How much sleep do you need?

That depends. There are many factors, including:

• Age - See our page about sleep at different ages.
• Health - See our page about sleep disorders. General health can also affect the amount of sleep one needs. Sick people usually need more rest so their immune system can work better.
• Circadian Rhythm - Each person has his or her own biological clock that may respond differently to external stimuli than others. See our page about circadian rhythms.
• Body metabolism - Usually, the faster the metabolism, the more sleep needed.
• Physical exercise level - The quality of your sleep improves with exercise well before bedtime, often requiring less total sleep time.
• Gender - Women have the tendency to sleep longer than men. This may be related to need or it may be related to preference.
• The quality of your sleep - Although the average duration of sleep act as a good guideline, it does not tell us about the quality of sleep and the amount spent in various stages. This means that a person may feel very tired after nine hours of sleep, due to lack of REM and stage-4 sleep, and that another person may feel fresher after only six hours of sleep, thanks to a proportionally large amount of time which was spent in REM and Stage-4. The quality of sleep often depends on your health and your exercise patterns.
• Amount of sleep you've gotten recently - Sleep debt can lead to all sorts of problems if you don't stop to get the rest you need.
• Body temperature - Researchers have also found out that there is a strong relationship between the amount we sleep and our body temperature: Our tendency to fall asleep rises as our body temperature reaches its minimum and vice versa. Therefore, if we go to bed long before our body temperature reaches its minimum, our time asleep could result longer as we are further away from the time when our body temperature starts to rise again. (10)

The amount of sleep one needs definitely varies with the individual. Typically, eight hours a night is considered the average amount of sleep needed in a twenty-four hour cycle for a human adult. The best way to find out how much sleep you need is by trial and error. Find out how much you need in order to feel refreshed in the morning and to stay alert during the day on a regular basis.

Some people seem to get along fine with very little sleep at night. The video "Secrets of Sleep," reports on several individuals who lead productive lives with very little sleep (ranging from 1-5 hours a night) and the belief that their need for less sleep may be genetic. (1)

Edison vs. Einstein: Two Extremes

The two famous scientists Einstein and Edison had very different sleep patterns. (2). Thomas Edison is said to claimed sleep to be a waste of time. He did, however take naps during the day. Albert Einstein, on the other hand, was aware of his sleep needs, acknowledging that he needed ten hours of sleep for optimum performance.

This wide range of sleep needs appears natural. Researchers have determined there are two types of sleepers: the long sleepers and the short sleepers. Long sleepers need many hours of sleep, while short sleepers need a few hours less. By taking a closer look at both types of sleepers, it has been found that short sleepers spend a proportionally large amount of time in REM and Stage-4. Long sleepers, on the other hand, spend a proportionally large amount of time in stage 2 sleep.

Record Breakers

People have stayed awake for days in a row. In 1965, Randy Gardner stayed awake for 11 days, 12 minutes (3) In this experiment, Gardner did experience lack of coordination, hallucinations, blurred vision, muscle tremors, slurred speech, memory lapses, and concentration difficulties as a result of lack of sleep. (4) In 1980, Robert McDonald of California was reported to have stayed awake for a record 18 days 21 hours 40 minutes. (5) However, sleep deprivation is not something with which a person should experiment. It can be very dangerous to your health and the safety of you and those around you. Lack of sleep is not a light matter. Fatal Familial Insomnia is a rare disease that leads to death due to inability to sleep.

(1) "Secrets of Sleep." [Video recording] WGBH and BBC - TV. New York: Time-Life Multimedia, 1976.

(2) Information on Einstein & Edison's sleep patterns taken from

"Reviews and Commentary for Power Sleep : The Revolutionary Program That Prepares Your Mind for Peak Performance" [Excerpts from the book: "Power Sleep" by Dr. James B. Maas.] Last modified: May 15, 1999. Date viewed: July 17, 1999 URL: http://netmall.net/wishfuldrinking/sleepbook.html

(3) power sleep. p. 45

(4) sleep thieves, p. 50-54

(5) p. 29 encycl,

(6) Gerin, Sandrine. [Bien dormir c'est facile. Italian] "Dormire bene si può". Tranduzione di Maddalena Togliani. [Translated by Maddalena Togliani]. Milano, Nuova Pratiche Editrice, 1998, pp.22-27

(7) Dr. Manzel, Peter-Paul. "Gesunder Schlaf". Ed. Ratgeber Gesundheit. München, Mosaik Verlag, 1998, pp.16-19.

(8) Dr. Wenzel, Petra; Dr. Hanke, Günther and Dr. Uhl, Doris. "Nervosität und Schlafstörung- was tun?". Ed. Patienten-Beratung. Stuttgart, Medpharm Scientific Publishers, 1997, pp.11-15

(9) Hobson, J. Allan. [Sleep. German] "Schlaf: Gehirnaktivität im Ruhestand". Aus dem Amerikan. übers. von Ingrid Horn. [Translated by Ingrid Horn]. Heidelberg, Spektrum der Wissenschaft Verlagsgesellschaft mbH, 1990, pp.80-87, 90-101

(10) Dr. Manzel, Peter-Paul. "Gesunder Schlaf". Ed. Ratgeber Gesundheit. München, Mosaik Verlag, 1998, pp.16-19.