Population demographics and risk factors of individual sites and for whole cohort.

§Doctor Diagnosis of AO = presence of self reported prior diagnosis of either ever-asthma, or asthmatic bronchitis, or allergic bronchitis, or COPD, or emphysema, or chronic bronchitis. Data for Age, BMI, Packyears, and Spirometry results are expressed in mean(SD); All others are expressed as % of group(SE) and are weighted to the local population. BMI = Body-mass index;
†% predicted values = maximum values/predicted values(NHANES)*100;
*One-Way ANOVA, alpha = 0.05;
#Chi-Square Test.
&post bronchodilator responses: % change in FEV1 or FVC after bronchodilator relative to pre-bronchodilator value.