Myth and reality of the decline in semen quality: An example of the relativity of data interpretation

Many hypotheses have been put forward to explain a suspected decline in sem en quality. Up to now many sources of data were used but conflicting result s are present in the literature. To study whether modifications of sperm pa rameters actually exist we used data from two groups of patients checked an d two small groups of sperm bank donors selected at the beginning '80s and '90s. We tried to reduce bias to a minimum: all the semen analyses were car ried out by the same biologist, using the same methods, groups were clinica lly evaluated by the same andrological team, the study groups were homogene ous for age, geographic-ethnic origin, residence, monthly-seasonal distribu tion and abstinence period. Comparing patients from the '80s and the '90s, sperm concentration and motility showed a significant reduction. Furthermor e, the decrease in concentration and motitity was mainly due to the higher age classes. In donors, no decline was observed. These results seem to indi cate that sperm donors remain unaffected, while patients with lower levels of semen quality are experiencing a real decline. Unfortunately, many confo unding variables, analyzed in detail in this review, still remain despite e fforts at standardization. (C)2000, Editrice Kurtis.