It’s a dizzying fall. According to one meta-analysis, carried out by American and Israeli researchers, published in November 2022, the average concentration of gametes in men’s sperm has been halved in the space of 45 years! She was from 101 million spermatozoa per milliliter of semen in 1973, against 49 today. For the authors of this study, there is danger in delay. Is the study in question robust enough? And does it really show that there is urgency?
An article to be found in Inserm magazine n°56
The decline in male fertility is a major public health problem, reproductive health being crucial for the survival of the human species. But are the researchers right to worry? While some recognize a worrying situation, others are less alarmed. And if the interpretations diverge, consensus is emerging on the public policies to adopt concerning reproductive health, as reported by our panel of experts, made up of an epidemiologist and two clinicians.
Luc Multigner: “Decline or not, the important thing is to identify the risk factors for male infertility”
The debate over declining sperm quality began in the 1970s and continues today. Thus, a recent meta-analysis comes to contradict the conclusions of that of November 2022. While the underlying question is important, in connection with the survival of the species, the arguments of each other are too often opposed without nuance. Objectively, the available epidemiological data do not allow a decision to be made, given the inherent selection of the populations studied (fertile, infertile, sperm donors). The absence of prospective studies on representative samples of the general population prevents any conclusion. If the decline is real, one would expect an increase in the percentage of couples having difficulty conceiving a child. But here again, estimates of the frequency of involuntary childlessness vary according to the studies and methodologies used and contradict each other in terms of their evolution over time. Decline or not, the important thing is to identify the risk factors for male infertility. Some are known, whether genetic, medical, occupational or environmental. Preventative actions are already possible. This involves training professionals and informing people of childbearing age, especially young people. However, we still have a lot to discover. Research must pay attention to the contribution of our lifestyles, whether it is the impact of stress, physical inactivity or eating behaviors that promote obesity. The same applies to pollution of a chemical or physical nature.
Luc Multigner is an epidemiologist and research director Inserm at the Institute for Health, Environment and Occupational Research (Irset, unit 1085).
Samir Hamamah: “I plead for the creation of a “reprotoxic” logo which would be displayed on certain products”
The situation is worrying. Male reproductive health is impaired and men on five continents have lost more than 50% of their sperm production. We need advocacy to protect the human species. Let’s look at the numbers: since Carlsen’s study in 1992, the quality and quantity of sperm continue to deteriorate, testicular cancer increases and the percentage of micro-penis also. We must act. To this end, I submitted a report on the causes of infertility to the government in February 2022, preamble to a national strategy to combat infertility. For me, this fight goes first and foremost through prevention, education and information. Today, in the context of sexual health, we talk to teenagers about abortion, contraception, STIs, but not about reproductive health. But it is deteriorating. It is important to convey this message, without feeling guilty and without moralizing. We recommend in our report the establishment of a long consultation dedicated to reproductive health for each adult. An initiative that cannot be done without better training of health professionals on this issue. It is also essential to inform about the risks of certain substances, in particular endocrine disruptors. I plead for the creation of a “reprotoxic” logo which would be displayed on certain products. In addition, more resources are needed for research, as well as a dedicated structure, like INCa for cancer. Today, five ministries or state secretariats are responsible for these reproductive health issues, but there is no satisfactory coordination. A national fertility institute could remedy this situation.
Samir Hamamah is a university professor, researcher in Inserm unit 1203 Early human embryonic development and pluripotencehead of department at Montpellier University Hospital, and author of the national fertility plan.
Célia Ravel: “This standard is difficult to establish, it is not a fixed parameter like blood sugar”
We must temper the message delivered by the authors of the 2022 meta-analysis. Yes, there is a drop in sperm concentration in the general population. But, on the one hand, the thresholds they observe for 2018 are still very high and, on the other hand, there is a very high intra-individual variability. Stress, severe fatigue, a recent infection with high fever, such as Covid-19, are all factors that can temporarily lower the concentration of sperm. Moreover, in consultation, if a spermogram provides an abnormal result, we ask the person to come back three months later to carry out a confirmation test. The curve of this concentration over time is jagged. It is therefore not necessary to concentrate on figures at the moment t. In 2021, the minimum concentration defined by the World Health Organization was 16 million sperm per milliliter of semen; it was set at 20 in 1999. This illustrates that this standard is difficult to establish. It is not a fixed parameter like blood sugar. Moreover, we are talking here about male infertility, whereas it is a couple problem. It is also necessary to consider the parameters in women, to have a global vision. A concentration of 5 million spermatozoa per milliliter of semen can allow fertilization if the partner is young and fertile. Young people must be informed about the notions of the biological clock. If possible, children should be made early. Finally, there are solutions for male infertility, such as micro-injection of sperm into an oocyte. But in the laboratory, with success rates of about 30%, we do not do better than nature. Be careful not to be carried away by technological promises.
Célia Ravel is a university professor-hospital practitioner, reproductive biology department-CECOS at Rennes University Hospital, researcher at Irset.