Bed partners may report very harsh and loud interrupted snoring. Central sleep apnea is much less common and occurs when the brain fails to signal the muscles to breathe. Oxygen levels drop abruptly and usually the sleeper wakes with a start. Often people with central sleep apnea recall waking up. They generally experience less sleepiness during the day than people with obstructive sleep apnea.
Mixed apnea is the term used when the two apneas occur together.
Four basic diagnostic criteria exist for narcolepsy. All people with narcolepsy experience excessive sleepiness during the day with episodes of falling asleep rapidly and inappropriately while performing tasks. For example, in the middle of laughter or sudden anger, the patients knees may buckle or the head will suddenly fall forward and the jaw become slack. Muscle reflexes are completely absent during a cataleptic attack, and, in severe cases, a person may fall and remain paralyzed for as long as several minutes. The same percentage of people with narcolepsy have atonia, a sense of paralysis that occurs between wakefulness and sleep when the person is conscious but cannot speak or move.