Peripheral Blood Eosinophils and Nine Years Mortality in COPD Patients

BACKGROUND: Eosinophil counts increase during chronic obstructive pulmonary disease (COPD) exacerbation and influence the response to different agents (such as inhaled and systemic corticosteroids), as well as increase the production of other inflammatory cytokines. However, few studies have evaluated the association between peripheral blood eosinophils with mortality rate. OBJECTIVE: To evaluate the association between peripheral blood eosinophils and mortality rate in COPD patients over a nine-year period. STUDY DESIGN AND METHODS: This cohort included 133 COPD patients assessed at baseline by spirometry, pulse oximetry (SpO(2)), complete blood count, body composition, dyspnea intensity [Modified Medical Research Council (mMRC)] and the six-minute distance test (6MWD). The Kaplan–Meier curve followed by a Log rank test was used to evaluate mortality rate related to eosinophil cutoff point categorization. Multivariate Cox regression analysis was performed to identify the association between eosinophils and mortality with all subjects evaluated at baseline, adjusted for age, gender, mMRC, 6MWT, forced expiratory volume in the first second (FEV(1)) and SpO(2). RESULTS: Nineteen patients did not complete follow-up and it was not possible to identify the date of death in four others. Therefore, 110 patients were included in the analysis. At baseline, 81% presented ≥150 eosinophil cells and 72% presented ≥2%. We identified a three-fold higher risk of death in those with <2% eosinophils and <150 cells. We did not identify statistical differences when using other cutoff points. CONCLUSION: The decrease in number of peripheral eosinophils, with cutoff points at 2% and 150 cells, may be associated with a higher risk of death in COPD patients over nine years.