Aim: Epidemiological data and reports on the prevalence and burden of preschool asthma are mainly based on questionnaires and generally give a prevalence of above 6% in Sweden. In this study we used other ways of studying the prevalence, risk factors and the use of healthcare services in a defined region. Methods: The catchment area included 9410 children aged 0-6 y. All outpatient clinics had computerized records of patients and visits to the outpatient clinic could be studied as well as admissions to hospital for asthma between 1988 and 1998. Results: According to patients’record data, the prevalence of doctor-diagnosed asthma was 4.5% in 1998. Seventy-nine percent of recorded patients are seen outside the hospital, thus the burden of asthma for the health system is mainly on the outpatient clinics. Admissions and especially readmissions to the hospital have decreased during the past decade. One-third of the children with newly diagnosed asthma had recurring exacerbations and risk for persistent asthma.
Conclusions: The prevalence of doctor-diagnosed asthma as measured by total mapping in a region is lower than that reported from questionnaire-based studies. Hospital admissions for preschool asthma have decreased possibly as a result of improved medical care in the paediatric outpatient clinics where asthma is a dominating diagnose. In one-third of identified new asthmatics, there is a high risk of developing persistent asthma.