Science of Sleep
Sleep is one of those things that you do quite regularly but never particularly think about.
If you attach an electroencephalograph (EEG) to a person's head, you can record the person's brainwave activity. An awake and relaxed person generates alpha waves, which are consistent up and down waves at about 10 cycles per second. An alert person generates beta waves, which oscillate about twice as fast.
During sleep, two slower patterns called theta waves and delta waves take over. Theta waves have oscillations in the range of 3.5 to 7 cycles per second, and delta waves have oscillations of less than 3.5 cycles per second.
As a person falls asleep and sleep deepens, the brainwave patterns slow down. The slower the brainwave patterns, the deeper the sleep - a person deep in delta wave sleep is hardest to wake up.
When sleep clinicians are measuring the quality of someone’s sleep they attach sensors to the head, eyes, chin and chest. The eye sensors can measure rapid eye movement (REM) and the chin sensor indicates muscle tone while the chest sensor measures breathing. It is only by using the information from the five sensors that you can tell what stage of sleep someone is in.
At several points during the night, rapid eye movement (REM) sleep occurs with most people experiencing three to five intervals of REM sleep per night. Brainwaves during this period speed up to awake levels. If you ever watch a person experiencing REM sleep, you will see their eyes flickering back and forth rapidly. Periods of sleep other than REM sleep are know as NREM (non-REM) sleep.
REM sleep is when you dream. If you wake up a person during REM sleep, the person can vividly recall dreams. If you wake up a person during NREM sleep, generally the person will not be dreaming. You need both REM and NREM sleep to get a good night's sleep. A normal person will spend about 25 percent of the night in REM sleep, and the rest in NREM.
Most adult people required seven to nine hours of sleep a night. This is an average, and it is also subjective. People should be getting enough sleep that they feel refreshed in the morning and are not ‘stuck to the bed’ and sleepy for the rest of the day. If someone is sleepy during the day and needing to take naps then they are not getting enough sleep.
Tthe amount of sleep you need decreases with age - it is more to do with the natural decay of the body. A newborn baby might sleep 20 hours a day and by the age of four, the average is 12 hours a day. When the aged of 10 is reached, the average falls to 10 hours a day while senior citizens can often get by with six or seven hours a day.