Investigation of a protein in the brain called hypocretin that helps regulate sleep and wakefulness has yielded a new discovery that changes how medical researchers understand the chronic sleep disorder narcolepsy. Narcoleptic people are subject to sudden attacks of sleeping during the day that are not connected to the type of activities they are engaged in at the time.
The most prominent symptom of narcolepsy is suddenly nodding off, sleeping anywhere from a few minutes to half an hour before waking up. This daytime sleepiness makes concentrating on tasks difficult, as well as disrupting daily functioning. Another symptom is sudden loss of muscle tone, where the muscles weaken for a few minutes without warning. This can look like a seizure, but it isn’t really. Unlike the sleepiness, which is completely unpredictable, the weakness—called "cataplexy"—is associated with strong, usually positive emotions. Cataplexy is not as common a symptom as the sleep attacks that give the condition its name, and may not be a daily occurrence as the sleep often is.
While the exact cause of narcolepsy has long been difficult to pin down, researchers have now confirmed it to be an autoimmune disease, in which the immune system treats healthy tissue as an infection. In particular, narcolepsy is caused, at least in some instances, by an immune response targeting the parts of the brain that produce hypocretin. Hypocretin is the neurotransmitter produced when the body has gotten enough sleep and needs to be awake in the daytime. The protein is responsible for wakefulness, and so a hypocretin deficit will cause difficulties staying awake.
Dealing with narcolepsy means avoiding alcohol and nicotine and getting regular, moderate exercise. Maintaining a regular sleep schedule can help keep hypocretin levels up even with production damaged, and taking planned naps during the day can help ward off unplanned and unintended sleep attacks. Stimulants are often prescribed to help patients stay awake, and some types of anti-depressant are also effective against narcolepsy.