Association between respiratory syncytial virus hospitalization in infancy and childhood asthma

Introduction Respiratory syncytial virus infection in early childhood has been linked to longer-term respiratory morbidity; however, debate persists around its impact on asthma. The objective was to assess the association between respiratory syncytial virus hospitalization and childhood asthma. Methods Asthma hospital admissions and medication use through 18 years were compared in children with (cases) and without (controls) respiratory syncytial virus hospitalization in the first 2 years of life. All children born in National Health Service Scotland between 1996 and 2011 were included. Results Of 740 418 children (median follow-up: 10.6 years), 15 795 (2.1%) had a respiratory syncytial virus hospitalization at <= 2 years (median age: 143 days). Asthma hospitalizations were three-fold higher in cases than controls (8.4% vs 2.4%; relative risk: 3.3, 95% confidence interval [CI]: 3.1-3.5; P < .0001) and admission rates were four-fold higher (193.2 vs 46.0/1000). Cases had two-fold higher asthma medication usage (25.5% vs 14.7%; relative risk: 1.7, 95% CI: 1.7-1.8; P < .0001) and a three-fold higher rate of having both an asthma admission and medication (4.8% vs 1.5%; relative risk 3.1, 95% CI: 2.9-3.3; P < .0001). Admission rates and medication use remained significantly (P < .001) higher for cases than controls throughout childhood (admissions: >= 2-fold higher; medication: >= 1.5-fold higher). Respiratory syncytial virus hospitalization was the most significant risk factor for asthma hospitalizations +/- medication use (odds ratio: 1.9-2.8; P < .001). Conclusions Respiratory syncytial virus hospitalization was associated with significantly increased rates and severity of asthma throughout childhood, which has important implications for preventive strategies.