Sleeping for 7 to 9 hours at night isn't the only way to catch some z's. Here are four alternative sleep cycles -- and they're pretty obscure. Annie Miller Medical Reviewer Annie Miller is a licensed ...

As we sleep, our brain moves through four stages and two phases: non-rapid eye movement (NREM) and rapid eye movement (REM). The brain has four stages within the NREM phase. Each stage and phase of ...

Most experts recommend getting seven to nine hours of sleep a night — so why do we sometimes get a full night’s rest and still wake up feeling tired? It may have something to do with the point in the ...

You’ve probably heard the standard advice about getting eight hours of sleep. Maybe you even pride yourself on catching those full eight hours whenever possible—even if that means sleeping until noon ...

In general, most adults need between seven and nine hours of sleep per night. Someone who gets this recommended amount will generally go through between four and six sleep cycles (all of the sleep ...

Learn facts about sleep, during which the body rests, recuperates and performs essential repairs. When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works.