1.0 Introduction
As men advance in age, there are several changes that occur in their reproductive system. The changes particularly occur within the testes. The testicular mass decreases with aging. There is a decline in the levels of testosterone and as a consequence of the decline, men tend to have decreased libido and reduced number of spermatozoa. Aging in itself does not render a man sexually incompetent rather it presents several challenges to sexual performance. Some men develop erectile dysfunction although this may not necessarily be a direct consequence of aging. It may be caused by medications such as the ones used to treat hypertension or a pre-existing condition such as diabetes[ CITATION MHe99 \l 2057 ].
Enlargement of the prostate also occurs with aging resulting in the blockage of the urethra therefore increasing the incidences of urinary tract infections among older men. Incidences of prostate, bladder and testicular cancer are more common among older men than in younger men. It is a widely accepted fact that fertility in females generally declines with age as they advance towards menopause between the ages of 45 and 55. Men on the other hand have been known to retain their fertility even in advanced age. In fact, there is evidence to suggest that men can remain fertile till ages as advanced as 94.However due to the changes that occur in reproductive system, men are likely to become less fertile as they age or infertile[ CITATION Mco08 \l 2057 ].
2.0 Causes of Infertility in Older Men
Several changes in the reproductive system of the male subjects as they advance in age contribute to the increased incidences of infertility in older men. It is important to note that unlike women who experience sudden and definite change in fertility as they age men experience gradual change and it does not occur in all men[ CITATION Mco08 \l 2057 ].
There are trace amounts of reactive oxidative species (ROS) that are continuously secreted in the spermatozoa. While they play a pivotal role in hyper activation, motility, capacitating, acrosome reaction, and ultimately, normal fertilization; the increased secretion of ROS as one ages triggers an oxidative damage to the spermatozoa. Infertility incidences among older men have also been attributed to damage to the sperm DNA. There is a considerable breakage in sperm DNA as the male subjects advance in age and it has been established that there is an inverse relationship between DNA fragmentation index and male age by sperm chromatin structure assay .The increase in oxidative stress levels which are associated with aging might be responsible for this increase in DNA damage with age[ CITATION AJK08 \l 2057 ].
Another cause of infertility in men as they age is declining sperm count and a decline in sperm motility. The total sperm count is at its optimum between ages of 30 and 35 but above 55 years, it declines by 24.3%. Decline in sperm concentration is due to the effect of ROS on germ cell telomere and telomerase, while the decline in motility with aging can be attributed to the effect of ROS on sperm axonemal phosphorylation and lipid peroxidation[ CITATION AJu02 \l 2057 ].
Another cause of infertility is the reduction in testosterone with age. Testosterone levels could decline by as much as 50% between ages 20 and 80. The level of biologically available testosterone is reduced below the normal limit in 7% of men aged between 40 and 60 years, in 20% of men aged between 60– and 80 years, and 35% of men aged 80 years. This phenomenon is known as androgen decline in the aging male and has several manifestations: fatigue, depression, decreased libido, erectile dysfunction and reduced fertility[ CITATION MHe99 \l 2057 ].
In conclusion aging among males has been linked to various clinical consequences especially in the reproductive system. There is increasing evidence that the incidences of infertility among men increase with advancing age. The increased incidences of infertility in older men have been attributed to the increased secretion of ROS which in turn damages the spermatozoa and decreases sperm motility. The increasing sperm damage with age, decreasing sperm count and testosterone have also been blamed for the infertility incidences among older me.
REFERENCES
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Hermann, M., & Berger, P. (1999). Aging of the male endocrine system. Rev. Physiol Biochem Pharmacol , 89-122.
Jung, A., Schupe, H., & Schill, W. (2002). Comparison of semen quality in older and younger men attending andrology clinic. J. Andrology , 23-45.
Koppers, A., DeIuliis, G., & Finnie, J. (2008). Significancne of Mitochondria reactive oxygen species in the generation of oxidative stresss in spermatozoa. J Clin. Endocrinol Metab , 199-207.
