Peripheral blood leukocyte count and respiratory symptoms

The relationship of peripheral blood leukocyte count to respiratory symptoms was explored in data from the Second Annual National Health and Nutrition Survey (NHANES II). The study sample consisted of 9237 white and nonwhite US adults between the ages of 30 and 74 years. Three respiratory symptom outcomes were utilized: physician-diagnosed chronic cough and chronic bronchitis and self-reported frequent wheeze apart from colds or flu in the past 12 months. Peripheral blood leukocyte counts were performed using a Coulter counter, model FN. Logistic regression analysis was performed for each of the three respiratory symptom outcomes controlling for age, race, gender, and cigarette-years of smoke exposure. The peripheral blood leukocyte count was a significant predictor for each symptom. For a standard deviation increase in the log leukocyte count, the relative odds of wheezing was 1.93 (95% confidence level [CI], 1.47 to 2.52); for chronic cough, 2.29 (95% CI, 1.74 to 3.00); and for bronchitis, 2.44 (95% CI, 1.77 to 3.35). Analyses restricted to never smokers gave similar results. These data suggest that peripheral blood leukocyte count correlates with respiratory symptoms and are consistent with the hypothesis that the leukocyte count is a serum marker of inflammation.