Why Do Men Have Fewer Sperm Than They Did 50 Years Ago?

There’s a lot to like about sperm. They’re driven, goal-oriented, and hey, they’re responsible for half of your genetic material.

That’s why it’s so disconcerting that these little dudes are dying off in droves. The total male sperm count has decreased by about half since the 1950s, according to a large study that came out in the early '90s, which showed sperm counts had decreased from 113 million sperm per mL to 66 million sperm per mL over the course of 52 years. Though that study was critiqued, an analysis from a decade later reached similar conclusions, and the World Health Organization even lowered the numbers for what’s considered a “normal” sperm count in 2010, from 20 million per mL to 15 million sperm per mL.

What’s going on here? Could there really be a massive sperm extinction taking place right under our noses?

OK, several words, one of which is plastics, but all of which are about the increasing role chemicals have played in post-WWII life. Dr. Armando Hernandez-Rey, a reproductive endocrinology and infertility specialist at Conceptions Florida, believes sperm count is on the decline thanks in part to these environmental factors. “These include food and environmental toxins like preservatives, BPA, and similar chemicals found in plastics, fire retardants used in furniture, and many others,” he says. He's not the only one to suspect these endocrine-disrupting substances could help explain the decline in male fertility.

So, wow, that’s a lot of stuff to avoid if you're trying to SOS (save our sperm). It gets worse though: even the sun, the life-giving king of the sky, can drive sperm decline via ambient radiation, Dr. Hernandez-Rey adds, and the older you are, the more the effects have accumulated.

Basically, you have to become a cave-dwelling, root-scavenging hermit and your sperm will be fruitful and multiply. Good luck finding a sexual partner if you go that route.

Steroids and cocaine may make for a crazy night out, but they’re terrible for sperm. “Cocaine use in particular is surprisingly prevalent and closely associated with both low sperm counts and poor sperm motility,” warns Dr. Hernandez-Rey.

Coke and 'roids aren't the only drugs that may negatively impact male fertility. Opioid addiction and overdose deaths have increased 400% in the past 15 years, according to the Centers for Disease Control. Exercise physiologist Dr. Scott Weiss says many of his patients are long-term opioid users, and he doesn't think it's unreasonable to believe long-term opioid use and abuse might affect fertility.

“I have patients with severe back pain who have been on opioids for a year,” says Dr. Weiss. “There’s a decrease in testosterone, libido, and fertility goes after that. I think that is the link to the drop in fertility, but I would say this is more by observation.”

Legal drugs aren’t off the hook. Alcohol is known to screw with sperm, as do cigarettes. Even diets high in sugar could slow down your swimmers; same for eating too much saturated fat. While it's important to note that most of these studies are associations that don't definitively prove causality, it shouldn't be much of a surprise that not smoking, drinking less, and eating healthy can only help your sperm.

A 2015 study suggested a link between cellphone use and sperm concentration, which would be bad news for pretty much everyone. “Many studies in a number of countries confirm that cellphones can damage sperm,” says Dr. Devra Davis, visiting professor at Hebrew University Hadassah Medical Center and Ondokuz Mayis University Medical School. “As Consumer Reportsrecommended... nobody should keep a phone in their pocket, because doing so exceeds the as-tested exposure guidelines.”

Laptops are also a sperm killer -- not because of radiation but because of heat. “Testicles are outside the body in order to keep sperm slightly cooler than your body temperature,” Dr. Hernandez-Rey notes. “A less common but easily correctable cause can be prolonged heat from... laptops placed right on your lap.” So put a pillow under your laptop and move your cell phone to your back pocket. “Distance is your friend,” Davis adds.

Along the same lines, avoid hot tubs as well, and relish the fact that a ’roided up, hot-tubbing drug lord probably has fewer sperm than you.

If our collective sperm counts continue to decrease, won’t that mean the end of humans and the rise of a humanoid sex robot civilization? Well, maybe... but much of the evidence for a global sperm decline comes from sperm banks, where employees are finding that more modern-day “donations” aren’t as, uh, potent as those in the past.

“There have been studies by sperm banks looking at the average sperm counts of then and now, and they’ve noticed in some parts of the world, the sperm count of healthy donors has gotten lower than average,” says Dr. Philip Werthman, a urologist and director of the Center for Male Reproductive Medicine and Vasectomy Reversal.

The declining sperm count thing is pretty controversial, though. While that first study in the early '90s sounded the semen alarm, it was followed by an analysis pointing out its flaws... THAT was followed by a study confirming the ORIGINAL study.

It's almost impossible to account for confounding variables; for example, sperm donors aren’t necessarily representative of the whole population. (It takes a special sort of person to jizz in a cup for money, after all.) Or maybe doctors simply know more about sperm now. “Some of it is just that we are performing more semen analyses... and seeing more of these issues,” Dr. Hernandez-Rey says.

The doctors agreed that while it’s not time to freak out about declining sperm counts just yet, it’s definitely an issue to monitor. Dr. Werthman says one unexpected benefit this discussion is that it emphasizes male fertility.

"If people are having trouble getting pregnant, they need to pay attention to the male," Dr. Werthman points out. "People get treated on the woman's side, instead of addressing why there’s bad sperm and getting to the root of the problem." Placing responsibility for fertility solely in the hands of the woman, if you think about it, is pretty ridiculous to begin with.

Another plus: people do have a great deal of of power when it comes to halting the mass death of innocent sperm. “Many lifestyle factors that cause low sperm counts can be somewhat reversed if patients stop using drugs and smoking,” Dr. Hernandez-Rey says.

Just in case you needed another reason to quit.

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Missy Wilkinson wrote the word “sperm” so many times she thought she’d spelled it wrong, even when she hadn’t. Follow and/or heckle her on Twitter.