While it may be tempting to finish "just one more" episode of that TV show you downloaded illegally, or read one more chapter of your e-book, research shows that using electronic devices before going to bed dramatically worsens your quality of sleep and alertness the following day.
The influx of smart phones, tablets, and other portable electronic devices has made us more prone to poor sleep habits, researchers say. The artificial light emitted by these devices signals our brain to stay awake, as it grows accustomed to thinking light equates to daytime. Our natural circadian rhythms become disjointed, and as a result, our brain produces less of the hormone melatonin, which is produced in the absence of light and helps regulate sleep.
"We think that the advent of electric lighting has significantly impacted upon sleep-wake patterns," Professor Shantha Rajaratnam, from Monash University's School of Psychology and Psychiatry, told ABC news. "But with the proliferation of electronic devices that emit light we are expecting that these problems will increase."
Such devices pose a greater threat depending on how close people use them to their eyes and the type of light emitted by the device, Rajaratnam said. Short wavelength blue light, the exact kind that backlit devices shine into the user's eye, represent the greatest hazard to getting a restful night's sleep. This is compounded through the brain's decreased secretion of melatonin.
The average electronic device emits a light that is half as intense as an ordinary room light.
"We know from preliminary reports that this level of light emission, 30 to 50 lux, is sufficient over a week or so to delay the timing of the circadian clock as well as suppress the production of the hormone melatonin," said Professor Rajaratnam. "We would recommend that these devices are shut down or closed off up to two hours before bed time, but at least one hour before bed time, to try to reduce the impact of these light sources on sleep."
Decreasing a device's brightness can help to keep melatonin secretion at more reasonable levels. Rajaratnam also said technology is being developed to filter out the most harmful wavelengths from the devices' light source.
EFFECTS CARRY INTO THE DAYTIME
Professor Rajaratnam isn't the only doctor with concerns over electronic device use before bed. Clinical psychologist Dr. Amanda Gamble has fears that much greater concerns lurk behind disrupting a simple night's sleep.
Because of the association many people create between their bed and using some sort of device — e.g. a phone as an alarm clock, a laptop as a television, or a tablet as a book — people begin to deprive their brain of the downtime that's necessary in the sleep process.
"We've gone from bigger devices - the computers that were fixed on our desk to the handheld portable devices ... so it's become a much more difficult issue to actually create a boundary between sleep and switching off these devices," she said, "because of course they come into the bedroom and a lot of people use their mobile phones as their alarm clock."
These effects create a group of people who likely do not label themselves as morning people. Charles Czeisler, Ph.D. and professor of sleep medicine at Harvard Medical School wrote recently that the extended use of electronic devices at night can result in a domino effect. The "second wind" feeling that people generally experience mid-day soon appears at nightfall.
"Before the widespread use of electric light, people probably experienced that second wind in the mid-afternoon, keeping them going until night fell," said Czeisler in a recent issue of Nature. "But light exposure after sunset signals 'daytime' to the [brain], shifting the clock later, postponing the second wind and delaying the onset of melatonin secretion. As a result, many people are still checking e-mail, doing homework or watching TV at midnight, with hardly a clue that it is the middle of the solar night."
KIDS, LISTEN UP
Especially disastrous is the potential impact in children, who need a proper night's sleep even more so than adults given their still-developing brains and increased need for concentration at school.
"Often young people are using these devices in the bed and this creates a learned association between the bed as being a place of study or work or socializing, rather than keeping the bed just for sleep," said Gamble. "They're at much greater risk of later developing anxiety disorders, depressive illnesses, substance abuse issues and also, on the more physical side, they're at increased risk of poor glycemic control, diabetes and so on."
Moving forward, Czeisler echoed Rajaratnam's sentiments regarding the phasing out of blue light-heavy devices before bed.
"The adverse effects of night-time light on sleep and circadian rhythms can be reduced by replacing blue-enriched light with red- or orange-enriched white light after sunset," said Czeisler. He concluded by encouraging the scientific community to reexamine what it knows about the effects of electricity on our brains.
"It is time to reassess the early assurances of Thomas Edison," he said, "that using electric light 'is in no way harmful to health, nor does it affect the soundness of sleep.'"