What Is Sleep?
The purpose and mechanism of sleep is not fully clear. It is a recurring state where there is a suspension of sensory and motor activity, it involves either partial or total unconsciousness and most voluntary muscles are no longer active. This is contrast to someone who is awake in a resting state in that they can react to stimuli. During sleep the body is in a heightened anabolic state, growth and rejuvenation of the immune, nervous, skeletal and muscular systems is occurring at an accelerated rate. So far as it has been seen mammals, birds, and many reptiles, amphibians, and fish sleep. In humans regular is required for survival.
What is the optimum amount of sleep?
Generally adults sleep between 6 and 8 hours every day. However everyone has a different optimal level of sleep. Sleep is considered good when there is no feeling of sleepiness or dysfunction during the day. Sleep should occur in relation to the persons circadian rhythm and two major events need to occur to get a good nights sleep, there needs to be a maximum concentration of the hormone melatonin, and minimum core body temperature. A study by the University of California, San Diego, of more than a million adults found that the longest lived people are the ones who sleep for 6 to 7 hours. Other studies have shown that people who sleep more than 7 hours a day have an increased mortality. However it is unclear whether this effect is a cause or an effect as generally people who are depressed or of low socioeconomic status may be sleeping more. Also it has been implied that this lower sleep hours effect on mortality is only present when a the person is getting their optimal sleep rather than being woken up by an alarm.What are the effects of sleep deprivation?
The central health effects of sleep deprivation, are a doubling of the risk of death from cardiovascular disease, and also that too much sleep can also be associated with a doubling of the risk of death. Short sleep is a risk factor for gaining weight, type 2 diabetes and hypertension.