ObjectiveTo examine the timing and duration of RSV bronchiolitis hospital admission among term and preterm infants in England and to identify risk factors for bronchiolitis admission.DesignA population-based birth cohort with follow-up to age 1 year, using the Hospital Episode Statistics database.Setting71 hospitals across England.ParticipantsWe identified 296618 individual birth records from 2007/08 and linked to subsequent hospital admission records during the first year of life.ResultsIn our cohort there were 7189 hospital admissions with a diagnosis of bronchiolitis, 24.2 admissions per 1000 infants under 1 year (95%CI 23.7–24.8), of which 15% (1050/7189) were born preterm (47.3 bronchiolitis admissions per 1000 preterm infants (95% CI 44.4–50.2)). The peak age group for bronchiolitis admissions was infants aged 1 month and the median was age 120 days (IQR = 61–209 days). The median length of stay was 1 day (IQR = 0–3). The relative risk (RR) of a bronchiolitis admission was higher among infants with known risk factors for severe RSV infection, including those born preterm (RR = 1.9, 95% CI 1.8–2.0) compared with infants born at term. Other conditions also significantly increased risk of bronchiolitis admission, including Down's syndrome (RR = 2.5, 95% CI 1.7–3.7) and cerebral palsy (RR = 2.4, 95% CI 1.5–4.0).ConclusionsMost (85%) of the infants who are admitted to hospital with bronchiolitis in England are born at term, with no known predisposing risk factors for severe RSV infection, although risk of admission is higher in known risk groups. The early age of bronchiolitis admissions has important implications for the potential impact and timing of future active and passive immunisations. More research is needed to explain why babies born with Down's syndrome and cerebral palsy are also at higher risk of hospital admission with RSV bronchiolitis.

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Plaque and saliva samples were obtained from 55 children aged 13–15 years: 23 of them were caries free (group N) while the other 32 had evidence of high-caries activity over the preceding 2 years, with a mean DMFS of 25.9 (group H). The average concentration of calcium in posterior plaque of children in group N was 3.57 μg/mg (dry weight), compared with 1.63 μg/mg for group H. The average concentration of calcium in anterior plaque was 11.55 μg/mg in group N and 2.57 μg/mg in group H. The differences between groups N and H were statistically significant (p < 0.01). Similar significant differences were found between phosphorus levels in plaque. Although the mean levels of both calcium and phosphorus in saliva were higher for group N than for group H, only for phosphorus did the difference reach statistical significance (p < 0.05). The present study therefore shows that levels of both calcium and phosphorus are significantly higher in plaque taken from children with no caries experience than they are in plaque from children who are caries susceptible.

The completeness of recording of hospital birth information varies greatly between hospitals in England but is improving. It may be preferable and valid to construct cohorts from only hospitals with high completeness of recording.