Epidemiologic observations on eosinophilia and its relation to respiratory disorders.

The percentage of eosinophils (%EOS), determined from a differential blood smear, was measured in 2,311 subjects enrolled in a general population study in Tucson, Arizona. A subgroup of 290 subjects was tested in more detail during a later evaluation in which absolute eosinophil counts, leukocyte counts, and nasal smears for eosinophils were obtained. In men, but not in women, there was a significant tendency for the %EOS to decrease with age. The highest %EOS was noted during the months of February through May, the time when most plants in this region are in bloom. Blood eosinophils were significantly related to allergy skin test reactivity, circulating IgE concentrations, several respiratory symptoms and disease diagnoses, as well as to reduced ventilatory function. Among subjects younger than 55 yr of age, however, ventilatory function was significantly low, and symptom rates increased only when there was allergy skin test reactivity in addition to eosinophilia. Neither allergy skin test reactivity nor eosinophilia alone was related to ventilatory function in this age group. Among older subjects, blood eosinophilia was associated with definite impairment of ventilatory function, regardless of skin test reactivity and independent of smoking habits. The presence of eosinophilia identified a predominantly female group of elderly nonsmokers with markedly impaired ventilatory function. These subjects appeared to fall into the clinical category of "asthmatic bronchitis".