Something weird is going on with human sperm production. For decades, scientists have warned that sperm counts are dropping among Western men, but no one has really been able to prove it. In what is now the largest and most comprehensive study of its kind, scientists have presented compelling evidence in support of this rather alarming assertion, showing that sperm counts have dropped more than 50 percent in just four decades.
The sperm count decline is real and it’s not showing any signs of slowing down, according to new research published in Human Reproduction Update. 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.
Both total sperm counts and sperm concentration (i.e. the total number of sperm in a given volume) are good measures of male reproductive ability. The men used in these studies weren’t chosen because of any suspected fertility issues. Alarmingly, the rate of decline does not appear to be stopping; the downward slope was “steep and significant” even when the meta-analysis was restricted to studies done after 1995.
“Given the importance of sperm counts for male fertility and human health, this study is an urgent wake-up call for researchers and health authorities around the world to investigate the causes of the sharp ongoing drop in sperm count, with the goal of prevention,” said study lead author Hagai Levine in a statement.
Low sperm counts are often an indicator of other health problems, and are often used by doctors to predict health and morbidity. 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. Not surprisingly, low sperm counts are also associated with reduced fertility.