title: Increased risk of hospital admission for influenza in patients with celiac disease: a nationwide cohort study in Sweden.
abstract: OBJECTIVE
  Although earlier studies suggest an increased risk of infectious disease in celiac disease (CD), data on the risk of influenza in patients with CD are limited. We examined the risk of hospital admission for influenza in CD patients, but for comparative reasons also in individuals with small-intestinal inflammation or normal mucosa but positive CD serology.
  
  
  METHODS
  In 2006-2008, we collected duodenal/jejunal biopsy data on CD (Marsh 3: villous atrophy, VA; n=29,008 unique individuals) and inflammation (Marsh 1-2; n=13,200) from all 28 pathology departments in Sweden. A third regional cohort consisted of 3,709 individuals with positive CD serology but normal mucosa (Marsh 0). The biopsies were performed between 1969 and 2008. Through linkage with the Swedish Hospital Discharge Register, we estimated the risk of hospital admission for influenza compared with that of 224,114 age- and sex-matched controls from the general population.
  
  
  RESULTS
  Individuals with CD were at increased risk of hospital admission for influenza (hazard ratio (HR)=2.1; 95% confidence interval (CI)=1.6-2.7; n=81). The absolute risk of influenza was 30/100,000 person-years (excess risk: 16/100,000 person-years). Furthermore, children with CD were at increased risk of influenza (HR=2.5; 95% CI=1.3-4.8). Whereas individuals with inflammation without VA were also at increased risk of influenza (HR=1.9; 95% CI=1.4-2.5), individuals with normal mucosa but positive CD serology were not (HR=1.2; 95% CI=0.5-3.0).
  
  
  CONCLUSIONS
  This study found an increased risk of hospital admission for influenza in patients with CD.
authors.affiliation: Astrid Lindgren Children's Hospital, Karolinska University Hospital, Solna, Sweden. karlmarild@gmail.com
authors.forename: Karl
authors.initials: K
authors.lastname: Mårild
authors.forename: Hans
authors.initials: H
authors.lastname: Fredlund
authors.forename: Jonas F
authors.initials: JF
authors.lastname: Ludvigsson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002446:Celiac Disease / Q000150:complications* / Q000453:epidemiology* / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D007251:Influenza, Human / Q000150:complications* / Q000453:epidemiology* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D012042:Registries; D012306:Risk; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology