Establishing the incidence and prevalence of clinician-diagnosed allergic conditions in children and adolescents using routinely collected data from general practices.

BACKGROUND: There remains a need to better characterize the epidemiology of allergic disorders, particularly in relation to describing the incidence, natural history and co-morbidity of allergic conditions.
OBJECTIVES: To estimate the incidence and prevalence of clinician-diagnosed eczema, asthma and rhinitis, alone and in combination, in children and adolescents in the United Kingdom.
METHODS: Using the national General Practice Research Database (GPRD) - one of the largest validated databases of routinely collected healthcare data in the world aggregating 3.6 million individuals - we constructed a retrospective birth cohort of 43,473 children born in the year 1990 and registered with a UK general practice within a year of birth. The cohort was followed until 2008 or the longest available follow-up period to determine the cumulative and age-specific incidence and prevalence rates of clinician-diagnosed eczema, asthma and rhinitis, and an 18-year prevalence of these conditions, alone and in combination.
RESULTS: Eczema had the highest incidence density of 226.9 per 10,000 person-years [95% confidence interval (CI): 225.8-228.0] followed by asthma [136.6;(95% CI: 135.7-137.5)] and rhinitis [61.4;(95% CI: 60.8-62.0)], by the age of 18 years. The incidence densities of suffering from one, two or all three allergic conditions were 323.2 (95% CI: 322.0-324.4), 206.4 (95% CI: 205.7-207.1) and 141.9 (95% CI: 141.4-142.4) per 10,000 person-years, respectively. Among the 24 112 children with a complete 18-year follow-up, eczema had the highest 18-year prevalence of clinician-diagnosed condition at 36.5% (95% CI: 35.9-37.2%) followed by asthma [22.9;(95% CI: 22.3-23.4%)] and rhinitis[11.4;(95% CI: 11.0-11.8%)]. The 18-year prevalence of more than one and all three conditions was 16.1% (95% CI: 15.6-16.6%) and 2.5% (95% CI: 2.4-2.8%), respectively.
CONCLUSIONS: This is one of the first studies to provide national estimates on the age-specific incidence and age-specific prevalence of the major allergic disorders showing clinician-diagnosed eczema, asthma and rhinitis to have high incidence rates in early childhood. A significant proportion of children experience and are diagnosed with multiple allergic conditions in early childhood.