Early Predictors of Mortality in Patients with COPD, in Relation to Respiratory and Non-Respiratory Causes of Death - A National Register Study.

Background: Both single factors and composite measures have been suggested to predict mortality in patients with chronic obstructive pulmonary disease (COPD) and there is a need to analyze the relative importance of each variable. Objective: To explore the predictors of mortality for patients with COPD in relation to respiratory, cardiac, and malignant causes, as well as all causes of death. Methods: After merging the Swedish Respiratory Tract Register (SRTR) and the Swedish Cause of Death Register, patients with respiratory, cardiac, and other causes of death were identified. Demographic and clinical variables from the deceased patients' first registration with the SRTR were compared. Three univariable and multivariable Cox proportional hazards regression analyses were conducted for different causes of death, with time from first registration to either death or a fixed end date as dependent variable, and variables regarding demographics, respiration, and comorbidities as independent variables. Results: In the multivariable Cox models, mortality for patients with all causes of death was predicted by older age 1.79 (CI 1.41, 2.27), lower percentage of predicted forced expiratory volume in 1 second (FEV1 %) 0.99 (CI 0.98, 0.99), lower saturation 0.92 (CI 0.86, 0.97), worse dyspnea 1.48 (CI 1.26, 1.74) (p<0.002 to p<0.001), less exercise 0.91 (CI 0.85, 0.98), and heart disease 1.53 (CI 1.06, 2.19) (both p<0.05). Mortality for patients with respiratory causes was predicted by higher age 1.67 (CI 1.05, 2.65) (p<0.05), lower FEV1% 0.98 (CI 0.97, 0.99), worse dyspnea 2.05 (CI 1.45, 2.90), and a higher number of exacerbations 1.27 (CI 1.11, 1.45) (p<0.001 in all comparisons). For patients with cardiac causes of death, mortality was predicted by lower FEV1% 0.99 (CI 0.98, 0.99) (p=0.001) and lower saturation 0.82 (CI 0.76, 0.89) (p<0.001), older age 1.46 (CI 1.02, 2.09) (p<0.05), and presence of heart disease at first registration 2.06 (CI 1.13, 3.73) (p<0.05). Conclusion: Obstruction predicted mortality in all models and dyspnea in two models and needs to be addressed. Comorbidity with heart disease could further worsen the COPD patient's prognosis and should be treated by a multidisciplinary team of professional specialists.