The aetiology and prevalence of childhood asthma
Asthma is the commonest chronic disorder of childhood. Although the subject of study for over 4,000 years, the aetiology remains elusive and understanding of the subject is beset with problems of definition and methodology. The prevalence throughout the world varies considerably but is generally higher in countries with a western lifestyle, and appears to be increasing. Of many factors postulated to explain this increase, atmospheric pollution has been one of the most widely cited. The aim of the research presented in this thesis was to describe the epidemiology of asthma in the adolescent population in the Highlands of Scotland, a remote, culturally distinct, mainly rural area that covers one third of Scotland. A cross sectional study was undertaken using a questionnaire, supported by objective data from baseline pulmonary function and exercise testing. The prevalence of parent reported asthma in 12 year old children in 1992 (n=1825) was 14%, current wheeze 19%, eczema 14%, and hay fever 19%. Exercise induced bronchospasm was evident in 9%. The highest prevalence of asthma (17%) and exercise induced bronchoconstriction (30%) was reported on the island of Skye. Having found the prevalence to be as high in the relatively unpolluted Highlands as in urban areas of the UK, possible explanations were sought. Studies were undertaken to explore risk factors including family history, associated atopy, place of birth, indoor environment including maternal smoking, diet (with emphasis on antioxidant and fish intake), and immunisation history (including tuberculin status). Although there were some interesting findings, no specific single environmental component was identified as a major factor in the aetiology of asthma. I hope this thesis will provide a baseline of information, which may be of value to others in the future for as Churchill stated "the longer you can look back, the further you can look forward".