Men’s sperm counts in North America, Australia and Europe have been dropping for the last 40 years, a new study finds. Even more alarmingly, sperm quality has deteriorated.
The research discovered that the sperm count of men in 2011 is less than half as many compared to 1973. These results raise questions on fertility and men’s health, USA Today reports. Studies have shown that men with lower sperm counts are more susceptible to heart disease, diabetes, certain kinds of cancer, even early death.
Tina Kold Jensen, an epidemiologist and professor at the University of Southern Denmark, said, “I was really scared when I saw this paper.” Jensen was not involved with this study, but she was part of research conducted 20 twenty years ago that concluded the same thing. However, that study assumed that sperm counts would recover and get back to normal in a few years. She said,
I was actually surprised by the findings. I didn’t think it would go on like that.
The researchers compiled data from 185 studies that involved 43,000 men. In some of the studies, the men had their sperm counted due to cases of infertility or other medical problems.
However, the trend in low sperm count looked stronger among men who did not have a medical reason to get checked, according to Shanna Swan, senior author on the study and reproductive endocrinologist and professor at the Icahn School of Medicine at Mount Sinai in New York.
Swan said she started her research 20 years ago after seeing reports that sperm count was declining, and hoping to prove them wrong. She conducted statistical analyses in attempts to disprove those studies. “I’ve done my best to make those declines go away,” she said. It soon became apparent that the decline was true.
Since 1973, sperm count fell an average of 1.6% every year, for a total decline of 59.3% until 20122. Sperm concentration, a marker of quality, also dropped significantly over the same time, especially among fertile men. The trend has been stable, neither improving nor worsening in recent years.
No one is quite sure why this is happening, though there are several factors that may affect sperm quality, Swan and other scientists said. These include smoking, more sedentary lifestyles, growing obesity rates, stressful events and even chemicals present in modern-day products.
The study was published in Human Reproduction Update.