The aim of this study is to assess whether there are any associations between the quality of semen samples from men attending fertility clinics and certain lifestyle or individual factors in Spain. Abnormalities in semen characteristics have previously been reported in Spain; however, the cause of these differences has not been clarified. More generally, male fertility is becoming a key area of research, given the global decline in sperm concentration observed over recent decades, lower overall fertility rates and the increase in the number of couples requiring assisted reproductive technologies to conceive. This is a field in which lifestyle and exposure factors, as well as genetic determinants, intersect to produce the observed outcome. To complicate matters further, the characteristics of semen in a single ejaculation fluctuate in response to both known factors (such as abstinence) and unknown ones, meaning that it is often necessary to analyse more than one sample from the same individual to obtain a reliable assessment.

Given the inherent limitations of this type of study, Rocío Núñez-Calonge’s work is nonetheless interesting, particularly as it appears to conclude that there are regional differences in sperm quality that outweigh the effect of lifestyle factors reported by the participants themselves. If confirmed, this would suggest that the most likely exposure factors are independent of lifestyle choices, such as smoking or exercising. The number of men analysed in this study is quite high, which reinforces the robustness of the results; however, the vast geographical expanse of Spain makes it almost impossible to understand what might be causing the observed differences. For example, it has been shown that men living in highly industrialised areas or in areas of intensive agriculture tend to have poorer semen parameters, probably due to exposure to environmental pollutants. In the present study, the specific environment in which the men lived is unknown; only the general geographical region is known. Another aspect to bear in mind is the fact that the participants were attending a fertility clinic and, although they underwent a semen analysis—not fertility treatment—most men in the general population do not undergo this type of testing; consequently, there may be a self-selection bias in a population that is already at risk of impaired semen parameters.

In short, this is an interesting study with a large number of cases that paves the way for a better understanding of the factors affecting male semen quality beyond lifestyle choices.