Sperm output of older men.

BACKGROUND

Declining fertility of couples from the fourth decade of life is largely attributable to the drop in female fertility. However, increasing numbers of men, whose fertility theoretically lasts until death, are seeking fertility treatment at older ages, yet there is little information on sperm production and function past the age of 50 years. The few studies of such older men have examined men attending fertility clinics, and therefore willing to provide semen samples, but the participation bias of such recruitment hinders extrapolation to the unselected general male population.

METHODS

We have taken the opportunity to study a convenience sample of 55 healthy, non-infertile men ranging in age from 52 to 79 years old who provided semen samples as part of a prostate cancer screening project. They were compared with a control group (n = 409) of younger (< 52 years) men from among 567 volunteers screened as potential sperm donors for an artificial insemination program.

RESULTS

Older men had lower semen volume (mean semen volume 1.8 versus 3.2 ml; P < 0.0001) and total sperm output (median 74 versus 206 million sperm per ejaculate; P < 0.0001), whereas sperm density (median 64 versus 73 million sperm/ml; P = 0.12) was non-significantly decreased. Older men had more abnormal sperm morphology with decreasing numbers of normal forms (mean 14% versus 25%; P < 0.0001) and reduced vitality (mean 51% versus 80%; P < 0.0001), as well as increased numbers of cytoplasmic droplets (median 1 versus 0; P < 0.0001) and sperm tail abnormalities (30% versus 17%; P < 0.0001). Sperm head or neck abnormalities were no different between the groups.

CONCLUSIONS

While neither study group may be representative of the general male population, these findings suggest that sperm production, reflected in sperm output but not sperm density, as well as sperm morphology and viability are diminished in this population of healthy, non-infertile older men.