Sleep Stages
- Stage 1 could be termed as dozing. It is a transitional period of very light sleep in which an individual is easily awakened. It is during this stage that sleepers may experience a sensation of falling and jerk suddenly into wakefulness. This is called a hypnic jerk.
- Stage 2 is often considered the official onset of consolidated sleep. The majority of sleep is spent in stage 2.
- Stages 3 and 4 are characterized by very deep sleep. Sleepers are very difficult to arouse during this time and often feel groggy and disoriented for several minutes. REM (Rapid Eye Movement) sleep is often referred to as dream sleep. During this time, the brain blocks signals to the muscles to remain immobile so dreams will not be acted out.
Why Do We Sleep?
There are two basic theories on why we need to sleep.
- Restorative: Sleep enables the body and mind to rejuvenate, reenergize and restore. As a person sleeps, it is thought that the brain performs vital housekeeping tasks such as organizing long-term memory, integrating new information and repairing and renewing tissue, nerve cells and other biochemicals.
- Adaptation: Sleep may have evolved as a protective adaptation - finding food in the daytime and hiding at night is easier.
Why Is Sleep Important?
Sleep is a necessary and vital function. Studies have shown that without enough sleep, a person's ability to perform even simple tasks declines dramatically. A sleep-deprived individual may experience impaired performance, irritability, lack of concentration and daytime drowsiness. Persistent sleep deprivation can cause significant mood swings, erratic behavior, hallucinations and in rare cases, death.
It is estimated that nearly 50% of the adult population in the U.S. is sleep deprived. The most common consequence of sleep loss is sleeping behind the wheel. One third of all drivers have fallen asleep at the wheel. The monetary cost is approximately 30 billion dollars annually and the human cost is roughly 100,000 crashes, 71,000 injuries and 1500 fatalities a year.
How Much Sleep Do We Need?
Six to eight hours per day is the average amount a person needs to sleep. Sleep requirements vary from person to person. Some people are naturally short or long sleepers. Determine the amount of sleep you need by keeping track of how long you sleep without using an alarm clock for a week.