Sperm counts have been declining for years, and new research shows the problem is getting worse
Two key measures related to male fertility – sperm count and concentration – have fallen sharply in recent years, according to a new study, fueling fears about future population growth.
From 1973 to 2018, sperm concentrations worldwide fell by more than half, according to a new analysis by an international team of researchers, published in Update on human reproduction diary on Tuesday. Meanwhile, the total sperm count fell by 62.3% over the same period.
“Overall, we are seeing a significant global decline in sperm counts of over 50% over the past 46 years, a decline that has accelerated in recent years,” said the lead researcher and professor at the Hebrew University of Hadassah Braun School of Public Jerusalem Health, Hagai Levine said in a statement.
A 2017 publication by the same researchers found that sperm count declines were accelerating in North America, Europe, Australia and New Zealand, based on samples collected between 1973 and 2011.
The more recent study, which builds on earlier findings, looked across South America, Asia and Africa to understand the decline in sperm counts around the world. Using samples from over 57,000 men from 53 countries, combined with statistics used in previous studies, the researchers found that men in these regions also experienced significant drops in sperm count as in the previous study.
Researchers found that sperm concentration has dropped by 1.16% every year since 1972. However, when researchers looked at data from after 2000, they found that the annual decline was 2.64%.
“Our findings serve as a canary in a coal mine,” Levine said. “We are dealing with a serious problem that, if not mitigated, could threaten the very survival of humanity. We call for urgent global action to promote a healthier environment for all species and to reduce exposures and behaviors that threaten our reproductive health.”
The analysis doesn’t examine the causes of the decline in sperm concentration and count, but Levine said that “lifestyle habits and chemicals in the environment affect this fetal development.”
The study comes on the same day the world population hit 8 billion, according to the UN estimate. But all signs point to an overall slowdown in population growth. It took the world population 12 years to grow from 7 billion to 8 billion, but it is expected to take another 15 years to reach 9 billion.
Meanwhile, the UN says fertility has fallen in several countries in recent decades. And the “cumulative effect of lower fertility, if sustained over several decades, could lead to a more pronounced slowdown in global population growth in the second half of the century,” the director of the UN’s population division said in a statement.
In the analysis, the researchers note that sperm count is an “imperfect predictor of fertility,” but sperm concentration and count are closely linked to chances of fertility.
“At the population level, the decline in the mean [sperm concentration] from 104 to 49 million/mL, which we report here, indicates a significant increase in the proportion of men with delayed conception,” the researchers wrote in the study. “Hence, [sperm concentration] provides the most stable and reliable measure for comparisons within and between populations and over time.”
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