Search Sleep disorders are disturbances in falling asleep, staying asleep, or duration of sleep or abnormal sleep behaviors such as night terrors or sleepwalking. Sleep is necessary for survival and good health, but why sleep is needed or exactly how it benefits people is not fully understood. Most people sleep at night, but many must sleep during the day to accommodate work schedules. This situation often leads to sleep disorders.
Most sleep disorders are common.
How long a person sleeps and how rested a person feels on waking can be influenced by many factors, including excitement or emotional distress. In stage 4, the muscles are relaxed, the blood pressure is at its lowest, and the heart and breathing rates are at their slowest. During REM sleep, electrical activity in the brain is unusually high, somewhat resembling that of wakefulness. Most dreaming occurs during REM and stage 3 sleep, while most talking during sleep, night terrors, and sleepwalking occur during stages 3 and 4. Insomnia Insomnia is difficulty in falling asleep or staying asleep or a disturbance in sleep that makes people feel as if they've had insufficient sleep when they awaken.