These investigators followed a large birth cohort with the use of questionnaires, lung-function tests, and allergy skin tests from the age of 3 to 26 years. Almost three quarters of the study participants had wheezing at one point in the follow-up, and 15 percent had wheezing at all points in the follow-up. Clinical data on a large birth cohort. The increase in the prevalence of wheezing disorders, whether or not they are labeled as asthma, could be related to an increased incidence or an increased persistence of asthma. 1 , 2 Studies of the natural history of asthma have often focused on selected populations. However, the outcomes in children referred to university clinics 3 , 4 or selected in high-risk cohorts 5 may not reflect the outcomes in the general population, since the initial selection criteria may predetermine the risk factors for persistence or relapse. 6 Most children attending asthma specialty clinics who have been followed have had atopy, with frequent symptoms and airway hyperresponsiveness, . . .