Fig. 1From: Risk factors for COPD exacerbations in inhaled medication users: the COPDGene study biannual longitudinal follow-up prospective cohortStudy subjects. The COPDGene cohort was narrowed to those with LFU data available, then narrowed to subjects with a diagnosis of COPD by GOLD criteria, then to those taking medications. These subjects were divided into four exclusive groups based on medication use, as defined in the Methods section. Exacerbators had one or more exacerbations per year, non-exacerbators had zero exacerbations per year, subjects with between 0 and 1 exacerbations per year were not classified. LFU = Longitudinal follow-up; FEV1/FVC = ratio of forced expiratory volume in one second to forced vital capacityBack to article page