Evidence for regional differences of semen quality among fertile French men. Fédération Francaise des Centres d'Etude et de Conservation des Oeufs et du Sperme humains.

The world literature on human semen quality indicates apparent geographical differences but these might primarily depend on variations among studies for subject recruitment strategy, semen analysis or data processing methods. A retrospective analysis on the quality of semen from 4710 healthy unselected fertile men, who were candidate semen donors to sperm banks in university hospitals in eight different French areas during the period 1973-1993, was undertaken. In these centres, all the men were referred under the same guidelines and all semen samples were analysed using similar methodologies. Significant differences were found between centres for seminal volume, sperm concentration, total number of spermatozoa in the ejaculate and percentage of motile spermatozoa (all P < 0.0001). Multiple regression analysis accounting for the age, sexual abstinence before semen collection and year of semen collection also showed regional differences: compared to Paris, the seminal volume was higher in Caen (P < 0.001) and lower in Toulouse (P < 0.01), the total number of spermatozoa was higher in Lille (P < 0.001) and lower in Toulouse (P < 0.05) and the percentage of motile spermatozoa was higher in Bordeaux and lower in Tours (both P < 0.001). This is the first study providing evidence for regional differences in the human semen quality.