Causes of Narcolepsy
Narcolepsy is a syndrome of unknown cause; therefore, it is helpful to look at related problems. Narcoleptic dysfunction may be associated with genetic links, rapid eye movement (REM) sleep disorder, and blood pressure issues.
Although poorly defined, there is some hereditary component to the occurrence of narcolepsy. People with narcolepsy have a slightly increased incidence of it in the family. In fact, narcolepsy fits the paradigm established by most sleep disorders, in which there exists a family history of a specifically nonhereditary disorder.
However, there is a genetic linkage between narcolepsy and a certain human leukocyte antigen (HLA) type, HLA DQB1 0602. Approximately 90 to 100 percent of patients with narcolepsy have this HLA type, as opposed to less than 50 percent of nonnarcoleptic patients.
Despite the fact that these findings are currently inconclusive, they suggest that immune system studies are the future of genetic narcolepsy investigation. It may be that all sleep disorder patients share a genetic predisposition to their symptoms.
Physiologically, there are several interrelated functions that seem to precede and accompany the various symptoms of narcolepsy. Narcolepsy patients have shown REM sleep control dysfunction in some studies. Specifically, immediate REM sleep characterizes narcoleptic sleep attacks.
In patients with normal sleep-wake patterns, REM sleep usually occurs 90 minutes after sleep onset. In some studies, 50 percent of patients with narcolepsy experienced REM sleep within the first 10 minutes of sleep. The result is a disruption of the natural sleep cycle, replete with myoclonic movements and less time spent in deep sleep. The cause may be a general change in biorhythm associated with narcolepsy.
There has also been some speculation about the function of blood pressure regulation in narcolepsy. Blood pressure fluctuation has been linked to the atony (loss of muscle tone) patients experience while in a cataplexic state. Furthermore, a similar loss of muscle tone is characteristic of REM sleep.