title: Narcolepsy in African Americans.
abstract: OBJECTIVE
  Although narcolepsy affects 0.02-0.05% of individuals in various ethnic groups, clinical presentation in different ethnicities has never been fully characterized. Our goal was to study phenotypic expression across ethnicities in the United States.
  
  
  METHODS
  Cases of narcolepsy from 1992 to 2013 were identified from searches of the Stanford Center for Narcolepsy Research database. International Classification of Sleep Disorders, Third Edition diagnosis criteria for type 1 and type 2 narcolepsy were used for inclusion, but subjects were separated as with and without cataplexy for the purpose of data presentation. Information extracted included demographics, ethnicity and clinical data, HLA-DQB1*06:02, polysomnography (PSG), multiple sleep latency test (MSLT) data, and cerebrospinal fluid (CSF) hypocretin-1 level.
  
  
  METHODS
  182 African-Americans, 839 Caucasians, 35 Asians, and 41 Latinos with narcolepsy.
  
  
  RESULTS
  Sex ratio, PSG, and MSLT findings did not differ across ethnicities. Epworth Sleepiness Scale (ESS) score was higher and age of onset of sleepiness earlier in African Americans compared with other ethnicities. HLA-DQB1*06:02 positivity was higher in African Americans (91.0%) versus others (76.6% in Caucasians, 80.0% in Asians, and 65.0% in Latinos). CSF hypocretin-1 level, obtained in 222 patients, was more frequently low (≤ 110 pg/ml) in African Americans (93.9%) versus Caucasians (61.5%), Asians (85.7%) and Latinos (75.0%). In subjects with low CSF hypocretin-1, African Americans (28.3%) were 4.5 fold more likely to be without cataplexy when compared with Caucasians (8.1%).
  
  
  CONCLUSIONS
  Narcolepsy in African Americans is characterized by earlier symptom onset, higher Epworth Sleepiness Scale score, higher HLA-DQB1*06:02 positivity, and low cerebrospinal fluid hypocretin-1 level in the absence of cataplexy. In African Americans, more subjects without cataplexy have type 1 narcolepsy.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Stanford University, School of Medicine, Stanford, CA.|Sierra Pacific Mental Illness Research Education and Clinical Centers, VA Palo Alto Health Care System, Palo Alto, CA.
authors.forename: Makoto
authors.initials: M
authors.lastname: Kawai
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Stanford University, School of Medicine, Stanford, CA.|Sierra Pacific Mental Illness Research Education and Clinical Centers, VA Palo Alto Health Care System, Palo Alto, CA.
authors.forename: Ruth
authors.initials: R
authors.lastname: O'Hara
authors.affiliation: Center for Sleep Sciences and Medicine, Department of Psychiatry and Behavioral Sciences, Stanford University, School of Medicine, Palo Alto, CA.
authors.forename: Mali
authors.initials: M
authors.lastname: Einen
authors.affiliation: Center for Sleep Sciences and Medicine, Department of Psychiatry and Behavioral Sciences, Stanford University, School of Medicine, Palo Alto, CA.
authors.forename: Ling
authors.initials: L
authors.lastname: Lin
authors.affiliation: Center for Sleep Sciences and Medicine, Department of Psychiatry and Behavioral Sciences, Stanford University, School of Medicine, Palo Alto, CA.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Mignot
mesh_terms: D000328:Adult; D001741:Black or African American / Q000235:genetics / Q000706:statistics & numerical data*; D002385:Cataplexy / Q000453:epidemiology; D005260:Female; D059866:HLA-DQ beta-Chains / Q000235:genetics; D006630:Hispanic or Latino / Q000235:genetics / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D009290:Narcolepsy / Q000453:epidemiology*; D000068797:Orexins / Q000134:cerebrospinal fluid; D017286:Polysomnography; D012744:Sex Ratio; D012894:Sleep Stages; D014481:United States / Q000453:epidemiology; D044465:White People / Q000235:genetics / Q000706:statistics & numerical data
chemical_list: D059866:HLA-DQ beta-Chains; C069051:HLA-DQB1 antigen; D000068797:Orexins
keywords: African American; Asian; Caucasian; HLA DQB1*06:02; Latino; cataplexy; hypocretin-1; narcolepsy