title: Narcolepsy and hypersomnia in Norwegian children and young adults following the influenza A(H1N1) 2009 pandemic.
abstract: Associations between influenza infection and sleep disorders are poorly studied. We investigated if pandemic influenza infection or vaccination with Pandemrix in 2009/2010 was associated with narcolepsy or hypersomnia in children and young adults.
  
  
  
  We followed the Norwegian population under age 30 from January 2008 through December 2012 by linking national health registry data. Narcolepsy diagnoses were validated using hospital records. Risks of narcolepsy or hypersomnia were estimated as adjusted hazard ratios (HRs) in Cox regression models with influenza infection and vaccination as time-dependent exposures.
  
  
  
  Among the 1,638,526 persons under age 30 in Norway in 2009, 3.6% received a physician diagnosis of influenza during the pandemic, while 41.9% were vaccinated against pandemic influenza. Between October 1st 2009 and December 31st 2012, 72 persons had onset of narcolepsy and 305 were diagnosed with hypersomnia. The risk of a sleep disorder was associated with infection during the first six months, adjusted HR 3.31 with 95% confidence interval [CI], 1.01-10.79 for narcolepsy and adjusted HR 3.13 (95% CI, 1.12-8.76) for hypersomnia. The risk of narcolepsy was strongly associated with vaccination during the first six months adjusted HR 17.21 (95% CI, 6.28-47.14), while the adjusted HR for hypersomnia was 1.54 (95% CI, 0.81-2.93).
  
  
  
  The study confirms an increased HR of narcolepsy following pandemic vaccination. Slightly increased HRs of narcolepsy and hypersomnia are also seen after influenza infection. However, the role of infection should be viewed with caution due to underreporting of influenza.
authors.affiliation: Norwegian Institute of Public Health, Norway. Electronic address: lill.trogstad@fhi.no.
authors.forename: Lill
authors.initials: L
authors.lastname: Trogstad
authors.affiliation: Norwegian Institute of Public Health, Norway. Electronic address: inger.johanne.bakken@fhi.no.
authors.forename: Inger Johanne
authors.initials: IJ
authors.lastname: Bakken
authors.affiliation: Norwegian Institute of Public Health, Norway. Electronic address: nina.gunnes@fhi.no.
authors.forename: Nina
authors.initials: N
authors.lastname: Gunnes
authors.affiliation: Norwegian Institute of Public Health, Norway. Electronic address: sara.ghaderi@fhi.no.
authors.forename: Sara
authors.initials: S
authors.lastname: Ghaderi
authors.affiliation: Norwegian Institute of Public Health, Norway; University of Bergen, Bergen, Norway. Electronic address: camilla.stoltenberg@fhi.no.
authors.forename: Camilla
authors.initials: C
authors.lastname: Stoltenberg
authors.affiliation: Norwegian Institute of Public Health, Norway; University of Oslo, Oslo, Norway. Electronic address: per.magnus@fhi.no.
authors.forename: Per
authors.initials: P
authors.lastname: Magnus
authors.affiliation: Norwegian Institute of Public Health, Norway. Electronic address: siri.haberg@fhi.no.
authors.forename: Siri E
authors.initials: SE
authors.lastname: Håberg
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D006970:Disorders of Excessive Somnolence / Q000453:epidemiology*; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000009:adverse effects*; D007251:Influenza, Human / Q000150:complications* / Q000453:epidemiology / Q000821:virology*; D008297:Male; D009664:Norway / Q000453:epidemiology; D058873:Pandemics; D018570:Risk Assessment; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines; C556153:pandemrix
keywords: Immunisation registry; Influenza A(H1N1)pdm09; Narcolepsy, hypersomnia; Pandemic vaccination; Pandemrix