Association of sleep apnea and obstructive airway disease using three different definitions: National Clinical Guidance Centre (NICE) (FEV1/FVC < 0.7 and FEV1 < 80% predicted), “fixed-ratio” FEV1/FVC < 0.7, Global Initiative for Chronic Obstructive Lung Disease (GOLD) (FEV1/FVC < 0.7: mild if FEV1 ≥ 80% predicted, moderate to severe if FEV1 < 80% predicted). Sensitivity analysis was conducted using a ratio of FEV1/FVC < 0.65. Sleep apnea was defined as an apnea-hypopnea index ≥ 15. Models were adjusted for age, race, study site, body mass index, neck circumference, and smoking status. FEV1, forced expiratory volume in one second; FVC, forced vital capacity.