Household tobacco smoke and admission weight predict severe bronchiolitis in infants independent of deprivation: prospective cohort study.

To examine demographic, environmental and clinical factors associated with severe bronchiolitis in infants admitted to hospital and quantify the independent effects of these factors.Prospective cohort study.Alder Hey Children's Hospital, Liverpool, United Kingdom.378 infants admitted to hospital with a diagnosis of bronchiolitis, of whom 299 (79%) were antigen positive to respiratory syncytial virus (RSV).Severity of disease during admission, defined as "no need for supplemental oxygen" (reference group), "any need for supplemental oxygen" and "any need for mechanical ventilation".Univariate analysis found male sex (p = 0.035) and tobacco smoking by a household member (p<0.001) were associated with need for both supplemental oxygen and mechanical ventilation. Premature birth, low gestation, low birth weight, low admission weight and low corrected age on admission were also associated with need for mechanical ventilation (all p≤0.002). Deprivation scores (IMD 2004) were significantly higher in households where a member smoked compared to non-smoking households (p