Paris. The concentration of sperm, one of the factors of male fertility, has decreased significantly throughout the planet in recent decades, according to a study published on Tuesday.
“Spermatozoa concentration decreased significantly between 1973 and 2018”, summarize the authors of this work published in the journal Human Reproduction Update and carried out by compiling some 40 previous studies.
This publication is of an unprecedented magnitude on the subject, although it confirms the conclusions of an earlier investigation by the same team, led by Israeli epidemiologist Hagai Levine.
The latter, published in 2017, had been the subject of various criticisms, in particular because its conclusions only affected some Western countries.
This time, after having incorporated more data, the authors can conclude that the downward trend also affects South America, Asia and Africa.
“Furthermore, the data suggest that this global decline has continued at an accelerating rate since the early 21st century,” they write.
The number of sperm is one of the factors that affect male fertility, but it is not the only one.
Their mobility also plays a crucial role, but this characteristic is not measured in this study. For this reason, it cannot be concluded that there is a general decrease in male fertility, although the research contributes elements in this sense and adds to other works that studied the causes of this trend.
Possible causes of this phenomenon include “obesity, lack of physical activity, pollution and exposure to chemicals in the environment,” recalled endocrinologist Channa Jayasena.
The Imperial College expert, who was not involved in the study and spoke to Britain’s Science Media Center, praised “important” work.
Other researchers, already skeptical about the 2017 study, qualified the conclusions of this new publication, considering that it did not resolve all the shortcomings attributed to the previous one.
“I remain doubtful about the quality of the studies, particularly the older ones, on which this new analysis is based,” he told the Afp andrologist Allan Pacey, without questioning the way the authors carried out their compilation.
According to him, the evolution of the sperm count could reflect increasingly reliable measurement techniques, and not reality itself.
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