Why We Sleep: Unlocking the Power of Sleep and Dreams

by Matthew Walker

melatonin helps regulate the timing of when sleep occurs by systemically signaling darkness throughout the organism. But melatonin has little influence on the generation of sleep itself:

Melatonin simply provides the official instruction to commence the event of sleep, but does not participate in the sleep race itself.

regardless of the amount of recovery opportunity, the brain never comes close to getting back all the sleep it has lost.

This brief descent from high-degree wakefulness to low-level alertness reflects an innate drive to be asleep and napping in the afternoon, and not working.

Heavy on not working

those that abandoned regular siestas went on to suffer a 37 percent increased risk of death from heart disease across the six-year period, relative to those who maintained regular daytime naps.