15, 19, 20 Although originally designed as a single-visit cross-sectional study, the COPDGene cohort was converted into a longitudinal study in its second year. ![]() Additional characteristics of the study population and study methodology have been described previously. At the time of enrollment, all subjects were 45 to 80 years old, had a history of smoking for at least 10 pack-years, and had not had an acute respiratory exacerbation for at least 30 days prior to enrollment. Subjects were enrolled from January 2008 to April 2011. The current analysis was approved by the National Jewish Health Institutional Review Board (AS-1887). 19 COPDGene was approved by the institutional review board at each participating center, and all subjects provided written informed consent. The COPDGene study consists of 10,300 subjects at 21 centers across the United States. The Genetic Epidemiology of COPD (COPDGene) study has multiple unique features that make it ideal for studying these unmet needs: (1) it is one of the largest prospective studies of subjects with COPD and also those who are at risk of, but do not meet the spirometric criteria for, COPD (2) it includes a large number of blacks and (3) its subjects have been well characterized clinically and by quantitative high-resolution chest CT scan. 16‐ 18 Most of these cross-sectional studies did not include smokers without COPD and few contained a large number of underrepresented populations (eg, blacks). 15 Age, sex, BMI, a history of cardiovascular disease, theophylline use, and a lack of influenza vaccine are also independent risk factors. 10‐ 12 Multiple cross-sectional studies have identified common factors associated with acute exacerbations of COPD such as severe airflow obstruction, poor health-related quality of life, 13 gastroesophageal reflux, 14 and chronic bronchitis. These episodes are referred to as acute exacerbations of COPD and are associated with decreased quality of life, 7, 8 increased lung function decline, 9 and higher mortality. Most current knowledge of acute episodes of respiratory disease in current and former smokers comes from studies of patients with COPD. 1 This large understudied group may pose a significant, underrecognized health-care burden, and there is an unmet need to define and quantitate their risk of acute episodes of respiratory disease. Furthermore, most studies of acute episodes of respiratory disease in current and former smokers include only patients with significant airflow limitation (ie, moderate or more severe COPD) despite population surveys indicating that most current and former smokers do not meet the spirometric criteria for COPD. 3 The current medical knowledge and literature are confusing because these acute episodes of respiratory disease have multiple terminologies such as acute bronchitis, 4 exacerbations of chronic bronchitis, 5 and acute exacerbations of COPD, 6 despite the fact that the pathophysiology (bacterial and viral infections) and treatment (corticosteroids and antibiotics) are similar. 2 The cost of treating these acute episodes exceeds $30 billion per year. ![]() 1 Many of these people experience episodes of acute respiratory disease characterized by increased or new shortness of breath, cough, and/or change in sputum quantity or quality. More than 100 million people have a smoking history in the United States, and 20% of the population currently smokes.
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