The number of hours needed changes throughout your life, with babies and kids needing more sleep and people 65 and older able to function on slightly less than seven to nine hours. Here’s what ...

I spent days trying to understand what the charts and graphs were telling ... eight hours a night would require about 1.6 to two hours of sleep in REM sleep and the same amount in deep sleep.

'ZDNET Recommends': What exactly does it mean? ZDNET's recommendations are based on many hours of testing, research, and comparison shopping. We gather data from the best available sources ...