2023-11-10 06:30:09
This is a question that arose as soon as we started using them a lot: can electromagnetic waves from cell phones have an impact on the quality of sperm? So we’re not going to do an experiment directly on humans by subjecting them to tons of waves…
The biases of previous epidemiological studies
To partially answer this question, we have to be cunning and carry out what we call epidemiological studies. In this type of study, we relate the frequency of a biological variable to a particular behavior. In our case, we can look at the quantity, motility or morphology of spermatozoa… and link these results and trends to the lifestyle of the participants, therefore to the use of telephones. But the conclusions that can be drawn depend on the initial parameters… and previous studies, carried out in the 2000s, suffered from bias.
Rita Rahban is Assistant Professor in the Department of Genetic Medicine and Development at the University of Geneva : “They say there is an effect on motility, sperm viability, as well as concentration. The one from 2005 did not find an effect on viability, but the one published in 2008 found an effect on motility and concentration. And the problem with these studies is that in fact, obviously, through selection bias, in the selection of the population, these are men who normally come to the fertility clinic, so they may have a quality of sperm which is worse than the general population. As you see, these were samples of between 250 and 350 people, so these remain samples which are not very large and therefore where solid conclusions are difficult to have. »
A real association in healthy young men…
These scientists wanted this time to try to observe this phenomenon not in fertility clinics, but in the general population, before and following the arrival of smartphones. So this is a study carried out between 2005 and 2018. For this, they used military service which is compulsory in Switzerland. More than 2,800 young men aged 18 to 22 have graciously donated their sperm to science and answered questionnaires on their general health, their reproductive health, whether they drink, whether they smoke, what they eat… and how many times a day they use their cell phone. Very precise questionnaires to avoid the main pitfall of epidemiological studies which are confounding factors, that is to say variables which hide others. And result: there is indeed an association.
Rita Rahban is the first author of this study : “We actually found that the probability that a man has a lower sperm concentration is greater when he uses his phone more often. So basically, men who use their phones more often are more likely to have a lower sperm concentration. But we did not see an association in terms of motility or morphology. »
…but no causal link
But the characteristics of epidemiological studies never make it possible to demonstrate a causal link. Rita Rahban : « In epidemiological studies, where you have to be very careful, we are talking regarding an association study, so it is effectively a form of correlation, how one variable changes depending on another variable. So it’s simply numbers, it can be probabilities, or it can be a quantification of how much the concentration can decrease depending on the use of mobile telephony. But we cannot absolutely, in any case, from epidemiological studies, or in any case very very rarely, we can say that the use of mobile phones causes, it is the cause behind the lower sperm concentration. »
One of the rare examples where there is a proven causal link between a disease and a behavior is cancers and tobacco, because other studies have proven this direct link. Otherwise, we must keep in mind that epidemiological studies are limited to associations.
No link with infertility either
The association is real but the conclusions stop there, the authors say so themselves. And like all studies, it has limits. In this case, it was the frequency of use that was studied, i.e. the number of times a subject uses their phone, but not the number of hours they stay on it. And we should also not conclude that the telephone leads to infertility… when we look at the figures, those who use the telephone the most have an average sperm concentration of 47 million sperm per milliliter…. which is certainly lower, but which remains twice as high as the standard defining infertility according to the World Health Organization.
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#frequency #telephone #influences #quantity #spermatozoa
