Narcolepsy onset is seasonal and increased following the 2009 H1N1 pandemic in China

Ann Neurol. 2011 Sep;70(3):410-7. doi: 10.1002/ana.22587. Epub 2011 Aug 22.

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.

Interpretation: 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Child
  • China / epidemiology
  • Common Cold / epidemiology
  • Data Interpretation, Statistical
  • Female
  • Humans
  • Influenza A Virus, H1N1 Subtype*
  • Influenza Vaccines
  • Influenza, Human / epidemiology*
  • Male
  • Middle Aged
  • Narcolepsy / epidemiology*
  • Pandemics
  • Polysomnography
  • Retrospective Studies
  • Seasons*
  • Vaccination / statistics & numerical data
  • Young Adult

Substances

  • Influenza Vaccines