The bombshell report by the European Society of Human Reproduction and Embryology warned of the threat of our species being wiped out two years ago.
Since then there has been a scramble to find the answer to the disturbing question of why sperm count had dropped by an average of 1.4% per year from 1973 — 2011.
And the problem is most seriously affecting men from Europe, North America, Australia and New Zealand — with no such downward spiral seen in other parts of the world.
The study, published by Oxford University Press, said the decline in sperm count was “driven by a 50-60% decline among men” from the areas above.
“Because of the significant public health implications of these results, research on the causes of this continuing decline is urgently needed”
“Because of the significant public health implications of these results, research on the causes of this continuing decline is urgently needed,” it warned.
The analysis found that in 1973, semen contained on average 99 million sperm per millilitre.
Fast-forward to 2011 and the number was just 47 million per millilitre — a dramatic dip but still in the normal range.
Doctors don’t consider sperm count to be low until it drops below 15 million per millilitre.
But if the remarkably linear trend doesn’t taper off — as the study warns it might — the average western man could be sub-fertile by the 2060s.
Factors widely-accepted as linked to low sperm count include smoking, taking drugs, including steroids, and obesity.
But scientists studying the phenomenon insist other issues must be at play — pointing to plastic exposure and diet.
A study published in Scientific Reports on March 4 stated that soy foods and processed meats had a “deletious” impact on sperm count.
It added that the mediterranean diet was associated with healthier sperm, but noted the study didn’t factor in behaviour such as exercise while carrying out the research.
Other scientists have pointed to certain plastics as being the culprits.
The idea is that certain plastics mimic the shape of human hormones and contaminate our food and water sources.
These “endocrine disrupters” could interfere with how our bodies work — almost literally throwing a spanner in the works.
But exposure to such chemicals is actually believed to be higher in developing countries such as India — where declining sperm counts were not observed.
Commenting on the research, andrologist Allan Pacey at the University of Sheffield said historical data could’t be trusted.
“It is very hard to look back into the archives with any sense of confidence about the precision and reliability of measurements made in the past,” he wrote in a 2013 journal.