Most adults function best after 7-9 hours of sleep a night.
When we get less than 7 hours, we’re impaired (to degrees that vary from person to person). When sleep persistently falls below 6 hours per 24, we are at an increased risk of health problems
It's based on the idea that by partitioning your sleep into segments, you can get away with less of it.
Though it is possible to train oneself to sleep in spurts instead of a single nightly block, it does not seem possible to train oneself to need less sleep per 24-hour cycle.
Caffeine works primarily by blocking the action of a chemical called adenosine, which slows down our neural activity, allowing us to relax, rest, and sleep.
By interfering with it, caffeine cuts the brake lines of the brain’s alertness system. Eventually, if we don’t allow our body to relax, the buzz turns to anxiety.
Especially before bed. Phones and tablets emit light that’s skewed heavily toward the blue end of the visible spectrum and these frequencies are especially influential in human sleep cycles.
Using a “night mode,” available on some phones, is supposed to minimize that effect.
Melatonin is a hormone that regulates sleep-wake cycles.
Melatonin supplements have been shown to make some people fall asleep more quickly, but they aren’t proven to increase the total time or quality of sleep.