As difficult as it is to get kids to stop watching TV or using their electronic devices before bedtime, there’s a compelling reason to make it happen. The blue light that’s emitted from these screens can delay the release of sleep-inducing melatonin, increase alertness, and reset the body’s internal clock (or circadian rhythm ) to a later schedule. This is an especially big problem for teens whose circadian rhythms are already shifting naturally, causing them to feel awake later at night. The end result: sleep-deprived or poorly rested kids who have essentially given themselves a mini case of jet lag.
The reason that blue light is so problematic is that it has a short wavelength that affects levels of melatonin more than any other wavelength does. Light from fluorescent bulbs and LED lights can produce the same effect. Normally, the pineal gland in the brain begins to release melatonin a couple of hours before bedtime, and melatonin reaches its peak in the middle of the night. When people read on a blue light-emitting device (like a tablet, rather than from a printed book) in the evening, it takes them longer to fall asleep; plus, they tend to have less REM sleep (when dreams occur) and wake up feeling sleepier— even after eight hours of shuteye.
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