Determinants of Exhaled Nitric Oxide Levels in Healthy Non-Smoking African American Adults

Abstract

Asthma is a significant cause of morbidity and mortality for African Americans. Exhaled nitric oxide (FeNO) levels are elevated in asthma and airway levels of NO metabolites regulate airway inflammation and airway diameter. More needs to be known about the factors that regulate FeNO. There is a need for FeNO reference values for African Americans. The objective of this study was to establish reference values and identify factors associated with FeNO levels in healthy African American adults. FeNO was measured in 895 healthy, non-smoking, African Americans between the ages of 18 and 40. FeNO measurements were repeated in 84 subjects. Factors potentially associated with FeNO were measured including blood pressure, height, weight, serum total IgE, ECP, CRP and nitrate. Data on respiratory symptoms including upper respiratory infection (URI) symptoms were collected. Univariate and multivariate analyses of the relationship between these variables and FeNO were performed. In healthy, non-smoking African Americans, FeNO was stable during repeated measurements (rI = 0.81). Gender (p < 0.0001), serum total IgE (p < 0.0001) and current URI symptoms (p = 0.0002) contributed significantly to FeNO variability but together accounted for less than 50% of the variation in FeNO. The high correlation between repeated measurements of FeNO and the low correlation coefficients of known factors associated with FeNO suggest that other factors may contribute substantially to FeNO variability in African Americans. Gender, elevated serum total IgE and current URI symptoms should be considered when evaluating FeNO levels in adults. Importantly, these studies provide FeNO reference values for healthy African American adults.