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Sperm Counts Are on the Decline. Is the Human Race in Danger?

There's a lot the "sperm crisis" can tell us about men’s reproductive health.

By Nathaniel Scharping
May 1, 2021 5:00 PMMar 21, 2023 8:16 PM
Sperm Stock
(Credit: WHITE MARKERS/Shutterstock)


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In 2017, something fairly unprecedented happened in regards to male reproductive health: People actually started talking about it.

What kicked off the fracas was an alarming paper in the journal Human Reproduction Update claiming that men’s sperm counts were just half of what they once had been.The study was a meta-review of research looking at sperm counts over the past four decades, and it included 185 studies that encompassed more than 40,000 men. Between 1973 and 2011, the paper’s authors concluded, the men’s sperm counts fell by more than 50 percent. The trend wasn’t leveling off, either. The authors conclude that “research on the causes of this continuing decline is urgently needed,” a fairly intense rallying cry in the strait-laced world of academic publishing.

The paper kicked off a frenzy of media coverage on the so-called “sperm crisis,” with journalists asking whether we might someday soon find ourselves in Children of Men territory. The 2006 sci-fi thriller depicts a world where human reproduction has ceased entirely, with apocalyptic results.

On the surface, the parallels seemed apt, if not entirely justified. But the specter of a sperm crisis is certainly worrying. If the crisis is as dire as the 2017 paper suggests, we might hit a point where reproduction becomes difficult and then stops altogether. No babies, and soon there’d be no humans at all.

Counting on Sperm

Claims of a potentially catastrophic decline in sperm counts aren’t new. Most notably, a 1992 review paper found a similarly steep decline in sperm counts. That paper was met with heavy criticism based on critiques of the data included in the analysis. For example, the men sampled for such studies often don’t represent the broader population, and individual studies vary widely from each other in terms of when, where and how data is collected. Altogether, it makes picking out meaningful trends difficult.

Soon after the 2017 review paper appeared, other fertility experts began to weigh in. The professional consensus, thankfully, is a bit less alarmist. While there may be cause for concern when it comes to male reproductive health, we’re likely not facing the imminent decline of civilization.

Much of the criticism centers on the fact that there simply isn’t a reliable trove of data covering the past 40 years to draw from. Laboratory techniques have changed in the decades since sperm data has begun to be collected, and it’s resulted in datasets that don’t always line up. Though the study’s authors made a concerted effort to use quality data, it may not have been enough.

If we look to studies of male fertility, rather than sperm counts, the data appears more mixed. A 2010 review of fertility in men in the U.K., for example, found no evidence that infertility had increased overall. And even though some studies do indicate that infertility might be increasing, there could be other explanations. What seems like a rise in infertility may actually just be a result of couples choosing to have children later in life, when fertility is naturally lower. That holds for men just as much as for women. One study points out that fertility can be around a third lower in men over 40 compared to those under the age of 30.

Still, there is evidence that men’s sperm counts aren’t quite what they used to be. Other review studies using a similar methodology as the 2017 paper have also found declines in sperm counts in both Europe and Africa. Smaller and more specific studies of men’s sperm counts often indicate a general decrease in both quality and quantity, as well.

One recent study found that nighttime artificial light exposure was linked to a decrease in sperm counts, for example. Another indicated that fine particulate matter pollution impaired sperm quality in men.

Indeed, elements of our modern lifestyle have been blamed for decreasing sperm counts on a spectrum almost too broad to be useful, though definitive links are lacking. Possible culprits include: Processed meats, heated car seats, cell phones, ibuprofen, cannabis, paracetamol, tight underpants and more. And in a recent book, Shanna Swan, a co-author of the 2017 sperm count paper, puts the blame largely on the chemicals that we are exposed to every day of our lives.

Even COVID-19 has been blamed for interfering with men’s reproductive health. A few studies have suggested a link between a COVID-19 infection and poorer sperm health. The mechanisms for this vary: One study suggests it could stem from an elevated immune response during an infection, another blames increased stress for the drop in sperm quality.

Still, even if sperm levels have fallen off, that’s no guarantee they’ll drop all the way to zero, either. A milliliter of ejaculate contains hundreds of millions of sperm; a “low” sperm count is under 40 million per milliliter. Meanwhile, it just takes one to fertilize an egg. New techniques like intracytoplasmic sperm injection involve artificially placing a single sperm in a woman’s egg to kick off a pregnancy. Men could theoretically see a multi-million-fold reduction in their sperm count, and the human race would still carry on.

A Larger Problem

But the sperm crisis, real or not, does point to a larger issue. Men’s reproductive health, overall, isn’t exactly in great shape.

Levels of testicular cancer and other conditions like hypospadia (a birth defect where the opening of the urethra is on the bottom of the penis) and cryptorchidism (when one or both testicles fail to descend) have risen in recent years, according to fertility experts.

Recent evidence is showing that if certain chemicals cross from a mother’s bloodstream into a fetus at the wrong time, it can cause developmental issues in the reproductive system and beyond. Studies in rodents have found a range of reproductive issues arising from exposure to BPAs and phthalates, chemicals that mimic the hormone estrogen. Other studies have found elevated levels of the chemicals in humans, and have begun to tie early exposure to health problems later on in life. The same could go for agricultural pesticides, which can also disrupt the endocrine system, which produces hormones in our bodies. Even small amounts could be harmful.

Evidence of environmental hazards affecting male reproductive health points to another concern. If things like BPAs and fertilizers can affect our reproductive systems, it's likely they're impacting other things, too. In other words, the lesson of the sperm crisis is not that humanity may soon see a dearth of children, or that men should begin freezing their sperm. It’s that men’s reproductive health is worth caring about because it’s a sign of their health overall.

After all, what’s the use in reproducing if we can’t make sure that our children are healthy?

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