Many hormonal and non hormonal hypotheses have been put forward to explain a suspected decline in semen quality. We report on sperm parameter variation from the beginning of the eighties and the nineties in patients requesting an andrological clinical examination (1172 and 1393 respectively) and sperm bank donors selected by the same andrologists (17 and 21 donors, with 170 and 227 semen analyses respectively). We reduced bias to a minimum: all the semen analyses were carried out by the same biologist, using the same methods, the study groups were homogeneous for age, geographic-ethnic origin, residence, monthly-seasonal distribution and abstinence period.

Comparing patients from the 80s and the 90s, sperm concentration and motility showed a significant reduction. Furthermore, the decrease in concentration was mainly due to the age classes 26-30 and 31-35. The decline in motility was mainly due to the age class over 40 years. In donors, slight variations without a biological impact were observed. Our results indicate that subjects with higher levels of sperm production remain unaffected, while those with medium and lower levels are experiencing a real decline. This could mean that a selection is taking place in our country in favour of young, healthy, and highly fertile men.