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Sleep’s age-old mysteries have intrigued scientists and researchers for centuries. As sleep overtakes us and different parts of the cerebral cortex stop communicating, consciousness fades (Massimini et al 2005). Once asleep, we pass through a cycle of five distinct sleep stages at intervals of about every ninety minutes. Breathing becomes slow and regular, the pulse rate slows down, and the body temperature drops. Sleep activity is measured by electroencephalograph or EEG.
Stage 1 Sleep
As you enter light sleep (Stage 1 Sleep) the heart rate drops further. The muscles in your body relax and breathing bcomes more irregular. This may cause an occasional muscle jerk, called a hypnic jerk. Peope awakened at this time might say they were not sleeping.
Stage 2 Sleep
Sleep spindles form on the EEG charts during stage 2 sleep. After 4 minutes of the spindles appearing most people, if awakened, would say they were asleep.
Stage 3 Sleep
During stage 3 sleep, a new brain wave appers on the EEG chart called delta waves. These waves are very large and slow. They indicate a further loss of consciousness and a move to even deeper sleep.
Stage 4 Sleep
Typically after an hour, most people reach the deepest level of normal sleep – level 4 sleep. Delta wave patterns are long and slow and the sleeper is in a state of oblivion. If the person were to wake up, they would be in a state of confusion and may not remember being woken up. Sleep patterns will cycle though all 4 sleep stages throughout the night.
REM and NREM
The two most basic states of sleep are REM sleep (rapid eye movement) with associated dreaming, which occurs during all 4 sleep stages, and Non-REM (NREM) sleep that is dream-free. 90 percent of the time time, the early patterns of stage 1 sleep will lack REM and dreams.
REM sleep is a time of high emotion. The heart beat and blood pressure waver. Both males and females appear to be sexually aroused, and dream activity is at its height.
Sleep and Long Life
Obviously we need sleep. Lack of sleep is very harmful. We spend about a third of our lives asleep. The lack of rejuvenating sleep suppresses disease-fighting immune cells and the entire immune system that fights off viral infections and cancer. This helps explain why people who sleep 7 to 8 hours a night tend to outlive those who are chronically sleep deprived. Adults who have no difficulty falling and staying asleep tend to live longer.
This report is not a diagnosis. We hope this information can guide you toward improving your life.
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