Geographic Disparities Emerge in Spanish Semen Quality Amidst Declining Fertility Trends

A recent study presented at the 42nd congress of the European Society of Human Reproduction and Embryology (ESHRE) has highlighted significant geographical variations in semen quality among Spanish men. The research, which analyzed 386 men across seven Spanish fertility clinics between 2024 and 2025, found that residents of northern Spain consistently demonstrated superior seminal parameters compared to those in central and southern regions.

This finding emerges against a backdrop of declining semen quality across Spain. Over the past 15 years, semen quality has fallen by 28%, and by 78% over the last two decades, a trend that continues. The study aimed to identify which regions were faring better amidst this decline.

Regional Differences Emerge

The study adjusted for variables such as body mass index, exercise, and consumption of alcohol, tobacco, and coffee. Despite these adjustments, men from northern Spain exhibited the highest seminal parameters. Specifically, residents of Asturias and Cantabria showed significantly better results than men from Madrid and the central peninsular area.

Asturias and Cantabria led in key metrics. The northern region reported a total count of mobile spermatozoa nearly double that of the central area, with an average of 94.35 million compared to 50.11 million. Furthermore, the northern region presented the highest average sperm concentration at 80.96 million/ml and sperm motility at 44.79%, outperforming the south (55.4%) and the center (53.4%).

Environmental Factors Suspected

Given that lifestyle factors like diet and substance consumption did not fully explain these geographical differences, researchers are pointing towards environmental factors. The leading hypothesis suggests that exposure to air pollution, a mixture of industrial and agricultural toxins, including endocrine disruptors found in plastics, pesticides, and everyday cosmetics, may be a significant contributor.

This pattern is not unique to Spain. Previous studies on fertile men in cities like Copenhagen, Paris, Edinburgh, and Turku, dating back to the early 2000s, also showed geographical variations. Finnish men, for instance, had higher sperm concentrations, while Danish men had lower values. Retrospective analyses of French donors also revealed significant intra-country differences, with northern regions often performing better.

Broader Implications for Male Fertility

While better semen quality does not guarantee pregnancy, it is closely linked to fertility. Below certain thresholds for concentration and motility, the probability of spontaneous conception decreases considerably. The World Health Organization defines reference values for semen quality based on concentration (millions of sperm per milliliter), ejaculate volume, percentage of mobile sperm, and normal morphology.

The study also touches upon the growing evidence of microplastics in human tissue and semen. A 2023 study found microplastics in both testicular tissue and semen samples, with sizes ranging from 20 to 100 microns. Polystyrene was found in testicles, while polyethylene and PVC were detected in semen, suggesting potential contamination pathways.

The researchers emphasize that the decline in male fertility is not solely attributable to individual behavior. The environment in which individuals live appears to play a more substantial role. A cocktail of chemicals, including bisphenol A, parabens, benzophenones, and phthalate metabolites, has been directly associated with significant reductions in sperm motility.

Therefore, the study suggests that areas like Asturias outperforming Madrid should not be a cause for celebration but rather a call to action. It highlights concerns regarding water quality, pesticide use, and the pervasive presence of chemicals in daily life. The findings underscore that the issue of male fertility decline is a complex public health problem with significant political, sanitary, and regulatory dimensions, extending beyond individual choices.

Key facts
| Factor | Finding |
|—|—|
| Study Focus | Geographical variations in semen quality in Spain |
| Leading Regions | Asturias and Cantabria (Northern Spain) |
| Areas with Lower Quality | Madrid and Central Spain |
| Suspected Cause | Environmental pollution and endocrine disruptors |
| Global Context | Similar patterns observed in other European countries |

Source: A la pregunta de qué español tiene el semen de mayor calidad, la respuesta está clara: no son los madrileños – Xataka: https://www.xataka.com/magnet/a-pregunta-que-espanol-tiene-semen-mayor-calidad-respuesta-esta-clara-no-madrilenos

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