Dr. Teresa Larkin, a professor at the University of Wollongong, reported that the number of sperm in semen begins to decline gradually after the age of 20 and its average at the age of 55 approaches the threshold of infertility.
According to her, it's not just about the number of sperm, but also their quality. For pregnancy to occur successfully, the sperm must be alive, motile, and of a healthy shape. The volume of seminal fluid, which provides nourishment and transport for the reproductive cells, also plays a crucial role in this process.
Teresa Larkin says: "Starting around age 30, the proportion of normal-shaped, motile sperm decreases, semen volume decreases, and these changes become more pronounced after age 35."
She added that studies involving more than 2,000 couples showed that men over the age of 45 need, on average, five times longer to fertilize an egg compared to men under the age of 25.
It indicates that genetic damage accumulates in sex cells with age, as the stem cells that produce sperm divide hundreds of times during a man's lifetime, and with each division the risk of DNA errors increases, which may lead to the cessation of fetal development or miscarriage.
She explains: "According to studies, if a woman becomes pregnant by a man over the age of 40, the risk of miscarriage is about 30% higher compared to those under 29."
Also, after the age of thirty or forty, the incidence of chromosomal abnormalities that may cause congenital disorders, including Down syndrome and Klinefelter syndrome, increases.
According to her, external factors also affect male fertility. Oxidative stress—an increase in harmful compounds coupled with a deficiency of antioxidants—damages sperm DNA. This stress is exacerbated by air pollution, heavy metals, pesticides, smoking, alcohol abuse, obesity, and lack of physical activity. Varicocele—a treatable enlargement of the veins in the testicles—is also a common medical cause of infertility.
