title: Exploring the association between severe respiratory syncytial virus infection and asthma: a registry-based twin study.
abstract: BACKGROUND
  Severe respiratory syncytial virus (RSV) infection is associated with asthma but the nature of this association is imperfectly understood.
  
  
  OBJECTIVE
  To examine the nature of the association between severe RSV infection and asthma in a population-based sample of twins.
  
  
  METHODS
  Data on hospitalization due to RSV infection was gathered for all twins born in Denmark between 1994 and 2000 (8,280 pairs) and linked to information on asthma obtained from hospital discharge registries and parent-completed questionnaires. Genetic variance components models and direction of causation models were fitted to the observed data.
  
  
  RESULTS
  RSV hospitalization and asthma were positively associated (r = 0.43), and genetic determinants for the two disorders overlapped completely. Modeling the direction of causation between RSV hospitalization and asthma showed that a model in which asthma "causes" RSV hospitalization fitted the data significantly better (P = 0.39 for deterioration in model fit) than a model in which RSV hospitalization "causes" asthma (P < 0.001 for deterioration in model fit), even when sex, birth weight, and maternal smoking during pregnancy were accounted for.
  
  
  CONCLUSIONS
  RSV infection that is severe enough to warrant hospitalization does not cause asthma but is an indicator of the genetic predisposition to asthma.
authors.affiliation: Department of Respiratory Medicine, Bispebjerg Hospital, Copenhagen NV, Denmark. sft@city.dk
authors.forename: Simon Francis
authors.initials: SF
authors.lastname: Thomsen
authors.forename: Sophie
authors.initials: S
authors.lastname: van der Sluis
authors.forename: Lone G
authors.initials: LG
authors.lastname: Stensballe
authors.forename: Danielle
authors.initials: D
authors.lastname: Posthuma
authors.forename: Axel
authors.initials: A
authors.lastname: Skytthe
authors.forename: Kirsten O
authors.initials: KO
authors.lastname: Kyvik
authors.forename: David L
authors.initials: DL
authors.lastname: Duffy
authors.forename: Vibeke
authors.initials: V
authors.lastname: Backer
authors.forename: Hans
authors.initials: H
authors.lastname: Bisgaard
mesh_terms: D000956:Antigens, Viral / Q000032:analysis*; D001249:Asthma / Q000453:epidemiology / Q000209:etiology*; D002648:Child; D002675:Child, Preschool; D003718:Denmark / Q000453:epidemiology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005500:Follow-Up Studies; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D008297:Male; D008962:Models, Theoretical; D011379:Prognosis; D012042:Registries; D018357:Respiratory Syncytial Virus Infections / Q000150:complications* / Q000453:epidemiology / Q000821:virology; D018113:Respiratory Syncytial Virus, Human / Q000276:immunology*; D012189:Retrospective Studies; D012307:Risk Factors; D014427:Twins / Q000235:genetics*
chemical_list: D000956:Antigens, Viral