title: Narcolepsy onset is seasonal and increased following the 2009 H1N1 pandemic in China.
abstract: OBJECTIVE
  Narcolepsy is caused by the loss of hypocretin/orexin neurons in the hypothalamus, which is likely the result of an autoimmune process. Recently, concern has been raised over reports of narcolepsy in northern Europe following H1N1 vaccination.
  
  
  METHODS
  The study is a retrospective analysis of narcolepsy onset in subjects diagnosed in Beijing, China (1998-2010). Self-reported month and year of onset were collected from 629 patients (86% children). Graphical presentation, autocorrelations, chi-square, and Fourier analysis were used to assess monthly variation in onset. Finally, 182 patients having developed narcolepsy after October 2009 were asked for vaccination history.
  
  
  RESULTS
  The occurrence of narcolepsy onset was seasonal, significantly influenced by month and calendar year. Onset was least frequent in November and most frequent in April, with a 6.7-fold increase from trough to peak. Studying year-to-year variation, we found a 3-fold increase in narcolepsy onset following the 2009 H1N1 winter influenza pandemic. The increase is unlikely to be explained by increased vaccination, as only 8 of 142 (5.6%) patients recalled receiving an H1N1 vaccination. Cross-correlation indicated a significant 5- to 7-month delay between the seasonal peak in influenza/cold or H1N1 infections and peak in narcolepsy onset occurrences.
  
  
  CONCLUSIONS
  In China, narcolepsy onset is highly correlated with seasonal and annual patterns of upper airway infections, including H1N1 influenza. In 2010, the peak seasonal onset of narcolepsy was phase delayed by 6 months relative to winter H1N1 infections, and the correlation was independent of H1N1 vaccination in the majority of the sample.
authors.affiliation: Department of Pulmonary Medicine, Beijing University People's Hospital, Beijing, China. hanfang1@hotmail.com
authors.forename: Fang
authors.initials: F
authors.lastname: Han
authors.forename: Ling
authors.initials: L
authors.lastname: Lin
authors.forename: Simon C
authors.initials: SC
authors.lastname: Warby
authors.forename: Juliette
authors.initials: J
authors.lastname: Faraco
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Song X
authors.initials: SX
authors.lastname: Dong
authors.forename: Pei
authors.initials: P
authors.lastname: An
authors.forename: Long
authors.initials: L
authors.lastname: Zhao
authors.forename: Ling H
authors.initials: LH
authors.lastname: Wang
authors.forename: Qian Y
authors.initials: QY
authors.lastname: Li
authors.forename: Han
authors.initials: H
authors.lastname: Yan
authors.forename: Zhan C
authors.initials: ZC
authors.lastname: Gao
authors.forename: Yuan
authors.initials: Y
authors.lastname: Yuan
authors.forename: Kingman P
authors.initials: KP
authors.lastname: Strohl
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Mignot
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002681:China / Q000453:epidemiology; D003139:Common Cold / Q000453:epidemiology; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D009290:Narcolepsy / Q000453:epidemiology*; D058873:Pandemics; D017286:Polysomnography; D012189:Retrospective Studies; D012621:Seasons; D014611:Vaccination / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines