ASTHMATIC RISK-FACTORS AND BRONCHIAL REACTIVITY IN NON-DIAGNOSED ASTHMATIC ADULTS

Specific respiratory signs and symptoms are thought to occur prior to diagnoses of asthma as part of the natural history. These signs and sy mptoms include: high IgE, a history of wheezing symptoms, and/or exces sive declines in lung function. The first two are thought to distingui sh asthma from other airway obstructive diseases (AOD). To predict sub sequent AOD, twelve years of follow-up (1972-84) data from the Tucson longitudinal epidemiological study of AOD in a community population we re evaluated on 687 subjects aged 19-70 years on entry. To determine t he likelihood that non-asthmatics that have these specific risk factor s would have marked or intermediate bronchial reactivity to methacholi ne, an experimental study was performed. This was done in 1984-85 in a robust, efficient post-hoc stratified sample of male subjects ages 30 -55 from the population followed from 1972. They were subsequently fol lowed through 1991. Persistent symptoms best predicted final pulmonary function and new diagnosed AOD in subjects in the population. Previou sly diagnosed AOD also predicted lower pulmonary function. The experim ental results indicate that predisposition to reactivity appears likel y without the presence of diagnosed asthma. Further, the experimental subjects with high risk had increased symptomatology and decreased lun g function when tested at follow-up; nor all of the reactivity was exp lained by these factors. An attempt to predict reactivity by physician evaluation and special questionnaire was not fruitful. In addition, w heeze per se often disappeared without later evidence of asthma (or AO D) diagnosis, questioning some international tendencies to label all w heeze as asthma. Thus, high IgE significantly predicted bronchial resp onsiveness, but high IgE and symptoms are neither necessary nor suffic ient. Also, both preclinical and clinical asthma predict eventual low lung function.