A new nationwide study has found substantial regional differences in sperm quality, with men in the highest-performing region recording almost double the total motile sperm count of those in the lowest-performing region.
Presented at the 42nd Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE), the study found that lifestyle habits were broadly similar across regions and did not explain the differences observed, raising important questions about the role of environmental exposures in male reproductive health.
The prospective multicentre study analysed semen quality and lifestyle data from 386 men undergoing fertility assessment across seven assisted reproduction centres in Spain between June 2024 and December 2025. Participants completed a standardised questionnaire covering factors including residence, body mass index (BMI), medical history, physical activity, chemical exposure, medication use, smoking, alcohol, drug and coffee consumption.
Researchers then compared semen parameters across four regions of Spain – north, south, southeast and central – to determine whether geographical differences in sperm quality could be explained by lifestyle or socio-demographic factors. The results revealed significant regional differences in semen volume, sperm concentration, motility, morphology and total motile sperm count, as well as the prevalence of asthenozoospermia (reduced sperm motility) and teratozoospermia (abnormal sperm morphology).
Men living in northern Spain recorded the strongest semen quality overall, with an average total motile sperm count of 94.35 million, compared with 50.11 million in central Spain. The northern region also had the highest average sperm concentration (80.96 million/ml) and sperm motility (44.79%). Reduced sperm motility affected 23.9% of men in the north, compared with 55.4% in southern Spain and 53.4% in central Spain.
Despite these differences in semen quality, lifestyle habits and overall lifestyle patterns were broadly similar across the four regions studied. After adjustment for all measured lifestyle and socio-demographic factors, only geographical location and abstinence duration remained independently associated with semen parameters.
“The strongest semen quality parameters were consistently found in northern Spain. We were surprised lifestyle habits were very similar across all geographical areas studied.”
Professor Rocío Núñez-Calonge, lead author
“Ruling out male lifestyle habits as the explanation for geographical differences in semen quality, variations may instead be related to differences in environmental exposure, such as pollution levels or environmental contaminants present in those areas.”
Professor Rocío Núñez-Calonge
Professor Núñez-Calonge noted that findings may have implications beyond Spain, with studies from several countries reporting significant regional variations in semen quality, particularly in areas with marked environmental heterogeneity.
“Given widespread air pollution in many urban environments, its potential effects on male fertility deserve further investigation. Larger well-designed studies are needed to clarify environmental exposure and semen quality relationships. Stronger public health policies aimed at reducing pollutant exposure should be considered a priority for protecting reproductive health in future generations.”
Professor Rocío Núñez-Calonge
“While healthy lifestyle positively affects sperm quality, environmental factors beyond individual control are evident and need addressing at societal and political levels. National and EU regulators bear clear responsibility.”
Professor Dr Karen Sermon, Immediate Past Chair of ESHRE
Journal: Human Reproduction