This research is being done to study mechanisms of progression of COPD and to develop treatments for it. The investigators are doing the present study to identify people age 40 and older with mild to moderate COPD who will qualify for such studies to include in a database. The study will include establishing a screening evaluation or characterization of the following two studies:

• Emphysema Progression in COPD- Losartan's Effects on Airway Parameters - NA_00009980
• Sleep-Related Physiology and Inflammation in Chronic Obstructive Pulmonary Disease - NA_00001771

This is a program to recruit and screen participants for clinical trials or more detailed observational studies of COPD. There are no interventions or comparative results to be published from this study.

Inclusion Criteria:

• Age 40 years and older, either sex
• Mild to moderate COPD (FEV1/Forced vital capacity (FVC) ratio ≤ 0.70, FEV1 30-70% predicted, Diffusing capacity of the lungs for carbon monoxide (DLCO) ≥35% predicted)
• On stable maintenance therapy for 2 months
• Current or former smoker (patient report of at least a 10 pack-year history)
• Ability to understand and willingness to sign consent documents

Exclusion Criteria:

• COPD exacerbation requiring treatment within past 6 weeks
• Untreated arterial hypertension (systolic blood pressure > 140 mm Hg, diastolic blood pressure > 90 mm Hg)
• Decompensated heart failure
• Myocardial infarction within past 3 months or ever
• Evidence of interstitial, occupational or chronic infectious lung disease
• Renal dysfunction
• Supplemental oxygen > 2 liters/m at rest
• Failure to keep screening appointments

Both Male and Female 40 years and older