An important distinction between the two, however, is that those with hypersomnia tend to awaken from these naps unrefreshed and disoriented, while narcoleptics typically will wake up feeling rested, if only for a few hours.   


Idiopathic hypersomnia rarely causes cataplexy, sleep paralysis or hallucinations and most people with the disorder have a relatively normal REM sleep cycle. Most importantly people with hypersomnia do not have a decreased level of hypocretin in their cerebrospinal fluid. 


An interesting, although rare, variation of hypersomnia is a condition known as Kliene-Levin syndrome, or “KLS.”  Most common in teenaged males, it is characterized by excessive sleeping, sometimes up to 18 hours per day, and a severely altered mental state with irritability, impaired cognition, anxiety, and confusion during periods of wakefulness.  About 75% of patients with KLS also experience an extreme increase in appetite, sometimes devouring enormous quantities of food at a single sitting, and approximately 50% engage in atypical sexual behavior, including promiscuity, inappropriately aggressive sexual advances and even sexual assault. Almost all sufferers will have no memory of these events after they occur.  


Like idiopathic hypersomnia, KLS is a chronic disorder and many patients develop depression or other mood disorders due to the bizarre effects of the disease. Excessive eating often causes weight gain to the point of obesity, and episodes of extreme sleepiness from which the person cannot be aroused interfere with patient’s ability to work, attend school or engage in normal, age appropriate activities. When KLS is associated with hypersexual behavior, patients may suffer severe repercussions, including loss of social contacts, social stigmatization and –in cases where the sexual behavior is aggressive,-even arrest and incarceration.  Fortunately, KLS is usually a self-limiting disease, lasting from 18 months to about four years. 


Another common cause of excessive daytime sleepiness is sleep apnea, also called “obstructive sleep apnea” or “OSA.” OSA is much more common than either narcolepsy or hypersomnia, affecting an estimated 18 million Americans, both male and female. 


OSA is caused by obstruction or compression of the normal air passages during sleep, usually by the soft palate, tonsils or, occasionally, the tongue. This results in shallow respiration, snoring and-when obstruction is severe- frequent pauses in breathing, sometimes up to 100 times every hour. These pauses are known as apnea or apneic episodes. They cause sleep disruption, frequent awakening and generally poor sleep quality, which results in daytime sleepiness. 


While OSA can occur in healthy people of any age, it is most commonly associated with a number of other physical and/or physiologic conditions, especially-





Another form of sleep apnea that is less common than OSA is “central apnea.” Central apnea is characterized by depression of the normal drive to breathe, which is a function of the central nervous system. Central apnea most often occurs as the result of medications that act on the central nervous system, particularly narcotics or opiates, barbiturates, benzodiazepines and alcohol; it can occur in persons who take these medicines even in the recommended dosage, especially if they are used in combination with other drugs. 