'Countdown to Zero': Endocrine Disruptors and Worldwide Sperm Counts

Henry Rosevear, MD


August 19, 2021

In medical school, I remember thinking that telling a patient "You have cancer" would be the most professionally challenging phrase I would ever utter. And don't get me wrong — it certainly isn't easy; but compared with telling someone "You are infertile," it's a cakewalk.

Maybe it's because people "have" cancer and cancer is something you "fight." Or maybe because, unlike infertility, cancer has become a part of public life (think lapel pins and support groups) and is now easier to accept. On the other hand, someone "is" infertile. The condition is a source of embarrassment for the couple and is often hidden from society.

Here's another concerning point of contrast: While the overall rate of cancer death has declined since the early 1990s, infertility is increasing. Reports now show that 1 in 6 couples have problems conceiving and the use of assisted reproductive technologies is increasing by 5%-10% per year. Many theories exist to explain these trends, chief among them the rise in average maternal age and the increasing incidence of obesity, as well as various other male- and female-specific factors.

But interestingly, recent data suggest that the most male of all male-specific factors — total sperm count — may be specifically to blame.

According to a recent meta-analysis, the average total sperm count in men declined by 59.3% between 1973 and 2011. While these data certainly have limitations — including the exclusion of non-English publications, the reliance on total sperm count and not sperm motility, and the potential bias of those patients willing to give a semen sample —the overall trend nevertheless seems to be clearly downward. What's more concerning, if you believe the data presented, is that there does not appear to be a leveling off of the downward curve in total sperm count.

Think about that last statement. At the current rate of decline, the average sperm count will be zero in 2045. One of the lead authors on the meta-analysis, Hagai Levine, MD, MPH, goes so far as to state, "We should hope for the best and prepare for the worst."

As a matter of personal philosophy, I'm not a huge fan of end-of-the-world predictions because they tend not to come true (think Montanism back in the 2nd century; the 2012 Mayan calendar scare; or my personal favorite, the Prophet Hen of Leeds). On the other hand, the overall trend of decreased total sperm count in the English-speaking world seems to be true and it raises the interesting question of why.

According to the Mayo Clinic, causes of decreased sperm count include everything from anatomical factors (like varicoceles and ejaculatory issues) and lifestyle issues (such as recreational drugs, weight gain, and emotional stress) to environmental exposures (heavy metal or radiation). The senior author of the aforementioned meta-analysis, Shanna Swan, PhD, has championed another theory: the widespread exposure to endocrine-disrupting chemicals in everyday plastics.

It turns out that at least two chemicals used in the plastics industry, bisphenol A and phthalates, can mimic the effect of estrogen when ingested into the body. Even low levels of these chemicals in our bodies can lead to health problems.

Consider for a moment the presence of plastics in your life: the plastic wrappings on your food, plastic containers for shampoos and beauty products, and even the coatings of our oral supplements. A study by the CDC looked at the urine of people participating in the National Health and Nutrition Examination Survey and found detectable concentrations of both of these chemicals in nearly all participants.

In 2045, I intend to be retired. But in the meantime, I think we all need to be aware of the potential impact that various endocrine-disrupting chemicals could be having on humanity. We need more research. If indeed the connection between endocrine disruptors and decreased sperm count is borne out, changes in our environmental exposure to these chemicals need to be made.

Henry Rosevear, MD, is a private-practice urologist based in Colorado Springs, Colorado. He comes from a long line of doctors, but before entering medicine he served in the US Navy as an officer onboard the USS Pittsburgh, a fast-attack submarine based out of New London, Connecticut. During his time in the Navy, he served in two deployments to the Persian Gulf, including combat experience as part of Operation Iraqi Freedom.

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