Trends in the epidemiology of asthma in England: a national study of 333,294 patients

Summary Background Observations in the UK at the end of the last century found increasing trends of asthma prevalence over time. However, it has been reported that the number of new cases of asthma presenting to general practice has declined, especially among younger children. Aim To study national trends in the epidemiology of asthma. Methods A cross-sectional observation analysis was performed using the QRESEARCH database, which is one of the world's largest national aggregated health databases containing records from 422 English practices yielding 30 million patient-years of observation. Data was extracted on 333,294 individuals with a recorded diagnosis of asthma and calculated annual age–sex standardized incidence, lifetime period prevalence and asthma-related prescribing rates for each year from 2001–2005. Results The incidence rate of asthma decreased in all patients (2001: 6.9 (95% confidence intervals [CI] 6.8–7.0); 2005: 5.2 (95% CI 5.1–5.3) per 1000 patient-years, p<0.001), but most particularly in children under 5 years of age (–38.4%) where a decrease in the lifetime prevalence of asthma (–34.3%) was also found. However, the lifetime prevalence rate of asthma for adults increased (15–44 years: 23.3%; 45–64 years: 27.7%; >65 years: 21.5%) with an estimated 5,658,900 (95% CI 5,639,700–5,678,200) or approximately one person in nine having being diagnosed with asthma in England. The number of asthma-related prescriptions also increased over the study period (17.1%), such that in 2005 an estimated 32,577,300 (95%CI 32,531,600–32,623,000) prescriptions were issued. Conclusions This large national study reveals that the rate of new diagnoses of asthma appears to have passed its peak; however, the number of adults with a lifetime asthma diagnosis continues to rise. Whether these trends are genuine or are a result of the introduction of incentives and guidelines to improve identification and recording of asthma or changing diagnostic trends is a question with important public health implications and one, therefore, that warrants detailed further enquiry.