Semen quality in Norwegian men over a 20-year period.

Semen parameters of 135 randomly selected men in 1966 were compared with semen analysis of 148 men in 1986 to assess whether semen characteristics had changed during the period. Both groups of men were of barren couples; median age was identical in the two groups (31 years). The semen analyses included volume, sperm density, and sperm morphology. Significant change over the time period was observed only for the percentage of normal morphology. This parameter deteriorated from 60% in 1966 to 41% in 1986 (median values; p less than .001). This study, like studies from other industrialized countries, indicates a decline in semen quality over the past decades.