Dear Lifehacker, I like to use my smartphone and tablet in bed. I know that screen time before bed is bad for my sleep, but will features like Apple's Night Shift and Android N's Night Mode help me get better sleep and let me read in bed at the same time? Sincerely, Bedtime Browser
Let's start with what we know: ocular light exposure disrupts your body's natural ability to produce melatonin, a hormone produced by your pineal gland that helps you fall asleep. When you disrupt this process, your circadian rhythm (or "internal clock") gets thrown off. We're supposed to sleep in the dark, and unnatural light sources make it more difficult. In fact, according to one study, published in the Journal of Endocrinology & Metabolism, even the visually impaired have a similar response to diffuse light.
Smartphones and tablets have the same disruptive effect on your brain. Light can either advance or delay your circadian rhythm, and even the small amount of light being produced by your screen advances it (even in a dark room). Basically, your body thinks you're looking at sunlight (even if you consciously know it's night), and reacts accordingly. Countless studies (like the one mentioned above) have suggested that the type of bright, blue light emitted by your devices is especially disruptive because its short wavelength is what tells your brain to be alert, not at rest. In fact, one Swedish study, published in PLOS One, suggests that blue light may even be better than coffee at making people more alert.
Less Blue Light Before Bed Is a Good Thing
That's where features like Apple's newly-announced Night Shift and Android N's upcoming Night Mode come in. They automatically detect when it's getting close to your bedtime and reduce the brightness and adjust the colour temperature of your display to minimise the amount of blue light. This gives your screen a warmer, darker colour palette that may appear less crisp, but is much easier on the eyes. Ideally, you'll be able to look at your phone or tablet as much as you want because you're getting less light overall, and none of that problematic blue light.
The logic is sound on the surface. By removing the nasty blue stuff, you prevent your device from tricking your brain into thinking it's time to be awake and shutting down melatonin production. There's evidence to support it, too. Multiple studies suggest avoiding blue light at night with orange-tinted, blue-blocker glasses have a positive effect on sleeping patterns. For example, one study, published in the Journal of Adolescent Health, found that teenage boys were able to sleep better when wearing blue-blocker glasses before bed, and another study, published in Chronobiology International, had similar findings with adults. In the study, one group was given ultraviolet-blocking glasses, and the other group was given blue-blockers. The blue-blocking group reported an easier time falling asleep compared to the ultraviolet-blocking group (but it's important to note that, when compared to the teenager test, the adult participants' device usage before bed was significantly less to begin with).
Night Modes Reduce Blue Light (But It May Not Save Your Sleep)
However, what we don't know for sure is whether features like Night Shift and Night Mode will be enough, or have the same effect over the long term as the blue-blocking glasses do. There haven't been any long term studies on these features and their effect on people's sleep, or on apps like f.lux or Twilight, which many people use today for the same thing. We can assume that shifting the colour palette of your device's screen to warmer temperatures will reduce blue light exposure, thus helping you avoid the disruption of melatonin production and confusing your circadian rhythm, but we don't know for sure yet.
However, there have been studies that tested colour temperature and its effect on activity, drowsiness, and sleep quality. One study, published in the Journal of Physiological Anthropology and Applied Science, suggests that colour temperature is more important than illumination level when it comes to light's effect on your sleep. According to the study, low temperature lighting (warmer colours like red and orange) made participants drowsier and reduced their activity, despite the level of brightness (good news for your devices with night modes). A separate study, published in the same journal, suggests that colour temperature may also affect the quality of your sleep. Researchers found evidence that the presence of high colour temperatures (cooler colours like blue and white) before and during sleep negatively impacted the overall rest participants experienced during the trials. Unfortunately, both of these studies were very small (with only eight males in the first study and seven males in the second), so it's hard to say how it will all shake out when it comes to the millions of devices in people's hands.
Apple's Night Shift and Android's Night Mode certainly seem to be headed in the right direction. That said, they may not be the panacea Apple and Google make them out to be. Your devices are still going to emit some light, and while these features might make it easier to fall asleep on a physiological level, they can still distract you on a psychological level (especially if you keep getting notifications). If you want to use your device in bed, it certainly doesn't hurt to use them; they show a lot of promise. Just keep your expectations in check, and remember that there are a lot of other factors when it comes to getting decent sleep.
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