Yes, the sperm quality of older men is lower than in young males. This decrease in fertility is not so significant as in females, though. From the age of 40 onwards, a man's fertility starts diminishing. Investigations have shown that the sperm volume and the sperm count diminish as a man ages. The reduction occurs slowly, yet progressively. At the same time, the levels of oxidative stress tend to be higher.
The chances of the sperms developing some kind of genetic abnormality increase as well. However, a man can continue to be fertile, that is, capable of causing pregnancy in a fertile female at the age of 50, 60 or even 70. See also: Andropause or "male menopause".
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