National Sleep Foundation

Chapter 1: Normal Sleep

Normal Sleep

The need for sleep varies between individuals and across the life span as we age. Normally, adults sleep about 7 to 9 hours per night although this varies considerably between individuals and with age; we spend one-quarter to one-third of our lives asleep.1  Sleep is not just the absence of wakefulness — rather, it is a complex and multi-dimensional state. Sleep influences all major systems of the body (see “The Physiology of Sleep”). And, this relationship is bi-directional, with many of body systems also influencing a person’s sleep. Sleep problems, including sleep deprivation can have a great deal of influence on one’s health, wellness, and longevity.


·         How Sleep Works: What Happens When You Sleep?



1.National Sleep Foundation (NSF), The Five Clusters of Sleep Patterns, Arlington: NSF, Available online at: