Study of a group of 484 fertile men Part II: Relation between age (20–59) and semen characteristics

Abstract

Commonly measured semen variables as well as post-thaw motility have been studied as a function of age in fertile men. The mean age was 34.6 (SD = 6.6). No significant change with age was found for the sperm count, semen volume or total number of spermatozoa. Conversely, there were significant differences between age groups for the percentage of normal cells (P less than 0.01) and the percentage of motile forms (P less than 0.01) as well as for the after-thaw motility (P less than 0.001). These three variables rise, reach a maximum level at 30 to 35 years of age and then decrease. These changes are not explained by variations in the length of abstinence.

Spatiotemporal trends in human semen quality

“…A US study 22 in 763 men showed 5th percentile thresholds of sperm concentration, total sperm count and percentage motility lower than the 2021 WHO references 67 (12 versus 16 × 10 6 /ml, 32 versus 39 × 10 6 and 28% versus 42%, respectively). Similarly, a Japanese study 31 in 792 men found a 5th centile threshold lower than the reference values 67 for seminal volume and normal sperm morphology (1.0 versus 1.4 ml and 1.5% versus 4%, respectively) whereas an Egyptian study 68 in 240 men reported a 5th centile for total sperm count notably lower than the reference values and percentage motility higher than reference values 62 (30 versus 39 × 10 6 and 50% versus 42%, respectively). By contrast, Chinese semen data collected in 1,213 men 69 did not reveal marked contrasts with reference data 67 .…”

“…That the processes of spermatogenesis and sperm maturation are simply not yet optimal in younger men emerging from adolescence cannot be ruled out, although only a few studies partly support this conclusion. For example, Schwartz et al 62 reported that the percentages of normal and motile spermatozoa peaked at 30–35 years in fertile candidates for sperm donation, and total sperm count was reported to increase markedly with age in a population of sperm donors in a separate study 63 , from a mean value of 263 × 10 6 in men aged 20 years to 431 × 10 6 in men aged 34 years. Seminal volume, total sperm count and sperm motility have also been reported to be lower in men <21 years old than in male partners aged 21–50 years in infertile couples 64 .…”

Age paternel et risques pour la descendance

“…Or c'est ce que I'on constate pour la morphologie et la mobilite des spermatozoTdes qui passent par un maximum, chez I'homme, aux alentours de la trentaine [42]. Puisqu'on sait que la morphologie du spermatozoTde est genetiquement determinee [10], une telle evolution suggere une amelioration des facteurs informatifs dans la partie ascendante de la courbe, et une degradation de ces facteurs dans la partie descendante.…”

Age paternel et descendance

“…Or, de ce point de vue, les travaux de Schwartz et coll. [5] sont tr6s r6v61ateurs. Analysant la num6ration, la morphologie et la mobilit6 des spermatozoides chez des hommes de 20 ~ 59 ans, ces auteurs montrent que si la num4ration est relativement stable les param6tres qualitatifs, au contraire, 6voluent en fonction de l'~ge : les valeurs sont maximales entre 25 et 35 ans, croissantes avant, d6crois-santes apr6s (figure 3).…”

“…Si toutefois on fait intervenir d6s maintenant l'hypoth6se g4n6tique, la forme de la courbe signifie qu'une am61ioration tr6s subtile pourrait caract6riser le g6nome du spermatozoYde/t partir de la pubert6, la qualit6 de celui-ci passant par un maximum autour de 30 ans, pour se d6grader ensuite. Or c'est, comme on l'a vu, ce que l'on constate pour les caract6res qualitatifs des spermatozoYdes qui passent par un maximum, chez l'homme, aux alentours de la trentaine [5]. Puisqu'on sait que la morphologie du spermatozo/de est g4n6tiquement d6ter-min6e [40], une telle 6volution sugg6re une am61ioration des facteurs informatifs dans la partie ascendante de la courbe, et une d4gra-dation de ces facteurs dans la partie descendante.…”