Many people with narcolepsy also have insomnia for extended periods of time. The excessive daytime sleepiness and cataplexy often become severe enough to cause serious problems in a persons social, personal, and professional life. Normally, when an individual is awake, brain waves show a regular rhythm. When a person first falls asleep, the brain waves become slower and less regular, which is called non-rapid eye movement (NREM) sleep. After about an hour and a half of NREM sleep, the brain waves begin to show a more active pattern again, called REM sleep (rapid eye movement sleep), when most remembered dreaming occurs. Associated with the EEG-observed waves during REM sleep, muscle atonia is present called REM atonia.In narcolepsy, the order and length of NREM and REM sleep periods are disturbed, with REM sleep occurring at sleep onset instead of after a period of NREM sleep. Also, some aspects of REM sleep that normally occur only during sleep, like lack of muscular control, sleep paralysis, and vivid dreams, occur at other times in people with narcolepsy. For example, the lack of muscular control can occur during wakefulness in a cataplexy episode; it is said that there is an intrusion of REM atonia during wakefulness. Sleep paralysis and vivid dreams can occur while falling asleep or waking up.
It also acts as a neurotransmitter to enable nerve cells to communicate.In up to 10% of cases there is a family history of the disorder. Family history is more common in narcolepsy with cataplexy. There is a strong link with certain genetic variants, which may make T-cells susceptible to react to the orexin-releasing neurons (autoimmunity) after being stimulated by infection with H1N1 influenza. In addition to genetic factors, low levels of orexin peptides have been correlated with a history of infection, diet, contact with toxins such as pesticides, and brain injuries due to head trauma, brain tumors or strokes. Genetics
The primary genetic factor that has been strongly implicated in the development of narcolepsy involves an area of chromosome 6 known as the human leukocyte antigen (HLA) complex. Specific variations in HLA genes are strongly correlated with the presence of narcolepsy (HLA DQB1*06:02, frequently in combination with HLA DRB1*15:01); however, these variations are not required for the condition to occur and sometimes occur in individuals without narcolepsy. These genetic variations in the HLA complex are thought to increase the risk of an auto-immune response to orexin-releasing neurons in the lateral hypothalamus.The allele HLA-DQB1*06:02 of the human gene HLA-DQB1 was reported in more than 90% of people with narcolepsy, and alleles of other HLA genes such as HLA-DQA1*01:02 have been linked. A 2009 study found a strong association with polymorphisms in the TRAC gene locus (dbSNP IDs rs1154155, rs12587781, and rs1263646).