Preschool respiratory hospital admissions following infant bronchiolitis: a birth cohort study

<h4>Background</h4>Bronchiolitis causes significant infant morbidity worldwide from hospital admissions. However, studies quantifying the subsequent respiratory burden in children under 5 years are lacking.<h4>Objective</h4>To estimate the risk of subsequent respiratory hospital admissions in children under 5 years in England following bronchiolitis admission in infancy.<h4>Design</h4>Retrospective population-based birth cohort study.<h4>Setting</h4>Public hospitals in England.<h4>Patients</h4>We constructed a birth cohort of 613 377 infants born between 1 April 2007 and 31 March 2008, followed up until aged 5 years by linking Hospital Episode Statistics admissions data.<h4>Methods</h4>We compared the risk of respiratory hospital admission due to asthma, wheezing and lower and upper respiratory tract infections (LRTI and URTI) in infants who had been admitted for bronchiolitis with those who had not, using Cox proportional hazard regression. We adjusted hazard ratios (HR) for known respiratory illness risk factors including living in deprived households, being born preterm or with a comorbid condition.<h4>Results</h4>We identified 16 288/613 377 infants (2.7%) with at least one admission for bronchiolitis. Of these, 21.7% had a further respiratory hospital admission by age 5 years compared with 8% without a previous bronchiolitis admission (HR (adjusted) 2.82, 95% CI 2.72 to 2.92). The association was greatest for asthma (HR (adjusted) 4.35, 95% CI 4.00 to 4.73) and wheezing admissions (HR (adjusted) 5.02, 95% CI 4.64 to 5.44), but were also significant for URTI and LRTI admissions.<h4>Conclusions</h4>Hospital admission for bronchiolitis in infancy is associated with a threefold to fivefold risk of subsequent respiratory hospital admissions from asthma, wheezing and respiratory infections. One in five infants with bronchiolitis hospital admissions will have a subsequent respiratory hospital admission by age 5 years.