Using a laptop the way its name suggests—on your lap—has long sparked concerns about male fertility due to crotch overheating. Even now, while many laptops run cooler than their predecessors, men planning to father children still need to be mindful of the risks, some experts say.
“Human males have testicles outside our bodies for a reason,” says Dr. Jesse N. Mills, an associate clinical professor of urology and director of The Men’s Clinic at UCLA. “Our testicles like to be at least two degrees cooler than the rest of our body, and anything that affects their temperature can affect fertility.”
The research linking fertility struggles to hot tubs, saunas and other sources of "scrotal hyperthermia"—or excessively toasty testicles—goes back decades. There’s a clear and negative link between regular exposure to heat and a man’s sperm count and quality.
“The heat factor is a well-known negative impact on fertility, so we wanted to know if scrotal temperature really increased with laptop use,” says Dr. Yefim Sheynkin, an associate professor of urology at SUNY Stony Brook who coauthored a 2005 study on laptops and the heat they generate. “We found that, with laptop use, scrotal temperature did increase quite significantly.” After an hour of use, scrotal temperature jumped about 5 degrees Fahrenheit.
The way men sit when using a laptop can make matters worse. In a follow-up study, Sheynkin and colleagues found that sitting with knees together effectively traps heat and can raise a man’s scrotal temperature even absent a laptop. “So there are two factors here: the heat produced by the laptop and the rising temperature from having the legs together,” he says. (This is bad news for men who assumed they were safe wedging a pillow or laptop pad underneath their computer.)
These and other studies have not linked laptop use to reduced fertility, and it’s not clear just how much heat a man can take before his ability to reproduce suffers. But spending an hour or two every night on the couch with a computer on your lap may affect the health and vitality of your sperm, says Sheynkin. “If a laptop is used every day, testicular temperature remains elevated almost all the time—there’s not enough time for it to go back to normal,” he says. ( If you're not worried about reproducing, rest easy. Sheynkin says there are no cancer risks or other health concerns associated with hot tubs, hot laptops or other sources of elevated testicle temps.)
But scrotal heating isn’t the only fertility concern with laptop use.
While the evidence is mixed, some research has linked the electromagnetic frequencies (EMF) produced by cellular devices—both laptops and smartphones—to potential reproductive challenges in men and women.
Ashok Agarwal, a professor of urology and director of the American Center for Reproductive Medicine at Cleveland Clinic, has exposed semen samples to cell-strength EMF in a lab setting. He found evidence of oxidative stress, as well as significant drops in sperm motility and viability.
Agarwal is quick to point out that evidence outside the lab is lacking, so any EMF-induced damage to sperm is controversial. “An impact could be there, but a lot of work needs to be done,” he says.
The same is true of EMF-related fertility issues in women. One hotly debated (and much-criticized) 2007 study found device-strength EMF could extend or otherwise mess with a female’s reproductive cycle—at least in mice. But follow-up studies of women have not turned up proof of harm.
A third laptop-related factor could also have an impact on fertility. “As we’re getting more technologically advanced, we’re growing more and more sedentary,” UCLA’s Mills says. “Exercise and activity increases sperms counts, so I think just sitting for long periods is inherently bad for fertility.” (Research has also linked regular physical activity in women to upticks in reproductive success.)
So close your laptop, hop off the couch and get moving. Or, at the very least, keep your computer on your desk (and off your thighs).