Dr. Ryan P. Smith, an associate professor of urology at the University of Virginia and specializing in male infertility, wrote in The Conversation that sperm quality has been declining for over 16 years, probably because of exposure to chemicals in the environment that causes imbalance to the hormone and adversely affects reproduction.
Infertility in the US
According to an article in the National Institutes of Health (NIH), nearly 1 out of 8 couples in the US struggle with infertility. Infertility is defined clinically as the failure to achieve pregnancy after one year of having unprotected intercourse. Studies show that 15% of couples are unable to conceive during their first year of unprotected sex, while 10% after two years.
Dr. Smith wrote that doctors could not determine the cause of male infertility around 30% to 50% of the time, although it is usually related to congenital, acquired, or idiopathic factors. More so, many health conditions could affect male fertility that could be treated through lifestyle changes.
The Decline in Male Fertility in the US
Men usually undergo semen analysis to assess sperm count or the total number of sperm a man produces and to check the sperm concentration to the number of sperm per milliliter of semen. These are standard measures but do not necessarily predict fertility in men.
The most reliable factor is measuring the total motile sperm count that evaluates the fraction of sperm that can swim and move.
Researchers starting in the 1900s noticed a concerning trend of male fertility wherein they observed that it has been declining for decades. Dr. Smith cited a 1992 study, titled "Evidence for Decreasing Quality of Semen During Past 50 Years" published in the British Medical Journal, wherein researchers found a global 50% decline in sperm counts in men.
Subsequent studies also confirmed the initial finding in which a 50% to 60% decline in sperm concentration was reported between 1973 and 2011 in men from around the world was reported.
Dr. Smith said that these studies show that a proportion of men with an average total motile sperm count had declined by 10% in the past 16 years. That means men today produce lesser sperm than in the past and they are less healthy.
What Caused the Decline in Sperm Quality?
Scientists point to toxic environmental exposure that can alter the hormonal balance and throw off reproduction. Dr. Smith and other researchers looked at the chemicals in the environment to identify the specific chemicals that cause the male fertility decline.
Multiple studies have shown that endocrine disrupters, such as phthalates, pesticides, herbicides, heavy metals, toxic gases, and other synthetic materials can disrupt the fragile hormonal balance of reproduction and adversely affects testosterone and semen health.
Herbicides and pesticides that are usually found in the food supply are known to negatively affect fertility, according to a paper in Toxicology Letters.
Moreover, studies have shown that air pollution that contains particulate matter can also contribute to abnormal sperm quality. Radiation exposure from laptops and gadgets is also associated with declining sperm count, impaired sperm motility, and odd sperm shape.
These compounds can take a significant toll on physical and emotional health, and treating these harms is costly.
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