Smartphones Disturb Sleep: Which Screens are Better?
Smartphones are sure convenient. But the more we use them, the more they can disturb our sleep. And we need sleep to stay healthy.
This is not good news for the surge of smartphone users. About two-thirds of Americans now use smartphones. And about 85 percent 18 to 29 year-olds old use a smartphone.
Screen testing with an app
These numbers led researchers from the University of California at San Francisco to study the effects of smartphone use on sleep.
The scientists tested 653 adults for one year – between 2014 and 2015. The subjects each downloaded a special application that measured their screen time and frequency. The application operated in the background. Every 30 days it would compile their screen use frequency, which was collected by the researchers. Those who had no screen time during the month were excluded from the results.
The participants were located throughout the United States, with a variety of occupations, ages and economic status.
Screen times recorded
The researchers calculated their results in 30-day windows. They found that people use their smartphones an average of 38.4 hours during a 30-day window. This netted out to an average of an hour and a half per day. Their daily use ranged from 53 minutes to 2 hours and 12 minutes.
Those with more screen time turned out to be younger. Females tended to have higher screen times, as did blacks, Hispanics and non-smokers. (I guess smokers wanted to smoke more.) More screen-time was not associated with income or physical activity. Neither was it related to higher BMI – like more television watching is. Obviously, people can stay active with their smartphones.
Another interesting statistic found in the study: Searching for medical information was the most common use for their smartphones.
Poor sleep with more screen time
Regardless, those who used their smartphones more also had significantly lower sleep quality. They also had shorter sleep duration, less sleep efficiency and longer sleep onset latency (getting to bed later).
Poor sleep and more screen time occurred among those who didn’t use their smartphones at bedtime. But the more the people used their smartphones at bedtime, the worse their sleep was.
Chalk it up to blue light
I discussed research on how bedtime computer and tablet use is linked to poor sleep in this article. I also discussed why this occurs: Blue light, which ranges from 380 to 500 nanometers in wavelength. As mentioned in that article: Computers, televisions, tablets and smartphones all emit lots of blue light.
Too much blue light affects our body’s circadian rhythms, along with our body’s production of melatonin. And because a reduction of melatonin supply has been linked to cancer, we can say that too much screen time can increase our cancer risk.
So does the sun’s rays as it collides with our atmosphere. In fact, blue light is what creates the blueness of the sky. But the sun’s rays also produce a number of other healthier wavelengths. These include UVB – which causes our bodies to produce the healthiest form of vitamin D.
What about E-Readers?
E-readers also emit blue light, due to their back-lit screens. A 2014 study tested 12 healthy young adults. They read either a E-reader or a printed book between 6pm and 10pm. They were given blood tests for melatonin levels. They also were also tested for sleep quality and tiredness in the morning.
The researchers found the E-readers reduced levels of melatonin and significantly disturbed sleep compared with the printed book readers. The E-reader users were also significantly more tired in the morning compared to the E-reader group.
Is Computer use worse than television?
This effect is also similar for television use. A study from Harvard tested 8,317 children from 138 elementary schools. They tested sleep levels against television use and video game use.
The researchers found that both television use and video game use at night significantly reduced sleep duration among the children.
This is consistent with the fact that most of today’s televisions and computers utilize back-lit screens.
Which screens are better?
The solution? Using our screens judiciously. We’re not just speaking of sleep here. These are electromagnetic devices that emit radiation after all. I discuss numerous strategies to combat the ill effects of EMFs in my book on the subject.
But certainly, screens are now an unavoidable part of our lives. So which screens are best and how should we use them?
Plasma screens, LED (light emitting diode) and LCD (liquid crystal display) screens work differently, but we are still left staring directly at beams of light that produce lots of blue light. Let’s review these along with some alternatives:
Most smartphones and computers use LCD technology, but newer computers and televisions can also be plasma screens. They tend to be more expensive however, and their size is typically limited by cost.
In a plasma screen, we are staring at tiny electronic lamps the size of pixels that are switched on or off. On-state pixels are thus tiny florescent lamps that shine into your eyes. When we are staring at a plasma screen, we are staring into numerous lights – just as we might stare at an array of fluorescent lights. Yes, we are staring into millions of tiny lights when we stare at our computer or phone screens. A larger plasma screen can have more than 6 million light cells.
In an LCD smartphone, computer or flatscreen TV, we are staring at liquid crystals that are polarizing beams of light. The light beams come from behind the screens. These are basically like fluorescent lights shining into our eyes. These beams of light are also called back lights. This why these devices are referred to as back-lit screens. As the light hits the liquid crystals, they will polarize the light into either a red, green or blue colors. Or the liquid crystal can block the light to create black.
The liquid crystals are each connected to a transistor, which modulates the polarity as the light shines through it.
Most LED TVs are also liquid crystal displays, but their back lights are LED lights instead of fluorescent. Their LED lights are also typically placed behind and around the liquid crystals. These allow for a flatter TV and possibly lower energy use. The plus is that you aren’t staring right into fluorescent lights in an LED TV. So there may be a slight reduction in blue light in LED screens compared to LCDs, but since both are backlit, they are both significant blue light emitters.
The newest organic LED screens (OLEDs) are different. These are not backlit. Instead of backlighting, these use individual OLED subpixels, which will display light through electron transfer through organic (carbon) based materials. The result is about a third less blue light than produced by LCD televisions. One test by LGD showed 3.1 times more blue light is emitted from LCD screens compared to OLED screens.
Another potential option, especially for night-time use, is the use of projectors. A projector will emit blue light just as a television will. But this light is reflected onto a wall, so it is not shining directly into the retina. The back lighting is being disbursed onto the wall rather than directly into your eyes.
This technique is also used to look at solar eclipses and other solar images. The harmful rays of the sun are being projected onto a secondary and not into the eyes. This removes their backlight effect.
For screens other than projectors, we should also employ our own background lighting. A mix of natural light in the room will help to prevent our eyes from fixating upon only the light coming out of our screens. In other words, looking at a computer screen in the dark is not such a good idea. Remember that the sun also produces blue light, but because there is a mix of spectra coming from the sun, the blue light portion is not as prominent. This is why natural light is the best fit for our eyes.
Discover: A tablet with its own projector
Christensen MA, Bettencourt L, Kaye L, Moturu ST, Nguyen KT, Olgin JE,Pletcher MJ, Marcus GM. Direct Measurements of Smartphone Screen-Time:Relationships with Demographics and Sleep. PLoS One. 2016 Nov 9;11(11):e0165331.doi: 10.1371/journal.pone.0165331.
Chang AM, Aeschbach D, Duffy JF, Czeisler CA. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proc Natl Acad Sci U S A. 2015 Jan 27;112(4):1232-7. doi: 10.1073/pnas.1418490112.
Taylor AW, Winefield H, Kettler L, Roberts R, Gill TK. A population study of 5 to 15 year olds: full time maternal employment not associated with high BMI. The importance of screen-based activity, reading for pleasure and sleep duration in children’s BMI. Matern Child Health J. 2012 Apr;16(3):587-99. doi: 10.1007/s10995-011-0792-y.
OLED versus Plasma Screens. Digital Trends