Determinants of percent predicted FEV1 in current asthmatic subjects.

We analyzed the determinants of the percent predicted FEV1 of a large group of diagnosed asthmatic subjects in the Tucson Study of Airway Obstructive Diseases. The 261 subjects were 6 to 88 years old, and 150 (57.5 percent) were female. Although 29.1 percent of the subjects were current smokers and 24.1 percent were ex-smokers, we found that pack-years of smoking was not related to lung function. In addition, age of onset of disease, duration of asthma, eosinophil count, serum IgE level, and allergy skin test reactivity status did not influence the %FEV1. We did find that both severity of wheezing and age of the subject related significantly to %FEV1, and an interaction term of these two variables replaced wheeze and age in the multiple regression equation. Current physician-diagnosed chronic bronchitis and the reported severity of exertional dyspnea also related to %FEV1.