For couples trying to conceive, sometimes the journey can feel like a never-ending swim against the tide. A new study reveals one reason the process might have been so difficult: Apparently, many of those little swimmers are actually going missing, with today's sperm counts at roughly half of what they were almost 40 years ago.
The analysis of 185 academic studies, published in the journal Human Reproduction Update, found that among Western men (including North America, Europe, Australia and New Zealand), sperm concentration has declined 52 percent and sperm count has declined 59 percent between 1973 and 2011. That's a plunging rate of 1.4 percent per year for sperm concentration and 1.6 percent per year for sperm count. Sperm concentration means how many millions of sperm there are in each milliliter of fluid, and sperm count is sperm concentration multiplied by the total volume of ejaculate. On top of those scary statistics, there's no evidence of the numbers leveling off in recent years.
"The high proportion of men from Western countries with concentration below 40 million/ml is particularly concerning given the evidence that (sperm count) below this threshold is associated with a decreased monthly probability of conception," the report says.
The international team of researchers looked at studies including 42,935 male participants among 50 different countries who provided semen samples during that four-decade period. In comparison, they found no significant declines in sperm counts and sperm concentrations of men living in South America, Asia and Africa.
“It’s extremely worrisome," Dr. Shanna Swan, study author and professor of environmental medicine at the Icahn School of Medicine told NBC News. “For couples who are trying to conceive, this is a very severe problem and it’s difficult psychologically, but in the big scheme of things, this is also a major public health issue.”
The researchers didn't look specifically at why these declines are happening, but they have some ideas of what might be causing them.
One of the main speculations is that we're exposed to many chemicals we've never been exposed to before. Dr. Hagai, lead researcher of the study, told CNN that previous studies as well as his own have shown common chemicals like pesticides and fire retardants can increase or decrease production of certain hormones, which can then disrupt the hormone-making system, and which in turn can harm male reproductive system development and fertility potential.
Other explanations include other environmental factors like global warming, as temperature change is known to influence sperm counts, and lifestyle factors like smoking, stress and obesity.
What probably isn't affecting your sperm too much? Your smartphone and tight underwear.
“If those things were lowering sperm counts as drastically as some people think they are, we would use them as a contraceptives—but we don’t," Dr. Joseph Alukal, urologist and director of male reproductive health at NYU Langone Health, told NBC news.
So instead of ditching those tighty whities, experts suggest hopeful dads should maintain a healthy diet, exercise, refrain from smoking and sleep better to increase their chances. A 2015 study from Harvard found men who ate organic, pesticide-free produce had better sperm counts. And a 2013 study from Denmark shows the worse men slept, the poorer the quality of their semen. Men who had slept the poorest also had a 25 percent reduction in sperm count.
But before you start freaking out, talk to your doctor about fertility tests. Or if you're hoping to verify your sperm count in the privacy of your home, well, thank the app gods, because of course there's an app for that.