High prevalence of asthma and related symptoms in teenagers in northern Sweden.

Recent reports have suggested an increased asthma prevalence in the Nordic countries. The prevalence of asthma and related symptoms from lower airways in Umeå, Northern Sweden, was investigated in 1987. We used a questionnaire and a skin prick test in 1,112 teenagers. Individuals with symptoms or positive skin prick tests were examined further. The clinical examination included an interview, a ventilatory lung function test, serum specific immunoglobulin E (IgE) test, and a physical examination. Individuals with symptoms from the lower airways underwent a methacholine inhalation test. Asthma was defined as recurrent attacks of dyspnoea and/or wheezing, triggered by known stimuli (excluding infections), and at least one of the following: signs of obstructive airways at examination or provocation concentration giving a 20% fall in forced expiratory volume in one second (PC20) < 8 mg.ml-1. Using this definition, the prevalence of asthma was 6.8%, with a significantly higher prevalence in girls (9.6%) than in boys (4.1%). Furthermore, 16.4% had dyspnoea, wheeze or prolonged cough but did not fulfil our criteria for asthma. The prevalence of asthma and of symptoms from lower airways is higher than has previously been found in Sweden.