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The prevalence of symptoms of asthma, allergic rhinitis, and atopic eczema in children in the United Kingdom ranks among the highest in the world.1 The evidence from most repeat surveys is that prevalence has increased over the past three decades,2 but the most recent of these studies observed that from 1991 to 1998 the increase was confined to milder symptoms of asthma.3 Since the early 1990s the incidence of asthma episodes presenting to general practitioners, and of hospital admissions, has fallen substantially.2
In 1995, as part of the international study of asthma and allergies in childhood (ISAAC), we surveyed symptoms of atopic disease in England, Scotland, Wales, and the offshore islands of Guernsey, Isle of Man, and Jersey.4,5 A self completed questionnaire which adhered to the core ISAAC protocol was administered to secondary school children aged 12-14 in school years 8 and 9 (S2 and S3 in Scotland). In 2002 the survey was repeated in Scotland, Wales, and the islands in the same school years, using the same questionnaire and procedures in the same period of the year and, mostly, in the same schools. In England, only the schools in the South East Region were surveyed a second time. The table shows the changes in prevalence over the seven years from 1995 to 2002.
Overall, the prevalence of any wheezing or whistling in the chest in the past 12 months fell from 34% to 28% (19% relative reduction). Even larger proportional falls were observed for frequent attacks (35%) and speech limiting attacks (24%). Large reductions were also observed for symptoms of allergic rhinoconjunctivitis (16%) and atopic eczema (30%). The proportion of children reporting “ever” having had “asthma” or “eczema” increased (26% and 15%), as did the lifetime prevalence of “hay fever” (8%). Trends in the four regions were similar.
The fall in prevalence is consistent with other sources. From 1995 to 2000, hospital admissions for asthma fell by 20.4% in 10-14 year olds in England, Scotland, and Wales combined (see table). From 1995 to 2002, in 10-14 year olds in a sample of 75 English and Welsh practices, visits to a general practitioner for episodes of asthma decreased by 47% (from 38.3 to 20.4 per 1000). Recently released data from the health survey for England shows that from 1997 to 2001, the 12 month prevalence of wheezing in 10-14 year olds, based on parental reporting, fell by 18% (from 17.4% to 14.2%).
The burden of self reported asthma and other allergic diseases among adolescents has changed substantially for the better in recent years throughout the British Isles. These trends correspond to those seen in the 10-14 year age group in hospital admissions, consultations with general practitioners, and parentally reported symptoms in the health survey for England. Just as we do not know why the prevalence of symptoms of asthma has increased since the 1950s, we do not know why it should now be decreasing. The increased use of effective treatment, especially inhaled steroids, is likely to have been important in reducing the severity of episodes, but this is unlikely to explain the decrease in mild wheeze symptoms, which is more consistent with a fall in the underlying prevalence. The most likely explanation for the paradoxical increase in prevalence of the label of asthma is that it is applied to increasingly milder disease.
This article was posted on bmj.com on 17 March 2004: http://bmj.com/cgi/doi/10.1136/bmj.38057.583727.47
Data on GP consultations from the weekly returns service were provided by Douglas Fleming of the RCGP Research Unit, Manchester. Hospital admissions data from the hospital episode systems of England and Wales and the Scottish hospital inpatient system, and prevalence data from the health survey for England, were extracted by the Ramyani Gupta at the Lung and Asthma Information Agency, Department of Community Health Sciences, St George's Hospital Medical School, London.
Contributors: See bmj.com
Funding: National Asthma Campaign (South East England study), Chief Scientist's Office, Scottish Executive Health Department (Scottish study), Wolfson Intercalated Awards Programme (Welsh study), and DHSS Isle of Man.
Competing interests: None declared.
Ethical approval: Ethics approval was obtained from the respective multiple and local research ethics committees.