The quality of semen is one of the most determining factors to guarantee the fertility of the population. For this reason, since last year the World Health Organization (WHO) announced that sperm concentration in men was decreasing and in Spain there was a 28% drop, many scientists began to investigate the factors that could be causing this worsening. Recently, a study carried out in Spain has shown that The quality of the men from the north of Spain notably surpassedthat of the rest of the territory.
This discovery was presented at the 42nd annual meeting of the European Society of Human Reproduction and Embryology (ESHRE). Those in charge of developing the study were researchers from the UR International Group, led by its scientific director Rocío Núñez-Calonge, who discovered that the concentration of motile sperm of men in northern Spain reached 94.35 millioncompared to 50.11 million in the central region. A result similar to that obtained in an IVI study.
However, this was not the only difference between the samples analyzed. The results revealed that the reduced mobility of the subjects from northern Spain was 23.9%compared to more than 53% that occurred in subjects from the central and southern areas of the country. A notable difference in semen quality between regions that It was not the only surprising element that they got from the results.
Lifestyle and habits are not the reason that would explain this inequality
Although it may seem that the reason behind this inequality can be explained by lifestyle, consumption of alcohol, coffee or tobacco or with the body mass index, the truth is that these variables were very similar between the chosen subjects. As Núñez-Calonge explained, “the most striking thing was to verify that the best clarity parameters were consistently found in the north of Spain, while Life habits were very similar in all the regions studied“, reports “SINC”.
To carry out this study, the researchers analyzed samples from 386 men collected in seven assisted reproduction centers in Spain during the months of June 2024 and December 2025. For the selection process, the subjects had to fill out a form in which they answered personal questions such as your body mass index, medical history, physical activity, use of alcohol, tobacco, coffee or other substances, as well as your place of residence.
Therefore, researchers had to come up with another theory that could explain this difference in sperm quantity and behavior. According to the leader of the investigation, the most plausible thing would be to relate it to the “different levels of environmental exposure”. This means that both atmospheric pollution and other compounds could be behind the loss of semen quality. Neverthelessthese factors were not analyzed during the studyso they must continue investigating this hypothesis.
A hypothesis related to other previous studies
The origin of this line of thought is based on other studies that also revealed geographical differences regarding semen quality in different nations. Likewise, research carried out by the Institute of Environmental Diagnosis and Water Studies (IDAEA) of the Higher Council for Scientific Research (CSIC), in collaboration with the Rovira i Virgilli University, demonstrated in 2023 the presence of different contaminating and toxic compounds in some of the samples analyzed, which could have negative consequences on male reproductive health.
Therefore, it is essential to determine what factors have caused such great inequality between regions, as it could reveal key information about the effects that pollution is having on human beings, especially men. Well, it is worth remembering that semen quality is not only a determining factor for fertility, it is also an indicator of the individual’s health. This factor can also be a symptom of hormonal problems or high levels of stress.