Health Status Measurements: During each visit, study participants will complete the SGRQ in person. The SGRQ was chosen because it has excellent internal consistency (Cronbach’s alpha coefficient ≥ 0.76), reliability (intraclass correlation coefficient of ~85% of responses measured 6 months apart), and is an independent predictor of future risk of exacerbations and mortality in COPD. Clinically relevant thresholds for SGRQ are considered to be score changes of ≥ 4.0 units.