title: Risk factors for hospital admission with RSV bronchiolitis in England: a population-based birth cohort study.
abstract: OBJECTIVE
  To examine the timing and duration of RSV bronchiolitis hospital admission among term and preterm infants in England and to identify risk factors for bronchiolitis admission.
  
  
  METHODS
  A population-based birth cohort with follow-up to age 1 year, using the Hospital Episode Statistics database.
  
  
  METHODS
  71 hospitals across England.
  
  
  METHODS
  We identified 296618 individual birth records from 2007/08 and linked to subsequent hospital admission records during the first year of life.
  
  
  RESULTS
  In our cohort there were 7189 hospital admissions with a diagnosis of bronchiolitis, 24.2 admissions per 1000 infants under 1 year (95%CI 23.7-24.8), of which 15% (1050/7189) were born preterm (47.3 bronchiolitis admissions per 1000 preterm infants (95% CI 44.4-50.2)). The peak age group for bronchiolitis admissions was infants aged 1 month and the median was age 120 days (IQR = 61-209 days). The median length of stay was 1 day (IQR = 0-3). The relative risk (RR) of a bronchiolitis admission was higher among infants with known risk factors for severe RSV infection, including those born preterm (RR = 1.9, 95% CI 1.8-2.0) compared with infants born at term. Other conditions also significantly increased risk of bronchiolitis admission, including Down's syndrome (RR = 2.5, 95% CI 1.7-3.7) and cerebral palsy (RR = 2.4, 95% CI 1.5-4.0).
  
  
  CONCLUSIONS
  Most (85%) of the infants who are admitted to hospital with bronchiolitis in England are born at term, with no known predisposing risk factors for severe RSV infection, although risk of admission is higher in known risk groups. The early age of bronchiolitis admissions has important implications for the potential impact and timing of future active and passive immunisations. More research is needed to explain why babies born with Down's syndrome and cerebral palsy are also at higher risk of hospital admission with RSV bronchiolitis.
authors.affiliation: Department of Primary Care and Public Health, Imperial College London, London, United Kingdom.
authors.forename: Joanna
authors.initials: J
authors.lastname: Murray
authors.affiliation: Department of Primary Care and Public Health, Imperial College London, London, United Kingdom.
authors.forename: Alex
authors.initials: A
authors.lastname: Bottle
authors.affiliation: Paediatric Infectious Diseases Unit, St. George's Hospital NHS Trust, London, United Kingdom.
authors.forename: Mike
authors.initials: M
authors.lastname: Sharland
authors.affiliation: Section of Neonatal Medicine, Department of Medicine, Imperial College London, London, United Kingdom.
authors.forename: Neena
authors.initials: N
authors.lastname: Modi
authors.affiliation: Department of Primary Care and Public Health, Imperial College London, London, United Kingdom.
authors.forename: Paul
authors.initials: P
authors.lastname: Aylin
authors.affiliation: Department of Primary Care and Public Health, Imperial College London, London, United Kingdom.
authors.forename: Azeem
authors.initials: A
authors.lastname: Majeed
authors.affiliation: Department of Primary Care and Public Health, Imperial College London, London, United Kingdom.
authors.forename: Sonia
authors.initials: S
authors.lastname: Saxena
mesh_terms: D001990:Bronchiolitis, Viral / Q000628:therapy*; D015331:Cohort Studies; D004739:England / Q000453:epidemiology; D006760:Hospitalization; D006801:Humans; D010343:Patient Admission; D018357:Respiratory Syncytial Virus Infections / Q000628:therapy*; D012307:Risk Factors