Sperm counts worldwide have plummeted by 62 percent since 1973, according to new Israeli-led research.
The study sounds alarm bells for both male fertility and for male health in general, its authors said. This is because low sperm count is considered an indicator of men’s health, with low levels being associated with increased risk of chronic disease, testicular cancer and a decreased lifespan.
“We should be amazed and worried by the finding,” said Prof. Hagai Levine of the Hebrew University of Jerusalem, who led the peer-reviewed study together with Prof. Shanna Swan at New York’s Icahn School of Medicine.
“The trend of decline is very clear,” told The Times of Israel. “This is a remarkable finding and I feel responsible to deliver it to the world. The decline is both very real and appears to be accelerating.”
Levine’s last study on sperm count, in 2017, garnered widespread attention after it reported that sperm counts among men from America, Europe, Australia and New Zealand dropped by more than 50% between 1973 and 2011. The new study, which covers 1973 to 2018, has seven more years of statistics, and is far wider in geographical reach, covering some 53 countries.
Levine and his colleagues reached their conclusion by crunching numbers from hundreds of peer-reviewed studies and adjusting overall statistics in an attempt to eliminate potentially distorting data. For example, men who checked their sperm count because of fertility problems were not included in the new study.
The research paper was published on Tuesday in the journal Human Reproduction Update. The 62% drop relates to sperm count, meaning the number of sperm present in an average ejaculation.
The sperm concentration per milliliter of semen is down 52% and stands at about 50 million. This is still well above the World Health Organization’s cutoff below which men are considered to have a low sperm concentration, namely 15 million per milliliter.
But Levine pointed to research that suggests fertility starts to dip when sperm concentration goes under 40 million per milliliter — and said that at the rate of current decline, that number is set to be the global average within a decade.
“What is more, we’re looking at averages, and if men are today averaging 50 million sperm per milliliter, there are large numbers of men who today have under 40 million sperm per milliliter — in other words, fertility that is actually suboptimal.”
Discussing the overall findings of the study, Levine said: “Our findings serve as a canary in a coal mine. We have a serious problem on our hands that, if not mitigated, could threaten humankind’s survival. We urgently call for global action to promote healthier environments for all species and reduce exposures and behaviors that threaten our reproductive health.”
He said that his study doesn’t explore what is causing the decline in sperm count and concentration, but other researchers have linked falling sperm counts to widespread obesity, sedentary lifestyles, smoking, exposure to certain chemicals and pesticides, and other factors.
Swan said that plummeting sperm counts are part of a wider decline in aspects of mens’ health.
“The troubling declines in men’s sperm concentration and total sperm counts at over 1% each year as reported in our paper are consistent with adverse trends in other men’s health outcomes,” she said. “These include testicular cancer, hormonal disruption and genital birth defects, as well as declines in female reproductive health. This clearly cannot continue unchecked.”