AIRWAY RESPONSIVENESS IN YOUNG BLACK-AND-WHITE WOMEN

The prevalence and severity of asthma appears to be greater in blacks than in whites. To determine if racial differences in airway responsiv eness may explain these findings, methacholine challenge tests from 62 black and 238 white women 20 to 35 yr of age were evaluated. Subjects served as controls for a case-control study of the relation of airway responsiveness and preterm labor. Standardized questionnaires were us ed to obtain information on age, obstetrical history, education, incom e, cigarette smoking, medication use, and respiratory illnesses and sy mptoms. Total serum IgE was measured using a radioimmunoassay. Methach oline challenge testing was performed on all subjects 6 wk after deliv ery, and the provocative dose causing a 20% decrease in FEV1 (PD20) wa s calculated. Black women in the study had more pregnancies and childr en, were younger, less well educated and more impoverished, and report ed greater cigarette smoking and less medication use than did the whit e women. Additionally, black women had higher geometric mean serum IgE levels (blacks: 65.4 IU versus whites: 20.0 IU; p < 0.001), lower FEV 1 (blacks: 2.73 +/-0.38 SD L versus whites: 3.19 +/- 0.39 L; p < 0.001 ), and greater unadjusted airway responsiveness than did white women ( geometric mean PD20: blacks: 28.4 mumol versus whites: 38.8 mumol; p = 0.02). After adjusting for selective demographic and smoking differen ces, a significant additional effect of race on mean PD20 was found. H owever, after adjustment for level of serum IgE and level of FEV1, rac ial differences were no longer apparent. Similar results were found wh en asthmatics were excluded from the analyses (black asthmatics, n = 6 : 9.7% versus white asthmatics, n = 19: 8.0%) and when only subjects w ith heightened airway responsiveness were included in the analyses (bl acks, n = 21: 33.9% versus whites, n = 45:18.9%). These findings sugge st that young black women have a greater degree of methacholine airway responsiveness than do white women of comparable age. Higher levels o f serum IgE and lower levels of lung function in blacks may explain th ese findings.