Problems in male factor fertility may be due to changes in semen quality as assessed by the semen analysis. The most significant of these are a low sperm concentration (oligospermia), poor sperm motility (asthenospermia), and abnormal sperm morphology (teratospermia). Other factors less well associated with infertility include semen volume and other seminal markers of epididymal, prostatic, and seminal vesicle function. As men age, these variables are impacted and correlate with decreased fertility. Sperm Concentration In 1969, Sasano and Ichijo first described the decrease Inhibitors,research,lifescience,medical in sperm concentration
as men age. They reported that 90% of seminiferous tubules in men in their 20s and 30s contained spermatids, whereas men in their 40s and 50s had
spermatids in 50% of their seminiferous tubules. Only 10% of seminiferous tubules from men aged > 80 years contained spermatids.17 However, recent publications indicate that, of all the sperm parameters, Inhibitors,research,lifescience,medical changes in sperm concentration with advancing male age are the least consistent.18–20 There are studies that report a decrease in sperm concentration of up to 3.3% per year of age,21 but other data report no change in sperm concentration up to age 50.22 Some have even suggested increases in sperm concentrations with age. A study of 20,411 men found a statistically significant increase in concentration of 0.7% per year of Inhibitors,research,lifescience,medical age. This amounts to an increase in concentration of 14% over a 20-year period.23 Inhibitors,research,lifescience,medical In a study of 1283 men who cryobanked sperm
prior to vasectomy, sperm concentrations were found to be lower at both extremes of age as compared with men aged 26 to 45 years.24 Motility In contrast to concentration, evidence consistently indicates that sperm motility decreases with advancing age. Studies that adjusted for duration of abstinence revealed statistically significant decreases in motility of 0.17% to 0.6% decrease per year of age21,24 Inhibitors,research,lifescience,medical resulting in a 3% to 12% decline in motility over 20 years. More recently, Sloter and colleagues used Thiamine-diphosphate kinase computer-assisted semen analysis in a population of 90 men aged 22 to 80 years with no history of infertility. Motility decreased 0.8% per year of age and linear motion decreased 0.2% per year.25 Because motility is acquired during sperm transit through the prostate and the epididymis, the decrease in motility is suspected to be due to MK0457 age-related decline in the function of these posttesticular glands.12 Age-dependent alterations of the epididymis may also cause alterations in sperm mitochondrial functioning, which is paramount for sperm motility.26 Morphology Similar to motility, morphology appears to decrease with advancing male age. Studies indicate declines in normal sperm morphology of 0.2% to 0.9% per year of age, resulting in a 4% to 18% decrease in normal morphology over a 20-year period.