A diagnosis of AE-COPD will incorporate a modification of the definition used by the COPD Clinical Research Network (CCRN). The diagnosis will be made in one of two ways: severe AE-COPD will be defined as a change in respiratory symptoms above the participant's baseline measurements plus evaluation in the emergency room (ER) or requiring hospitalization; or mild-to-moderate AE-COPD will be defined as a change in respiratory symptoms above the participant's baseline measurements and requiring a change in therapy (addition of either antibiotics, oral steroids, or both), but without evaluation in the ER or hospitalization. In the latter case, therapy could be changed either at the advice of the patient's own caregivers or a study physician based on clinical judgment, or could be self-initiated in the case of participants authorized to do so by their caregiver. A concerted effort will be made to capture these milder AE-COPD during both winter and non-winter seasons.