title: Season and region of birth as risk factors for coeliac disease a key to the aetiology?
abstract: BACKGROUND
  Coeliac disease (CD) incidence has increased in recent decades, characterised by variations according to sex, age at diagnosis, year of birth, month of birth and region of birth. Genetic susceptibility and exposure to gluten are the necessary factors in CD aetiology, although several environmental factors are considered.
  
  
  METHODS
  A nationwide prospective cohort longitudinal study was conducted consisting of 1 912 204 children aged 0-14.9 years born in Sweden from 1991 to 2009. A total of 6569 children were diagnosed with biopsy-verified CD from 47 paediatric departments. Using Cox regression, we examined the association between CD diagnosis and season of birth, region of birth and year of birth.
  
  
  RESULTS
  Overall, CD risk was higher for children born during spring, summer and autumn as compared with children born during winter: adjusted HR for spring 1.08 (95% CI 1.01 to 1.16), summer 1.10 (95% CI 1.03 to 1.18) and autumn 1.10 (95% CI 1.02 to 1.18). Increased CD risk was highest if born in the south, followed by central Sweden when compared with children born in northern Sweden. Children diagnosed at <2 years had an increased CD risk if born in spring while those diagnosed at 2-14.9 years the risk was increased for summer and autumn births. The birth cohort of 1991-1996 had increased CD risk if born during spring, for the 1997-2002 birth cohort the risk increased for summer and autumn births, while for the birth cohort of 2003-2009 the risk was increased if born during autumn.
  
  
  CONCLUSIONS
  Season of birth and region of birth are independently and jointly associated with increased risk of developing CD during the first 15 years of life. Seasonal variation in infectious load is the likely explanation.
authors.affiliation: Department of Public Health and Clinical Medicine, Epidemiology and Global Health, Umeå University, Umeå, Sweden.
authors.forename: Fredinah
authors.initials: F
authors.lastname: Namatovu
authors.affiliation: Department of Public Health and Clinical Medicine, Epidemiology and Global Health, Umeå University, Umeå, Sweden.
authors.forename: Marie
authors.initials: M
authors.lastname: Lindkvist
authors.affiliation: Department of Food and Nutrition, Umeå University, Umeå, Sweden.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Olsson
authors.affiliation: Department of Public Health and Clinical Medicine, Epidemiology and Global Health, Umeå University, Umeå, Sweden.
authors.forename: Anneli
authors.initials: A
authors.lastname: Ivarsson
authors.affiliation: Department of Public Health and Clinical Medicine, Epidemiology and Global Health, Umeå University, Umeå, Sweden.|Department of Clinical Sciences, Pediatrics, Umeå University, Umeå, Sweden.
authors.forename: Olof
authors.initials: O
authors.lastname: Sandström
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D002446:Celiac Disease / Q000453:epidemiology* / Q000209:etiology; D002648:Child; D002675:Child, Preschool; D004812:Epidemiologic Methods; D020022:Genetic Predisposition to Disease / Q000453:epidemiology / Q000235:genetics; D005983:Glutens / Q000009:adverse effects; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D012111:Residence Characteristics / Q000706:statistics & numerical data; D012621:Seasons; D017678:Sex Distribution; D013548:Sweden / Q000453:epidemiology
chemical_list: D005983:Glutens
keywords: Epidemiology; Gastroenterology; General Paediatrics