Abstract
Early, mild and young COPD concepts are not clearly defined and are often used interchangeably to refer to the onset of the disease. Objective: To describe and compare the characteristics of mild, young and early COPD in a large sample of COPD from primary and secondary care. Methods: Pooled analysis of individual data from four multicenter observational studies of patients with stable COPD (≥40 years, FEV(1)/FVC < 0.7, smoking ≥ 10 pack-years). Mild COPD was defined as FEV(1)% ≥ 65%; young COPD as <55 years; and early COPD as <55 years and smoking ≤ 20 pack-years. The relationship between FEV(1)(%), age and pack-years was analyzed with linear regression equations. Results: We included 5468 patients. Their mean age was 67 (SD: 9.6) years, and 85% were male. A total of 1158 (21.2%) patients had mild COPD; 636 (11.6%) had young COPD and 191 (3.5%) early COPD. The three groups shared common characteristics: they were more frequently female, younger and with less tobacco exposure compared with the remaining patients. Early COPD had fewer comorbidities and fewer COPD admissions, but no significant differences were found in ambulatory exacerbations. In linear regression analysis, the decline in FEV(1)(%) was more pronounced for the first 20 pack-years for all age groups and was even more important in younger patients. Conclusions: Mild, young and early COPD patients were more frequently women. The steepest decline in FEV(1)(%) was observed in individuals <55 years and smoking between 10 and 20 pack-years (early COPD), which highlights the importance of an early detection and implementation of preventive and therapeutic measures.