Men’s sperm have been decreasing in number and getting worse at swimming for some time now—and, at least in the United States and Europe, new research says it’s getting worse. A pair of new studies unveiled this week at the Scientific Congress of the American Society for Reproductive Medicine (ASRM) in Denver suggest that American and European men’s sperm count and sperm motility—that is, the “swimming” ability of sperm cells—have declined in the past decade, which follows a similar, broader trend observed by many scientists over the past few decades.
One study presented at the ASRM summit, conducted jointly by a fertility center in New Jersey and a fertility center in Spain, found that the percentage of nearly 120,000 male infertility patients whose total motile sperm count (TMSC) numbered more than 15 million (sperm counts below which are considered low, according to the Mayo Clinic) decreased from 85 percent in the 2002–05 period to 79 percent in the period of 2014–17. The percentage of patients whose TMSC clocked in between zero and 5 million, meanwhile, increased from 9 percent to more than 11.5 percent.
The other study, conducted by researchers at Mount Sinai’s Icahn School of Medicine in collaboration with the California Cryobank and Reproductive Medicine Associates of New York, compared more than 124,000 samples from 2,600 sperm donors between the ages of 19 and 38 in Los Angeles, Palo Alto, Houston, Boston, Indianapolis, and New York City. The researchers found that total sperm count, sperm concentration, and TMSC all decreased over time from 2007 to 2017—except in New York City, where all three parameters held steady. (In Boston, too, the researchers note, sperm count held steady, while concentration and TMSC declined.) “Given that donors have higher than average sperm counts, these trends would likely be magnified in the general population,” writes the lead study author, Sydney Chang, a fellow at Reproductive Medicine Associates of New York.