What is 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.

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