Nine-year follow-up of interleukin 6 in chronic obstructive pulmonary disease – complementary results from previous studies

Abstract

Background: Systemic manifestations of chronic obstructive pulmonary disease (COPD) are related to increased systemic inflammatory process; however, it is not entirely clear how much they are related and how the systemic inflammation, in particular interleukin-6 (IL-6), is associated with exacerbation and mortality risk. Objective: To evaluate the role of IL-6 in COPD patients over nine years. Study Design and Methods: A total of 133 COPD patients were assessed at baseline between 2004 and 2006 and reassessed after three and nine years through clinical evaluation, comorbidities, hematological blood count and IL-6 analysis. Results: After nine years, 19 patients lost the follow-up and were not possible to identify the date of death of four patients; 12 refused to participate and 1 could not be involved due to recurrent exacerbations. Therefore, 33 patients were included in the reassessment after nine years of follow-up and 92 patients were included in the Cox mortality analysis with IL-6 as a time-dependent covariate. Regarding the inflammatory profile, in patients who survived after nine years, there was a significant increase in IL-6 [0.4 (0.2–0.8) vs 5.7 (3.4–11) pg/mL; p < 0.001] and reduction in lymphocyte count [2.1 (1.6–2.4) vs 1.4 (1.2–2.1)10^9/L; p < 0.01] with an increase in the neutrophil/lymphocyte ratio (2.0 ± 0.7 vs 2.7 ± 1.2; p = 0.003). The Cox mortality model did not show a statistical significance influence of IL-6 assessed during the follow-up. Conclusion: There was a progressive increase in IL-6 during the follow-up, however, without influence on mortality.