Sleep Need: How Much Sleep and What Kind?

The authors studied 29 healthy men who habitualy slept nocturnally for long or short periods. The short sleepers were efficient, hardworking, and somewhat hypomanic: the long sleepers tended to be anxious, depressed, and withdrawn. Both groups had similar slow-wave-sleep (SWS) time, but the long sleepers had twice as much D (REM) sleep. The authors suggest that there are two separate requirements—a relatively constant requirement for SWS and a requirement for D sleep that is related to the individual's personality and life style.