The Right Amount of Sleep

Sleep is a natural and normal state of bodily rest observed throughout the animal kingdom. It is a phenonemon that occurs in mammals and birds and also in many other species from the animal kingdom like many reptiles, amphibians, and aquatic creatures . In humans, other mammals, and a substantial majority of other animals which have been studied — such as fish, birds, ants, and fruit-flies, regular sleep is essential for survival. However, its purpose is only partly clear and is the subject of intense research.

What could be the right amount of sleep for a person at 40 years of age might not necessarily be the right amount of sleep for a two-month old baby.  The optimum amount of sleep is of lesser consequence if the timing of sleep is not right.  Hence the right amount of sleep should also be viewed in context to an individuals’ circadian rhythm.  It is therefore important to get the right amount of sleep during the right time.  The ideal conditions for the right amount sleep is when optimum concentration of hormone melatonin occurs and at minimum body temperature.

The National Sleep Foundation in the United States maintains that eight to nine hours of sleep for adult humans is optimal and that sufficient sleep benefits alertness, memory, problem solving skills, and overall health and at the same time reduces the risk of accidents.  A widely publicized 2003 study  performed at the University of Pennsylvania School of Medicine demonstrated that cognitive performance declines with fewer than eight hours of sleep.

However, the University of California, San Diego Psychiatry study of more than one million adults found that people who live the longest self-report sleeping for six to seven hours each night. Another study of sleep duration and mortality risk in women showed similar results. Other studies show that "sleeping more than 7 to 8 hours per day has been consistently associated with increased mortality", though this study suggests the cause is probably other factors such as depression and socio-economic status which would correlate statistically. It has been suggested that the correlation between lower sleep hours and reduced morbidity only occurs with those who wake after less sleep naturally, rather than those who use an alarm.

Causal links are currently speculative, the available data may only reflect comorbid depression, socioeconomic status, or even alcohol use.  These studies cannot be used to determine optimal sleep habits, they only establish a correlation — and empirically observed correlation is a necessity but not sufficient condition or grounds for causality.  A need for nine or ten hours of sleep a day, or only five to six, may or may not have the same cause as the shortened life span. In other words, long or short sleep duration by itself has not been shown to be a cause of early death.

Researchers from the University of Warwick and University College of London have found that lack of sleep can more than double the risk of death from cardiovascular disease, at the same time too much sleep can also double the risk of death. Professor Francesco Cappuccio said: “Short sleep has been projected to be a risk factor for weight gain, hypertension and Type 2 diabetes sometimes leading to mortality.  Therefore, while short sleep-mortality association has been established there are no potential mechanisms by which long sleep could be associated with increased mortality, or they haven’t yet been investigated. Some causes for this include depression, low socioeconomic status and cancer-related fatigue. In terms of prevention, our findings indicate that consistently sleeping around 7 hours per night is optimal for health and a sustained reduction may predispose a person to ill-health.”

Children need a greater amount of sleep per day when compared to adults in order to develop and function properly.  Newborns require up to 18 hours of sleep, with a declining rate as a child ages.  A newborn baby spends almost half of its sleep time in REM-sleep. By the age of five or so, only a bit over two hours are spent in REM.

As described earliery, if a person doesn’t get the right amount of sleep everyday consistently over a period of time, this sleep decifit will accumulate and this build up will translate to sleep debt.  Hence sleep debt is the effect of not getting enough rest and sleep; a large debt causes mental, emotional and physical fatigue. Scientists do not agree on how much sleep debt it is possible to accumulate, whether it is accumulated aginst an individual's average sleep or some other benchmark, nor on whether the prevalence of sleep debt among adults has changed appreciably in the industrialized world in recent decades. It is also likely that children are sleeping less than previously.

Even relatively modest daily reductions in sleep time (for example, one hour) can accumulate across days to cause a sleep debt. If the debt becomes too great, it can lead to problem sleepiness. Although the individual may not realize his or her sleepiness, the sleep debt can have powerful effects on daytime performance, thinking, and mood thereby affecting his or her health and also the quality of life.

Older people don’t need less sleep, but they oftenget less sleep. That’s because the ability to sleep for long periods of time and to get into the deep, restful stages of sleep decreases with age. Many older people have more fragile sleep and are more easily disturbed by light, noise, and pain than when younger. They are also more likely to have medical conditions that contribute to sleep problems.

Excessive daytime sleeping

Excessive daytime sleepiness can be associated with a sleep disorder or other medical conditions. Sleep disorders, including sleep apnea (that is, absence of breathing during sleep), insomnia, and narcolepsy, and may require behavioral, pharmacological, or even surgical interventions to relieve the symptoms. Extra sleep may not eliminate daytime sleepiness caused by these disorders.

Sleep deprivation and wakefulness

About 30 to 40 percent of adults indicate some degree of sleep loss within any given year, and about 10 to 15 percent indicate that their sleep loss is chronic or severe. In addition, millions of Americans experience problems sleeping because of undiagnosed sleep disorders or sleep deprivation.

Adolescents and shift workers are at very high risk of problem sleepiness due to sleep deprivation and the desynchronized timing of sleep and wakefulness, respectively. Sleep and wakefulness are linked in part to the activity of the circadian clock. Recent studies show that individual preferences for morning and evening activity may have a biological basis. In addition, studies show that adolescents experience a delay in the circadian timing system that results in a tendency for them to stay up later and sleep in later.

Loss of sleep creates an overwhelming and uncontrollable need to sleep and affects all physiological functions. Sleep loss causes problems with memory and attention, complex thought, motor responses to stimuli, performance in school or on the job, and controlling emotions. Sleep loss may also alter thermoregulation and increase the risk for various physical and mental disorders. Many adolescents are chronically sleep-deprived and hence at high risk of drowsy-driving crashes.

Sleep loss affects personal safety on the road. The National Highway Traffic Safety Administration has estimated that approximately 100,000 motor vehicle crashes each year result from a driver’s drowsiness or fatigue while at the wheel. Driving at night or in the early to mid afternoon increases the risk of a crash because those are times that our biological clocks make us sleepy. Drowsy driving impairs a driver’s reaction time, vigilance, and ability to make sound judgments. Many adolescents are chronically sleep-deprived and hence at high risk of drowsy-driving crashes. In one large study of fall-asleep crashes, over 50 percent occurred with drivers who are 25 years old or younger.

Excerpts taken from this article are licensed under the GNU Free Documentation License. They use material from Wikipedia topics "Lucid Dream" and/or "Sleep".