title: Risk Factors of Early Otitis Media in the Danish National Birth Cohort.
abstract: OBJECTIVE
  To assess risk factors of otitis media (OM) in six-months-old children.
  
  
  METHODS
  The sample consisted of 69,105 mothers and their children from the Danish National Birth Cohort. The women were interviewed twice during pregnancy and again 6 months after birth. The outcome "one or more" maternal reported episodes of OM at age six months. In total 37 factors were assessed, covering prenatal, maternal, perinatal and postnatal factors.
  
  
  RESULTS
  At age six months 5.3% (95% CI 5.1-5.5) of the children had experienced one or more episodes of OM. From the regression analysis, 11 variables were associated with a risk of OM. When a Bonferroni correction was introduced, gender, prematurity, parity, maternal age, maternal self-estimated health, taking penicillin during pregnancy, and terminating breastfeeding before age six months, was associated with a risk of early OM. The adjusted ORs of OM for boys versus girls was 1.30 (95% CI 1.18-1.44). The OR having one sibling versus no siblings was 3.0 (95% CI 2.64-3.41). If the woman had been taking penicillin during pregnancy, the OR was 1.35 (95% CI 1.15-1.58). Children born before 38th gestational week had an increased OR for early OM of 1.49 (95% CI 1.21-1.82). Children of young women had an increased OR of early OM compared to children of older women. Additionally, children of women who rated their own health low compared to those rating their health as high, had an increased OR of 1.38 (95% CI 1.10-1.74). Finally, children being breastfeed less than 6 months, had an increased OR of 1.42 (95% CI 1.28-1.58) compared to children being breastfeed beyond 6 months.
  
  
  CONCLUSIONS
  These findings indicate that prenatal factors are of less importance regarding early OM before the age of six months. Postnatal risk factors seem to pose the main risk of early OM.
authors.affiliation: Department of Otorhinolaryngology and Maxillofacial Surgery, Zealand University Hospital, Køge, Denmark.
authors.forename: Asbjørn
authors.identifier: http://orcid.org/0000-0002-6645-1926
authors.initials: A
authors.lastname: Kørvel-Hanquist
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark.|Department of Infectious Disease Epidemiology, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Anders
authors.initials: A
authors.lastname: Koch
authors.affiliation: Department of Psychology, University of Copenhagen, Copenhagen, Denmark.|Center for Collaborative Health, Aarhus University, Aarhus, Denmark.
authors.forename: Janni
authors.initials: J
authors.lastname: Niclasen
authors.affiliation: Department of Psychology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Dammeye
authors.affiliation: Research Unit for General Practice Institute of Public Health, University of Southern Denmark, Odense, Denmark.
authors.forename: Jørgen
authors.initials: J
authors.lastname: Lous
authors.affiliation: Department of Epidemiology Research, Centre for Fetal Programming, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Sjurdur Frodi
authors.initials: SF
authors.lastname: Olsen
authors.affiliation: Department of Otorhinolaryngology and Maxillofacial Surgery, Zealand University Hospital, Køge, Denmark.
authors.forename: Preben
authors.initials: P
authors.lastname: Homøe
mesh_terms: D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005500:Follow-Up Studies; D006801:Humans; D016017:Odds Ratio; D010033:Otitis Media / Q000453:epidemiology*; D036801:Parturition; D015995:Prevalence; D012307:Risk Factors