The Night Shift feature in iOS 9.3 lets you adjust the color temperature of the display, shifting away from blue spectrums of light, in the putative interest of improving sleep. But Apple makes no promises. On its website, Apple notes, “Many studies have shown that exposure to bright blue light in the evening can affect your circadian rhythms and make it harder to fall asleep.” In iOS, the feature is explained with “This may help you get a better night’s sleep.”
In fact, this feature likely will have little or no effect on most people. Apple hasn’t misrepresented any of the science, but clinical work done to date doesn’t point a finger right at mobile devices or even larger displays. Night Shift also can’t remove enough blue to make a difference if that color is the culprit. And blue light may not be the trigger it’s been identified as. While researchers haven’t tested the new feature yet, several factors add up to at best a placebo effect and a reminder to power yourself down.
Apple might have done better to create something called Night Safe, an option that would countdown the moments until you’d be locked out of your hardware till morning except for emergencies or going through a tedious override process—a Do Not Disturb on reverse steroids.
Jumping to the chase, if you’re ready to crash: If you want to sleep better, the almost universal suggestion from both sleep and lighting researchers is to turn off any screen two hours before your planned bedtime. Some also recommend using warmer lighting throughout your house in sources you use in the later evening.
Why do you feel blue?
Our circadian rhythm, a biological cycle, regulates how our body functions and repairs itself, although it’s commonly associated with sleep and wakefulness. It’s roughly 24 hours for human beings, and our bodies use a number of cues to keep us on track. Getting out of sync can contribute to illness, obesity, diabetes, and even an increased risk of cancer.
Researchers have conducted studies over decades that isolate people from external cues to see what a natural cycle looks like, and how we sleep and wake. More recently, a lot of clinical and survey work has looked into measuring the effect of lighting: cycles of light and dark, light temperature, brightness, and other factors.
A discovery about 20 years ago helped make a connection, the limits of which are still being felt out. Many animals, including humans, produce the hormone melatonin across the circadian cycle, but it’s suppressed to low levels during natural waking hours. As it gets dark, that suppression abates, and melatonin production helps us become sleepy and remain asleep. (It has many other attributes, too, and other hormones have cycles that seem less tied to sleep.)
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