The prospective multicentre study, which analyzed semen quality and lifestyle data from 386 men undergoing fertility assessments across seven assisted reproduction centers between June 2024 and December 2025, stratified participants into four distinct geographical zones: north, south, southeast, and central Spain. The results painted a picture of a stark reproductive gradient. Men living in the north recorded an average total motile sperm count of 94.35 million, a figure that vastly overshadowed the 50.11 million average found in the central region. This inferiority in the central and southern areas was not limited to sperm count alone; it was a systemic decline encompassing volume, concentration, motility, and morphology.

The severity of the dysfunction in the lower-performing regions is clinically significant. While only 23.9% of men in the north suffered from asthenozoospermia—a condition defined by reduced sperm motility—this pathology affected 55.4% of men in the south and 53.4% in the center. Furthermore, the prevalence of teratozoospermia, characterized by a high percentage of abnormally shaped sperm, followed a similar geographical pattern. This is critical because morphology and motility are essential biomechanical parameters; a spermatozoon requires a hydrodynamically efficient oval head and a vigorous flagellar beat to successfully traverse the female reproductive tract and penetrate the zona pellucida of the oocyte.

In an effort to disentangle the influence of personal behavior from location, participants completed standardized questionnaires cataloguing body mass index, medical history, physical activity, chemical exposure, and consumption of tobacco, alcohol, drugs, and coffee. When researchers adjusted the data for all measured lifestyle and socio-demographic confounders, the behavioral variables largely melted away in statistical significance. Only geographical location and the standard clinical variable of abstinence duration remained independently associated with the total motile sperm count and the prevalence of pathological motility and morphology.

This finding fundamentally shifts the etiological narrative. If heterogeneous lifestyle patterns cannot account for the geographic chasm, the mechanism of harm likely resides in the external environment. The study’s lead author, Professor Rocío Núñez-Calonge, a senior embryologist and scientific advisor to the UR Group, noted that the homogeneity of habits across the regions was surprising, making it implausible that the observed reproductive outcomes were self-inflicted. Instead, the data strongly implicate differential exposure to regional pollution gradients, industrial chemicals, or ubiquitous plastic-derived endocrine-disrupting compounds.

The biological plausibility of this environmental hypothesis is robust. Spermatogenesis is a highly sensitive process of continuous cellular division and differentiation that is particularly vulnerable to oxidative stress and hormonal perturbation. Environmental contaminants, including fine particulate matter (PM2.5) and phthalates, can cross the blood-testis barrier, inducing DNA fragmentation in germ cells and impairing Sertoli cell function. Professor Núñez-Calonge emphasized that the findings resonate beyond Iberian borders, aligning with prior multinational studies that document spatial heterogeneity in semen quality, particularly in regions marked by industrial activity or heavy air pollution.

The implications for public health policy are urgent. Professor Dr. Karen Sermon, Immediate Past Chair of ESHRE, reinforced that while individual lifestyle optimization is beneficial, the effect of involuntary environmental exposures has become undeniable. She stressed that these systemic threats to fertility cannot be solved at the clinical bedside alone but require intervention at the societal, national, and EU regulatory level. Given the trajectory of global urbanization, the research underscores a need for deeper investigation into the transgenerational reproductive toxicity of modern pollution, framing declining sperm counts not just as a biomarker of male health, but as a sentinel indicator of environmental degradation.

Subject of Research: Geographical differences in sperm quality and the influence of lifestyle versus environmental factors.
Article Title: Does male lifestyle influence geographical differences in sperm parameters?
News Publication Date: Presented at the 42nd Annual Meeting of ESHRE, 2026.
Web References: https://www.eshre.eu/
References: Núñez-Calonge, R., et al. (2026). Human Reproduction.
Image Credits: N/A
Keywords: Infertility, Sperm, Semen, Environmental Health, Air Pollution, Human Reproduction, Environmental Policy.