Reacción a "Geographical differences in semen quality in Spain are not linked to men’s lifestyle habits"

This study aims at assessing whether there are associations between the quality of semen samples in men attending fertility clinics and some lifestyle or individual factors in Spain. Alterations in semen characteristics have previously been reported in Spain, however the reason for these differences was not clarified. More broadly, the state of male fertility is becoming a focus of research given the reported global decrease in sperm concentration over recent decades, the overall lower fecundity, and increase in couples needing assisted reproduction to conceive. It is a field where lifestyle and exposure factors, as well as genetic determinants, intersect in creating the observed outcome. To make matters more complicated, the characteristics of semen in an ejaculate fluctuate in response to both known factors (such as abstinence) and unknown ones, so it is often necessary to analyse more than one sample from the same person to have a strong assessment.

Taking into consideration the intrinsic limitations of these types of studies, the study by Rocio Nuñez-Calonge is nonetheless interesting, particularly because it seems to conclude that there are regional differences in sperm quality that supersede the effect of self-reported lifestyle factors. If confirmed, this would indicate that the most likely exposure factors are independent from lifestyle choices such as smoking or exercising. The number of men tested in this study is quite large and this gives strength to the outcomes, however the broad division of the Spanish territory makes it almost impossible to understand what the reason of the observed differences could be. For instance, it has been shown that men living in either highly industrialized areas or in areas of intensive agriculture tend to have worse semen parameters, likely due to exposure to environmental contaminants. In the present study, we do not know the environment where the men lived, just the broad geographical region. Another point is the fact that the participants were attending a fertility clinic, and although they were receiving a semen assessment – not a fertility treatment - most men in the general population do not have these type of assessment, so that there may be an effect of self-selection of a population already at risk of altered semen parameters.

All in all, it is an interesting study in a large number of cases that opens the door to further understanding of the factors affecting male semen quality beyond lifestyle choices.