By conducting a meta-analysis of 185 studies published between 1973 and 2011, researchers from the Hebrew University-Hadassah Braun School of Public Health and Community Medicine and the Icahn School of Medicine at Mount Sinai documented a 52.4 percent decline in sperm concentration, and a 59.3 percent decline in total sperm count among men living in North America, Europe, Australia, and New Zealand. The same declines were not observed among men living in South America, Asia, and Africa, where fewer studies have been performed. That is a disturbing number given that, according to World Health Organization criteria, men with a sperm concentration of less than 40 million are considered to have an impaired chance of conceiving and those with a sperm concentration of less than 15 million per milliliter are unlikely to be able to have children. The men used in these studies weren’t chosen because of any suspected fertility issues. Reduced sperm is thought to be the result of environmental influences, including exposure to noxious chemicals while in the womb, exposure to pesticides, and lifestyle factors such as smoking, obesity, and stress. This definitive study shows, for the first time, that this decline is strong and continuing,” said Swan. Scientists don’t actually know what’s causing the sperm count crisis, but this study suggests the Western lifestyle may have something to do with it. “Investments should also be made into studying male reproduction.” 
 
 And indeed, the impact of low sperm counts on male fertility should be of great concern. The researchers say the reported declines in sperm production have manifested in the general population, and that “more couples are infertile,” adding that “From statistical point of view, such a large decline must implicate [a] larger proportion of infertile and subfertile men.” 
 
 
 
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 We’re nowhere near a fertility crisis at the moment, so fears of us entering into a Handmaid’s Tale world are largely overstated. “Having a low sperm count is a signal,” Swan said, “that there’s something wrong in men’s health overall.” 
 
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 The U.S. fertility rate just hit a historic low. However, Shanna H. Swan, one of the authors of the new study published in the Human Reproduction Update, said that the new meta-analysis is so broad and comprehensive, involving all the relevant research published in English, that she hoped it would put some of the uncertainty to rest.
– The Western man's sperm count just isn't what it used to be. In what the Washington Post calls the largest and most comprehensive look into the matter, an international team of researchers reports in the journal Human Reproductive Update that after analyzing 185 previous studies involving 42,000 men worldwide between 1973 and 2011, they've observed a 52% drop in sperm concentration in men from North America, Europe, Australia, and New Zealand. This is in stark contrast to men in South America, Asia, and Africa, where no such decline was found, though not nearly as much data comes out of those regions, researchers report in press release. "Given the importance of sperm counts for male fertility and human health, this study is an urgent wake-up call," the lead author says. In 1973, the researchers estimate, men had an average sperm concentration of 99 million per milliliter. The World Health Organization puts the threshold for impaired chances of conception at 40 million, and today, the average Western male's sperm concentration has dropped very close to that: 47 million. And while there isn't exactly a fertility crisis among humans, Gizmodo calls the research "admittedly scary." Having a low sperm count has been linked to a range of increased health problems and even higher mortality. It's "a signal that there's something wrong in men's health overall," one researcher tells the Post, noting that "the decline is strong and ... the decline is continuing." What's causing the drop is up for debate, and everything from chemical and pesticide exposure to smoking and stress have been blamed. (Tight underwear could be part of the problem.)