The concentration of spermatozoa, one of the factors of male fertility, has dropped markedly throughout the planet in recent decades. ” The concentration in spermsperm decreased significantly between 1973 and 2018 “, summarize the authors of this work, published Tuesday in the journal Human Reproduction Updateand produced by compiling around forty preliminary studies.
This publication is on an unprecedented scale on the subject, even if it confirms the conclusions of a previous study by the same team, led by the Israeli epidemiologist Hagai Levine. This, published in 2017, had been the subject of several criticisms, in particular because its conclusions only concerned certain countries all belonging to the Western world (Read our article below). This time, after integrating more data, the authors are able to conclude that the downward trend also concerns South America, Asia and Africa. ” Moreover, the data suggests that this global decline has been continuing at an accelerated rate since the beginning of the 21st century.e century “, they write.
A considerable compilation but to qualify
The quantity of spermatozoa is one of the factors that play on male fertility, but it is not the only one. Their mobility also plays a crucial role, which is not measured by this study. This does not therefore allow us to conclude that there is a general decline in male fertility, even if it provides elements in this direction and is in line with other studies which have rather studied the causes of this trend.
We thus suspect reasons such asobesityobesitylack of activity physicalphysicalpollution and exposure to chemicals in the environment “, recalled the endocrinologist Channa Jayasena. This expert ofImperial Collegewho did not participate in the study and spoke to the Science Media Center British, praised in this case an “important” work.
Other researchers, already skeptical of the 2017 study, qualified the conclusions of this new publication, believing that it did not resolve all the shortcomings of the previous one. ” I continue to doubt the quality of the studies, in particular the oldest ones, (…) on which this new analysis is based. “Andrologist Allan Pacey told AFP, without questioning the way the authors conducted their compilation. According to him, the evolution of the sperm count could actually reflect increasingly reliable techniques of measurement, and not the reality itself.
Recent studies have claimed that the sperm count in men is declining, especially in those from western countries, leading to doomsday stories about the possible extinction of thespeciesspecies human. But Harvard researchers have analyzed these claims by reassessing the evidence presented in a famous meta-analysismeta-analysis of 2017.
Article of Mary OrigasMary Origaspublished on May 23, 2021
In 2017, the magazine Human reproduction update had published a meta-analysis on the average concentration of sperm in men from Western countries, the most rigorous to date. According to this study, the number of spermatozoa would have decreased by 59.3% between 1973 and 2011, and this without any sign of stopping. The so-called western populations included North America, Europe, Australia and New Zealand. In contrast, in South American, Asian, and African populations, the decline in sperm count was not found to be statistically significant.
However, the study in question entered the public discourse and was put at the service of certain political narratives which affirm that the fertility of white men coming from Western countries is in imminent danger. In a new study by Harvard GenderSci Labpublished in the journal Human FertilityMarion Boulicault, Sarah Richardson and their colleagues offer an alternative hypothesis after reassessing previous claims.
Weaknesses in the declining sperm count hypothesis
Among the many criticisms, the study of the Harvard GenderSci Lab indicates that it is conceptually unjustified to make a comparison between the average sperm count of Western men in the 1970s to those of the year 2013. Indeed, this implies that the sperm count of Western men in the 1970s represents a optimum, thus insinuating that the body and the environment of Western men at this period are natural or even exemplary.
In addition, the fall in the number of spermatozoa does not make it possible to predict a fall in fertility. Indeed, the meta-analysis reports a decline from 99 million sperm per milliliter in 1970 to 47.1 million in 2013. But according to the World Health Organization (WHOWHO), the so-called “normal” range is between 15 and 259 million spermatozoa per millilitre.
Since male infertility is a complex biological and social phenomenon, it cannot be measured with the single metric of sperm count. Although theazoospermiaazoospermia – total absence of sperm in the spermsperm – guarantees infertility, researchers have found that some men with low sperm counts can conceive, while others with higher counts cannot. Take into account, for example, motility or morphologymorphology spermatozoa could have given the analysis a more qualitative dimension.
The laboratory of Harvard GenderSci Lab specializes, among other things, in the analysis of prejudices and the media’s treatment of scientific questions on sex, gender and reproduction. So he became interested in media coverage of male infertility and they noticed that some political groups were using Levine and Swan’s meta-analysis for ideological purposes, especially the speeches of theAlt-right American, white supremacist and movementmovement of men’s rights.
In their discourse analyses, Western men are represented as “vulnerable and threatened by forces beyond their control and victim of a liberal feminist environment”. Some far-right conspiracy theorists have attempted to link declining sperm counts to the erosion of social status and the feminization of Western men, going so far as to use the term be boy (man-soya) to refer to men who lack testosterone.
In addition to promoting a distorted image of what contributes to male reproductive health in contemporary societies, these claims obscure the fertility struggles experienced by men in East Asia, the Middle East or the South and the prejudices environmental factors on reproduction, such as the effects of endocrine disruptorsendocrine disruptors.
A new approach
The study conducted by the Harvard GenderSci Lab offers the following alternative: “Sperm count would vary over a wide range, much of which can be considered non-pathological and typical of the human species and that above a critical threshold having more sperm is not necessarily the indicator of better health or higher likelihood of fertility. »
The authors call this the sperm count biovariability hypothesis. According to them, this approach would make it possible to apprehend in a more critical way the factors affecting the reproductive health of all men. In conclusion, the study states that “Researchers must be careful to weigh hypotheses against alternatives and consider the language and narrative frameworks in which they present their work.”
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