How Much Sleep Do Adults Need?
Each one of us has a unique sleep requirement. Our sleep need depends upon genetic and physiological factors and also varies by age, sex, and previous sleep amounts. However, a simple definition of sufficient sleep is a sleep duration that is followed by a spontaneous awakening and leaves one feeling refreshed and alert for the day.
Sleep Function and Need
Need for sleep is complex because it is bound up with the more general question of the function of sleep. As we do not understand the exact function of sleep, and it is possible that sleep serves many purposes, simple benchmarks for defining adequate sleep are difficult to identify. Normal individuals perceive that sleep is restorative. We know that deprivation of sleep makes us sleepy and results in poor performance while sufficient sleep improves our alertness, mood, and performance. Sleep may also provide significant long-term health benefits, but there may be many modifying factors such as the age of the individual, duration of sleep and influence of co-existing health problems and life-style and environmental factors. Determining the specific amount of sleep that is sufficient for optimal performance of a task is difficult since it may vary depending upon the task that is being performed, the time of day the task is performed, and the level of performance desired. To explore the relationship between sleep duration and important outcomes, most research has examined correlations between various sleep durations and levels of performance.
The relationship between sleep duration, performance and health is important and timely. Between 1959(1) and 1992(2) the average amount of sleep reported by middle age individuals decreased by about one hour per night (from 8-9 hours per night to 7-8 hours per night). A study examining the sleep duration from time diaries (records of sleep time and awake time) of full time workers from 1975 to 2006(3), found a significant increase in the number of individuals who were sleeping less than 6 hours per night. A recent study from the National Health Interview Survey which examined the sleep duration of individuals across several