How Much Sleep Do We Really Need?

There are several findings on the effects of sleep. Some major factors that are not often considered when looking at the effects of sleep deprivation are that it may often coincide with stress. Many people who suffer from a lack of sleep may be under large amounts of stress. Another component not considered is the effects of having our circadian cycles disrupted by this lack of sleep. These are not to be considered the sole reasons for the side effects of sleep deprivation.

Studies have shown that those who participated in sleep deprivation experiments experienced three consistent side effects from sleep deprivation. The first is an increase in sleepiness. Secondly they experience a wide variety of mood disturbances. And third they perform poorly on tests of vigilance. Not only do subjects suffer from these three side effects but sleep deprivation studies have shown that after two to three days of sleep deprivation they commonly experience something known as microsleeps. A microsleep is a brief period of sleep that usually lasts about three seconds long in which the subjects' eyelids will droop and they will become less responsive to the stimuli around them. These microsleeps can be experienced while sitting or standing.

One of the most interesting results of sleep deprivation studies are that some have shown that sleep deprivation does not seem to have an effect on ones intricate cognitive function, motor skills, and physiological performance. However, while some studies have shown this to be the case others have shown that these are affected although the data for theses is not complete or compellingly documented.

Another interesting finding is that when someone experiences a consistent lack of sleep that a person' rapid eye movement (REM) sleep automatically adjusts. Basically the more sleep that is missed the body will fall into the REM sleep cycle more often. It seems as if the subjects' increase the amount of REM sleep to make up the lost amount of REM sleep experienced from sleep deprivation. This brings up the questions of whether this is indicative of the importance of the REM sleep cycle. There are three basic theories on why this may be: The first is that REM is necessary for mental health, the second that it is necessary for normal levels of motivation and the third that REM sleep is needed for the process of memories. None of these theories have produced enough substantial evidence that this is the case, however.

Interestingly enough the amount of sleep we actually need is much less than the 8 hours that has been recommended. For years we have heard that 8 hours of sleep will produce health and longevity however, a large groundbreaking study from Japan has changed the picture. The study eliminated people who were ill, suffered from depression or anxiety and included only healthy subjects. Following more than 100,000 subjects for a decade had shown that the lowest mortality rate had occurred for those who slept an average of 5 to 7 hours a night.

Another interesting fact about sleep is that one can function on very little sleep a day without adverse side effects when slowly changing sleep patterns, known as long term sleep reduction. The type of sleeping cycle chosen for long term sleep reduction affects how far one can cut back and still maintain normal levels of functioning. There are two cycles of sleeping. The first is known as the polyphasic cycle in which a person sleeps several times a day. The second is the monophasic cycle in which a person sleeps once day.

Leonardo da Vinci was rumored to keep a polyphasic sleep cycle taking four naps a day of only fifteen minute intervals, 1.5 hours a day, which enabled him to complete all of his accomplishments. Many studies have been able to replicate the success of this formula although it was found that most people needed four naps that were 25 minutes in duration to sustain mental alertness and avoid grogginess. It would seem in this case people are capable of maintaining less than 2 hours of sleep a day on this cycle, although long term health and mortality may suffer according to Japanese studies. In studies of long term sleep reduction based upon monophasic sleep cycles it seems that a person can reduce sleep to no less than an average of 5 hours before experiencing adverse effects.

Although studies of sleep deprivation have shown definite side effects on our mood, sleepiness and vigilance it has also shown that we tend to have the ability to increase our efficiency at sleeping when we experience periods of sleep deprivation. This proves that there seems to be no particular amount of needed sleep that is measurable. If sleep is reduced gradually many of the side effects are removed aside from that of general sleepiness. According to the data that has been collected through studies the belief that we need sleep to achieve a homeostasis is extremely hard to prove. Although it shows that we can function on very small amounts of sleep it does seem to suggest that we do need some amount of sleep no matter how small to function at maximum efficiency.

Sources:

Tamakoshi A; Ohno Y. Self-reported sleep duration as a predictor of all-cause mortality: results from the JACC study, Japan. SLEEP 2004;27(1):51-4.

Basics of Biopsychology, by John J. Pinel. Published by Allyn & Bacon. Copyright © 2007 by Pearson Education, Inc Claudio Stampi. (1992)Why We Nap: Evolution, Chronobiology, and Functions of Polyphasic and Ultrashort Sleep