Sleep is essential to maintain a healthy body. People who regularly have an adequate amount of restful sleep live longer, have better health and are more productive during the day.
Sleep is the natural state of rest for the mind and body where consciousness is partially or completely lost, resulting in a decrease in body movements and responsiveness to external stimuli. Healthy sleep involves 4-5 cycles of brain-wave activity. Each cycle progresses through the various stages of sleep known as Non-REM sleep and REM sleep.
Non-REM sleep occurs in four stages:
Stage 1 is the transition from wakefulness to light sleep where a person can be easily awakened and usually lasts 5-10 minutes.
Stage 2 is the onset of sleep where all body and brain functions slow down. This stage comprises approximately 45% of the night’s sleep.
Stages 3 and 4 are considered to be deep sleep where a person becomes difficult to wake up. These stages are important for the body’s growth as well as for daily muscle repair and restoration of immune function – especially in children. These stages comprise approximately 25% of the night’s sleep.
This stage is characterized by periodic bursts of eye movement, occasional muscle twitches, rapid breathing, elevated heart rate and vivid dreams. Infants spend approximately 50% of their sleep time in REM sleep, adults are in REM about 20% and elderly people approximately 15%.
Each sleep cycle takes approximately 90-100 minutes. Therefore, an eight hour sleep time will consist of 4-5 sleep cycles but the length of each stage varies throughout each cycle during the night.
How Much Sleep Do You Need?
Infants usually require about 16-18 hours of sleep per day, while teenagers need about 9 hours per day on average. Most adults need about 7-9 hours of sleep per day. The amount of sleep a person needs cannot be controlled by the individual. A sleep deprived person will need a greater amount of sleep to compensate for their loss of sleep.
Alcohol consumption by a person who is sleep-deprived will have increased effects on the body. In contrast, the effects of sleep deprivation will be reduced by the use of caffeine but only for short periods.
Lack of sleep may result in decreased immune response, fatigue, increased pain perception, depression, inability to concentrate, impaired memory, poor judgment, and an increased risk of traffic accidents. The effect of 24 hours of sleep deprivation is comparable to a blood alcohol level of 0.1%.