title: Chronic diseases, chromosomal abnormalities, and congenital malformations as risk factors for respiratory syncytial virus hospitalization: a population-based cohort study.
abstract: BACKGROUND
  Little is known about how chronic conditions other than prematurity, heart disease, and Down syndrome affect the risk and severity of hospitalization for respiratory syncytial virus (RSV). We assess the risk and severity of RSV hospitalization in children with chronic conditions in this register-based, population-based cohort study.
  
  
  METHODS
  Data on RSV tests, maternal smoking, siblings, single parenthood, mode of delivery, gestational age at birth, major surgery, asthma diagnosis, chronic conditions, and hospitalization and discharge dates were obtained from the Danish RSV database, the National Patient and Birth Registries, and the Civil Registration System.
  
  
  METHODS
  Cox regression models were used to estimate incidence rate ratios (IRRs) for RSV hospitalization between groups stratified by sex and date of birth. Duration of RSV hospitalization was analyzed in a linear regression and reported as geometric mean ratios.
  
  
  RESULTS
  A total of 391 983 children aged 0-23 months were included in the analysis. A total of 10,616 (2.7%) had a diagnosis for chronic disease. IRRs (95% confidence intervals) for RSV hospitalization in children with any congenital or acquired chronic condition were 2.18 (2.01-2.36) and 2.25 (1.94-2.61), respectively. Several new risk factors for RSV hospitalization, including malformations, interstitial lung disease, neuromuscular disease, liver disease, chromosomal abnormalities, congenital immunodeficiencies, and inborn errors of metabolism, were identified. Duration of RSV hospitalization was increased in many chronic conditions.
  
  
  CONCLUSIONS
  Chronic disease per se is an important risk factor for RSV hospitalization.
authors.affiliation: Paediatric Clinic 2, Statens Serum Institut, Copenhagen, Denmark. kimk@dadlnet.dk
authors.forename: Kim
authors.initials: K
authors.lastname: Kristensen
authors.forename: Thomas
authors.initials: T
authors.lastname: Hjuler
authors.forename: Henrik
authors.initials: H
authors.lastname: Ravn
authors.forename: Eric A F
authors.initials: EA
authors.lastname: Simões
authors.forename: Lone G
authors.initials: LG
authors.lastname: Stensballe
mesh_terms: D002869:Chromosome Aberrations; D002908:Chronic Disease; D015331:Cohort Studies; D003718:Denmark; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007154:Immune System Diseases / Q000150:complications / Q000151:congenital; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007902:Length of Stay; D008107:Liver Diseases / Q000150:complications; D017563:Lung Diseases, Interstitial / Q000150:complications; D008661:Metabolism, Inborn Errors / Q000150:complications; D009468:Neuromuscular Diseases / Q000150:complications; D016016:Proportional Hazards Models; D012042:Registries; D018357:Respiratory Syncytial Virus Infections / Q000150:complications* / Q000821:virology; D012136:Respiratory Syncytial Viruses; D012307:Risk Factors; D012720:Severity of Illness Index