concentration of sperm in donated semen . The average number of mobile sperm in the semen 鈥� which is a better predictor of their potential to fertilise eggs 鈥� also declined.
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The results, which were presented at the annual meeting of the in Baltimore, Maryland, on 20 October, are consistent with studies showing that .
Increased exposure to air pollution and chemicals known as endocrine disruptors could be driving this trend, as well as lifestyle factors such as obesity, smoking, lack of exercise and stress, says at the University of Virginia.
Endocrine disruptors are chemicals that can mimic our hormones and interfere with their normal function. They are found in pesticides, food packaging, cosmetics and other everyday products, with growing evidence suggesting they can .
At this stage, it is unclear if declining sperm quality is making it harder to have children, says Smith. Birth rates are slipping in many countries and more people require IVF to get pregnant, but there could be many other factors explaining this, like people trying to conceive at older ages when fertility naturally wanes, he says.
鈥淎ll we can say is that we鈥檙e seeing declining sperm count 鈥� how that pertains to the bigger picture of fertility really needs further clarification.鈥�
Nevertheless, Smith believes that the use of endocrine disruptors should be more tightly regulated by governments to minimise their possible effects on sperm health.
There are also ways that individuals can improve their sperm health, for example by eating better, exercising more and quitting smoking, says Smith. 鈥淭he life cycle of sperm is about 70 days, so you can turn things around within a few months,鈥� he says.
