Atopic disposition, wheezing, and subsequent respiratory syncytial virus hospitalization in Danish children younger than 18 months: A nested case-control study

OBJECTIVES. This study examined whether atopic disposition, wheezing, and atopic disorders increased the risk of hospitalizations because of respiratory syncytial virus in children between birth and 18 months of age. PATIENTS AND METHODS. Relative risks for respiratory syncytial virus hospitalization were studied in a nested 1:5 case-control design using exposure information obtained from interviews with mothers of 2564 case and 12 816 control children who had been followed prospectively from birth and until 18 months of age as participants in the Danish National Birth Cohort. Information on the children's ages at respiratory syncytial virus hospitalization, presentation of infrequent wheezing, recurrent wheezing, and atopic dermatitis were used to study these associations chronologically. RESULTS. The adjusted relative risk of respiratory syncytial virus hospitalization in the offspring was 1.11 for maternal atopic dermatitis, 1.72 for maternal asthma, and 1.23 for paternal asthma. Atopic dermatitis in the child was associated with an increased risk of subsequent respiratory syncytial virus hospitalization among infants < 6 months of age. Infrequent wheezing was associated with a relative risk of subsequent respiratory syncytial virus hospitalization of 2.98 and recurrent wheezing with a relative risk of 5.90. These associations were present also if infants with medical risk factors were excluded from the analysis. CONCLUSIONS. Asthmatic disposition and wheezing were strong determinants of subsequent respiratory syncytial virus hospitalization in Danish children < 18 months of age.