Sleep 19 - Action - Switch off all electronic screens at least an hour before going to sleep. 2 to 3 hours before bed are even better.

“The biological clock in healthy adults follows a 24-hour sleep-wake cycle. When the sun rises in the morning, your body produces cortisol, a hormone that makes you feel awake and alert. As daylight fades, the body releases another hormone, melatonin, that produces feelings of sleepiness.”

“Electronic back-lit devices like cell phones, tablets, readers, and computers emit short-wavelength enriched light, also known as blue light. Fluorescent and LED lights also emit blue light, which has been shown to reduce or delay the natural production of melatonin in the evening and decrease feelings of sleepiness. Blue light can also reduce the amount of time you spend in slow-wave and rapid-eye movement (REM) sleep, two stages of the sleep cycle that are vital for cognitive functioning.”

“Children are particularly vulnerable to sleep problems stemming from electronic devices that emit blue light. Numerous studies have established a link between using devices with screens before bed and increases in sleep latency, or the amount of time it takes someone to fall asleep. Additionally, children who use these devices at night often do not receive enough high-quality sleep and are more likely to feel tired the next day.”

Above quotes from "How Electronics Affect Sleep" by Danielle Pacheco, Staff Writer, and Kimberly Truong, Sleep Medicine Physician. SleepFoundation.org - https://www.sleepfoundation.org/how-sleep-works/how-electronics-affect-sleep