The quality of human sperm has been declining in the past 80 years. Men’s sperm count is getting lower, and the sperm themselves are becoming worse swimmers, and research says that at least in the U.S. and Europe, it is only getting worse, according to The Atlantic.
Two studies unveiled at the Scientific Congress of the American Society for Reproductive Medicine (ASRM) find that sperm count and sperm motility for American and European men has declined in the past decade, which follows a similar trend observed by scientists over the past few decades.
One of the two studies found that the percentage of almost 120,000 male infertility patients who have a total motile sperm count (TMSC) over 15 million (TMSC below that are considered low) decreased from 85% from 2002-2005 to 79% from 2014-2017. The percentage of patients whose TMSC was between zero and five million increased from 9% to over 11.5%.
The second study compared over 124,000 samples from 2,600 donors from age 19 to 38. The donors total sperm count, concentration, and TMSC all decreased gradually from 2007-2017. “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.
Men who are already experience infertility are decreasing further decreases in viable sperm, and men who are fertile are also experiencing firm decreases.
Researchers have not found a definitive cause for the trend. In the late 1980s, researchers suggested environmental pollution was the cause of the decreased sperm production. They also speculated that lifestyle factors such as stress, smoking, and drinking, could be factors in the decline. Clinical Chemistry hypothesized a few years later, in 1995, that perhaps “exposure to environmental estrogenic agents during fetal and childhood development” was a factor. Some scientists now believe that the unprecedented amount of chemicals which routinely enter the human body are a primary cause.
A 2017 study from the Hebrew University and Mount Sinai medical school found that sperm counts had declined over 50% from 1973 to 2011 among nearly 43,000 men in North America, Europe, New Zealand, and Australia. The next phase of these studies will be to figure out exactly why and how this phenomenon is occurring.
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