According to a new analysis published Tuesday, sperm counts in Western men have plummeted nearly 60 percent over the last four decades.
Though researchers say the specific drivers behind the trend will require further scientific investigation, current data suggest a link between the sharp decline and living in the industrialized world.
“The results are quite shocking,” Hagai Levine, an epidemiologist from the Hebrew University of Jerusalem, told The Guardian.
Levine led the international team of researchers, who examined 185 individual studies conducted between 1973 and 2011.
The analysis, published in the medical journal Human Reproduction Update, additionally revealed that on average, Western men’s sperm concentration — the number of sperm within a semen ejaculate — is falling 1.4 percent a year.
Added up, that calculates to an overall drop of more than 50 percent since the early 1970s.
“This is a classic under the radar huge public health problem that is really neglected,” said Levine. The team notes in its report that recent studies have shown an association between poor sperm counts and overall morbidity and mortality.
Unlike with Western nations, the team found no similar trend among the male populations of less-developed countries, such as those in Africa and South America.
“Therefore,” the team writes, “sperm count may sensitively reflect the impacts of the modern environment on male health throughout the life course.”
Researchers acknowledge, however, that far fewer studies have been conducted in those nations and that more data needs to be compiled before a final conclusion can be drawn.
While the scientific community seems to agree that the Western trend is likely being driven by a confluence of factors, one member of the team, Professor Shanna Swan of the Ichan School of Medicine in New York, told the Independent that the lack of declining sperm counts in less-industrialized nations is something that can’t be ignored.
“The fact that the decline is seen in Western countries strongly suggests that chemicals in commerce are playing a causal role in this trend,” she said.
Just as startling as the trend, says Professor Richard Sharpe of Edinburgh University, is the fact that it shows no sign of slowing down. Speaking to The Independent, Sharpe, who was not involved with the research, said:
“As the authors point out, the continuous nature of the decline is of as much concern as the decline itself, given that we still do not know what lifestyle, dietary or chemical exposures might have caused this decrease.”
Calling the trend “real beyond any reasonable doubt,” Sharpe says that with more and more women wanting to have babies later in life when conception is considerably more difficult, there now exists a “double whammy for couple fertility” in Western societies.
“Therefore, looking ahead,” he said, “I can only conclude that couple infertility is set to increase. Hopefully, this new study will serve as a wake-up call for health and research authorities as well as for the public, and for young people in particular.”