Is Our Sleep Affected by Smartphones?

What are the effects of cell phone radiation on sleep quantity and quality?

“Sleep is crucial to the development of physically and psychologically healthy children,” but a number of factors have been identified as interfering with sufficient sleep, including the use of electronic media devices. These days, most children and nearly all adolescents have at least one such device “in their sleep environment, with most used near bedtime.” Such use is associated with “inadequate sleep quantity, poor sleep quality, with excessive daytime sleepiness.” There are calls to minimize access to these devices at bedtime, but “which comes first, media use or sleep problem?” Are the kids and teens not sleeping because they’re on their phone, or are they on their phone because they can’t sleep? I discuss this in my video Friday Favorites: Do Mobile Phones Affect Sleep?.

“Higher media use has been consistently associated with more irregular sleep patterns, shorter sleep duration, as well as more sleep problems.” Are we pushing back our bedtime because we’re so caught up in whatever we’re reading, writing, watching, or playing, or does using our devices key us up so we have trouble falling asleep? In college-aged students, it may be more of the reverse—not sleeping leading to pulling out their screens rather than just staring at the ceiling. In early childhood, though, it may be a bit of both. How might screen time interfere with sleep?

Use of smartphones and tablets may not just push back bedtimes and overstimulate us. The “light emitted from devices affects circadian timing” by interfering with the production of melatonin, the sleepiness hormone that starts ramping up as soon as the sun goes down. When we put a screen in front of our face, the excess light at night may confuse our brain. Of course, if you’re checking email with the lights on, then you’re already overexposed and the little bit of extra light from the screen may not make much difference. But, if you’re in the dark and need to send off that final message, then adjusting the light settings on your screen to be more yellow may help.

What about the cell phone radiation? Might leaving your phone on the nightstand somehow affect your sleep? There’s an enzyme called ß-trace protein that makes a sleep-promoting neurohormone in the brain, and researchers found that those with greater long-term exposure to cell phones or cordless phones tended to have lower levels of this enzyme in their bloodstream. So, the thinking is that the “emissions from wireless phones affect the release of ß-trace protein in the brain,” especially from the tissues right up under the skull, closest to where we typically hold the phone. So, there is a possible mechanism if cell phones do indeed affect sleep, but you simply don’t know until you put to the test.

Study participants were exposed to 30 minutes of a cell phone in talk, listen, standby, or off modes. All of the lights and speakers were disabled, and insulation was used to prevent them from feeling if the device was heating up, so the participants didn’t know which group they were in. After the exposure, researchers took away the phones, shut off the lights, and told participants to close their eyes and try to fall asleep. As you can see in the graph below and at 2:59 in my video, those exposed to the phone when it was off or in listen or standby mode fell asleep within about 20 to 30 minutes, but after being exposed to the same phone in talk mode, it took closer to 50 minutes on average to fall asleep.

The reason for the significant difference between talking and listening might be because the typical SAR value—that is, the specific absorption rate of how much cell phone energy your body absorbs—is about nine times higher when you’re talking than when you’re just listening to someone else talk.

When you do finally get to sleep, though, what are the effects of cell phone exposure on sleep quality? There have been about 20 studies, and they’re split about half and half in terms of whether cell phone exposure affected sleep parameters—and not all in a negative way. It reminds me of the brain function data. (See Do Mobile Phones Affect Brain Function? for more on this.) Yes, an increase in the excitability in our brain cortex, the outer layer of our brain, in response to exposure to cell phone emissions might disrupt sleep, but that increased excitability may also mean faster reaction times.

Similarly, in affected study subjects, those exposed to an active cell phone showed significantly more R sleep. But R stands for REM, so participants got about 4 percent more potential dream time, which isn’t not necessarily a bad thing.