Admission to hospital for bronchiolitis in England: trends over five decades, geographical variation and association with perinatal characteristics and subsequent asthma

Abstract

Background: Admission of infants to hospital with bronchiolitis consumes considerable healthcare resources each winter. We report an analysis of hospital admissions in England over five decades.

Methods: Data were analysed from the Hospital In-Patient Enquiry (HIPE, 1968-1985), Hospital Episode Statistics (HES, 1989-2011), Oxford Record Linkage Study (ORLS, 1963-2011) and Paediatric Intensive Care Audit Network (PICANet, 2003-2012). Cases were identified using International Classification of Diseases (ICD) codes in discharge records. Bronchiolitis was given a separate code in ICD9 (used in England from 1979). Geographical variation was analysed using Local Authority area boundaries. Maternal and perinatal risk factors associated with bronchiolitis and subsequent admissions for asthma were analysed using record-linkage.

Results: All-England HIPE and HES data recorded 468 138 episodes of admission for bronchiolitis in infants aged <1 year between 1979 and 2011. In 2011 the estimated annual hospital admission rate was 46.1 (95% CI 45.6 to 46.6) per 1000 infants aged <1 year. Between 2004 and 2011 the rates rose by an average of 1.8% per year in the all-England HES data, whereas admission rates to paediatric intensive care changed little (1.3 to 1.6 per 1000 infants aged <1 year). A fivefold geographical variation in hospital admission rates was observed. Young maternal age, low social class, low birth weight and maternal smoking were among factors associated with an increased risk of hospital admission with bronchiolitis.

Conclusions: Hospital admissions for infants with bronchiolitis have increased substantially in recent years. However, cases requiring intensive care have changed little since 2004.

Keywords: Epidemiology; General Paediatrics; Infectious Diseases; Intensive Care; Respiratory.

Figure 1

Point estimates for the annual average episode and person-based hospital admission rate for bronchiolitis per 1000 infants aged <12 months from 1979 to 2011, episode-based combined acute bronchitis and bronchiolitis rates from 1965 to 1979 and bronchitis before 1965. Person-based hospital admission rates for males were consistently higher than females (see supplementary material online). 128×63 mm (300×300 DPI). HES, Hospital Episode Statistics; HIPE, Hospital In-Patient Enquiry; ORLS, Oxford Record Linkage Study.

Figure 2

PICU admissions with bronchiolitis and all-causes from 2004 to 2012. (A) All-cause and bronchiolitis admission rates per 1000 infants. (B) Mean age (months with 95% CI) at admission for bronchiolitis. Between 2004 and 2006 the mean age rose significantly (**p=0.0004, two-tailed Mann–Whitney). In more recent years the mean age has fallen significantly between 2008 and 2012 (*p=0.04, two-tailed Mann–Whitney). 124×62 mm (300×300 DPI). PICU, paediatric intensive care unit.

Figure 3

National variation in person-based bronchiolitis hospital admission rates, 1999–2011. Bronchiolitis admission rates per 1000 infants aged <1 year, as analysed using Hospital Episode Statistics, both sexes, mapped using the boundaries of each Local Government Area. 135×173 mm (72×72 DPI).