In the Stanford study, which was funding by the National Institute of Health's Division of Neurological Disorders and Strokes (NINDS) researchers set out to find what immune system influences contribute to narcolepsy.
Understanding Narcolepsy
Narcolepsy is a disorder characterized by daytime drowsiness, brief episodes of daytime sleep that occur without warning, dreaming during periods of wakefulness, irregular sleep patterns at night, sleep paralysis, hallucinations, and cataplexy, which is a sudden loss of muscle tone and strength. Narcolepsy is also associated with food cravings, binge eating, and other metabolic changes that lead to weight gain. Patients with narcolepsy have also been found to have a higher incidence of bulimia nervosa.
Although blood prolactin levels have long been found to be twice as high in patients with narcolepsy, previous studies have shown that other physiological parameters such as blood sugar, thyroid status, and cortisol are not noticeably different.
Who is Affected?
Narcolepsy is seen in about 1 of every 2000 people. As with other autoimmune diseases, narcolepsy is associated with variable degrees of severity.
Cause of Narcolepsy
Narcolepsy occurs when there is a deficiency of hypocretin, a hormone that promotes wakefulness. The Stanford team, lead by Dr. Emmanuelle Mignot theorizes that the immune system destroys hypocretin-producing cells, causing this deficiency. Their findings were published in the May3, 2009 online issue of Nature Genetics. An association between certain HLA genes and narcolepsy was the first clue that the immune system played a key role in narcolepsy.
Studies show that narcolepsy patients who also have cataplexy have low cerebrospinal levels of hypercetin-1. These patients show more intensive muscular involvement during cataplectic attacks than patients with normal levels of hypercetin in their cerebrospinal fluid.
Mignot has found that variations of a gene regulating T cells is the primary culprit. Mignot and his team are still studying the ways in which the two gene mutations in narcolepsy interact to destroy hypercetin. This could lead to an earlier diagnosis of a predisposition to narcolepsy, and it could lead to better treatment interventions.
Environmental Exposures
Will Longstreth Jr., MD, MPH, and colleagues at the University of Washington identified and assessed studies previously conducted by other researchers on the epidemiology of narcolepsy. They’ve determined that changes in body mass index are more likely to be caused by narcolepsy that to be risk factors. The researchers, however, suspect that as yet unidentified environmental triggers that genetically predisposed individuals are exposed to during their first two decades of life add risk for narcolepsy.
Source:
Kevin McKeever, Research IDs Narcolepsy as Autoimmune Disease, 2009 Health Day News, May 4, 2009.
Narcolepsy May Be Caused By Environmental Exposure, Science Daily News, January 2, 2007.
 |
