Abstract
We have followed 1037 children born between 1 April 1972 and 31 March 1973 in Dunedin, New Zealand, with respiratory assessments at ages 9, 11, 13, 15 and 18 years. Almost all performed spirometry, and most performed methacholine challenge at ages 9-15 whether or not symptoms were reported. At 18, all subjects were tested before and after inhaled salbutamol. The prevelance of diagnosed current asthma increased with age, as did reporting of current wheezing. Airway responsiveness to methacholine (or salbutamol in those with airflow obstruction at baseline) declined with age. The discrepancy between diagnosed asthma or wheezing symptoms, and measurements of airway responsiveness, became more evident with age. over 16% of 18-year-olds reported asthma, most of whom received treatment. Almost 50% of those reporting asthma at 18 showed >10% increase in FEV1after inhaled salbutamol on the day of assessment, suggesting a true diagnosis of asthma. The study confirms a high prevalence of asthma and asthma-like symptoms in young New Zealanders, although concomitant airway responsiveness was often not detected. The anticipated decrease in current asthma, wheezing symptoms and need for treatment during adolescence was not found.