Semen characteristics as a function of age in 833 fertile men.

The relationship between age and semen characteristics has been studied; any effect due to the influence of the length of abstinence preceding ejaculation was eliminated. There is an improvement in semen characteristics up to 25 years of age, followed by a leveling off and a subsequent decrease. This variation is not significant as far as the sperm count, semen volume, and the total number of spermatozoa are concerned. The variation, although small, is highly significant for the morphologic characteristics and prefreeze and postthaw motility. The values for the older subjects were significantly lower for postthaw motility in the group 36 to 40 years of age, in the group 41 to 45 years of age for morphologic normality, and in the group 46 to 50 years of age for prefreeze motility. The lower values in the group 21 to 25 years of age are particularly noticeable with regard to morphologic characteristics. The same curve is encountered in the variation with age of each abnormal form, but the most marked variation is found in the increased percentage of coiled tails, which first appears in the group 36 to 40 years of age.