Greg Stanton, a reproductive biologist at the University of Lagos in Nigeria, reported a dramatic decline in male fertility and stated that this issue has been severely overlooked. According to a study in 2026, global sperm counts have decreased by more than 51 percent since 1973, and this trend is accelerating. Additionally, men are less likely than women to seek fertility testing.
Decline in Sperm Quality
In a study led by Stanton and published in the journal Scientific Reports in 2023, semen samples from over 17,000 men were analyzed. This research showed that the quality of sperm shape and size (known as sperm morphology) decreased by about 50 percent between 2010 and 2019. Furthermore, sperm motility (its swimming ability towards the egg) has also significantly declined. For example, in Nigeria, this decline was reported to be 87 percent during the same period.
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Reasons for Overlooking Male Fertility
Stanton explains that male fertility is often not reported accurately, which is why there is a lack of understanding of this issue. Male fertility depends on various factors including sperm shape, size, and motility, as well as concentration and count. These factors can be affected by health conditions. Male infertility can result from obesity, stress, lack of sleep, smoking, microplastics, and cannabis use.
Obesity, in particular, can affect the testes, where sperm and hormones like testosterone are produced. The testes function best at a temperature two degrees Celsius lower than body temperature. Excess fat can raise the temperature and negatively impact sperm.
Moreover, many men under 40 have no reason to check their fertility. While women receive a monthly signal for health checks through their menstrual cycle, men do not have these signals and only realize problems when they seek to conceive.
Rifat Bibi, a clinical biologist and director of an IVF lab in Pakistan, points out that about 80 percent of her cases are due to male factors, which is significantly higher than the previously assumed 50-50 ratio.
There are other factors in this area that are less talked about, such as the use of artificial testosterone or steroids. Many men seeking a muscular physique inadvertently suppress their sperm production by using steroids. While steroid use can enhance athletic performance, it has a negative impact on fertility.
If a man is tested earlier, his sperm count usually returns to normal within 6 to 12 months, but the later the problem is identified, the less likely improvement becomes.
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