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.