How Using Electronic Devices at Night May Take a Toll on Sperm Quality

A new study links evening exposure to light-emitting digital devices to a decline in sperm and sleep quality.

Hormone disruption caused by late-night screen use may partly explain why male fertility has been on the decline, according to experts. 

The next time your guy tries to bring his smartphone or tablet into bed, you may want to discourage him from doing so — and not just because it kills the mood. A new study, shared at the Virtual SLEEP 2020 meeting, found a significant association between evening and late-night exposure to light-emitting digital devices and poor sperm quality.

The study examined 116 men, ages 21 to 59, who were undergoing evaluation at a fertility unit in Israel. After filling out detailed questionnaires about their demographic, health, and sleep variables as well as their daily exposure to digital media devices, the men were sent to a lab to have samples of their semen collected and analyzed within an hour.

It turned out that frequent evening use of digital devices was correlated with reduced sperm motility (the ability to “swim” properly) and reduced sperm concentration. In particular, smartphone use in the evening, tablet use after bedtime, and television use in the evening were all correlated with a decline in sperm concentration, according to the principal investigator, Amit Green, PhD, the head of research and development at the Sleep and Fatigue Institute at the Assuta Medical Center in Tel Aviv.

The study also found that men who had longer sleep duration tended to have a higher sperm total and better sperm motility, whereas those who reported greater sleepiness during the day had a reduction in total sperm number and the percentage of motile sperm.

Study May Explain Why Male Fertility Is on the Decline

The findings are especially significant because a study published in a 2017 issue of the journal Human Reproduction Update found that sperm count and sperm concentration declined by more than 50 percent between 1973 and 2011 among men in North America, Europe, Australia, and New Zealand. Ever since then, a search has been underway to pinpoint the environmental and lifestyle factors that may be contributing to this fertility-foiling phenomenon.

This new study from Israel suggests that the decline in sperm quality may be associated with evening and nighttime exposure to the short wavelength light (SWL) that’s emitted by the screens of digital devices. Previous research has shown that evening exposure to SWL — which is on the blue end of the spectrum — inhibits the secretion of melatonin, a hormone produced by the pineal gland in the brain that makes people feel sleepy and helps them stay asleep; as a result, exposure to the wrong forms of light in the evening can have a negative impact on sleep quality and quantity, for both men and women.

All of this is significant because, as the researchers in Israel note, “exposure to bright light has increased exponentially especially in the Western countries of the world due to unintentional exposure to illumination from electronic screens that emit light directly into the eyes.”

Potential Issues and Why More Research Is Needed

While the results of the current study are “provocative,” the study doesn’t distinguish between the effects of sleep duration and the effects of nighttime exposure to light on sperm, says Shanna Swan, PhD, an environmental and reproductive epidemiologist in the department of environmental medicine and public health at the Icahn School of Medicine at Mount Sinai in New York City. Another concern: “This was a specialized group of men at an infertility center, so I would be cautious about drawing conclusions about the general population from this study.”

Nevertheless, Dr. Swan adds, it’s clear that exposure to artificial light at night is an endocrine (hormone) disruptor because it affects melatonin, which is a hormone. Endocrine disruptors have been implicated as a likely contributor to the sperm count decline in the Western world, she says.

“To the best of our knowledge, this is the first study to report these types of correlations between sperm quality and exposure time to short-wavelength light emitted from digital media in the evening and after bedtime,” the researchers in Israel note.

Until more research is done to tease out what’s happening to the sperm of men who use digital devices at night, you and your honey may want to consider a digital curfew. “There’s no downside to stopping exposure to digital devices earlier in the evening, a few hours before bedtime,” Swan says. It’s a recommendation that falls into the can’t-hurt-might-help category for his future swimmers — and sleep quality for both of you.

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