We all have a day-night cycle of about 24 hours called the circadian rhythm. It greatly influences when we sleep and the quantity and the quality of our sleep. The more stable and consistent our circadian rhythm is, the better our sleep. This cycle may be altered by the timing of various factors, including naps, bedtime, exercise, and especially exposure to light (from traveling across time zones to staring at that laptop in bed at night).
REM sleep occurs after the fourth stage of NREM sleep, with the first stage occurring about 90 minutes after you first fall asleep. The first period of REM lasts around ten minutes, and each stage lengthens until the final stage, which may last as long as an hour. Your brain activity is heightened during REM sleep, and you experience intense dreaming plus periods of muscle paralysis. As you age, you spend less time in REM sleep; adults spend about 20% of their sleep in REM, while infants spend about 50% of sleep in REM.
Get comfy in bed and try what's known as the "4-7-8" breathing exercise. "This technique is also known as 'The Relaxing Breath' and helps promote better sleep," Tramonte says. To do it, simply breathe in through your nose for a count of four, hold it for seven, then breathe out through your mouth for a count of eight. And just like that you'll be asleep.
Use a blue light filter on your device. The blue light emitted by smartphones and tablets can be a powerful sleep disruptor. It suppresses your body’s production of melatonin and throws your circadian rhythm off, making it harder to fall and stay asleep. Luckily, many smartphones these days have a “night shift” feature that adjusts the screen from cool (blue) to warm (yellow) light, which is less likely to keep you up past your bedtime. Likewise, there are apps you can run on your laptop or tablet that reduce blue light. Some popular ones are f.lux and Twilight.