Biomarkers of systemic inflammation and depression and fatigue in moderate clinically stable COPD

Introduction: COPD is an inflammatory disease with major co-morbidities. It has recently been suggested that depression may be the result of systemic inflammation. We aimed to explore the association between systemic inflammation and symptoms of depression and fatigue in patients with mainly moderate and clinically stable COPD using a range of inflammatory biomarkers, 2 depression and 2 fatigue scales. Method: We assessed 120 patients with moderate COPD (FEV(1)% 52, men 62%, age 66). Depression was assessed using the BASDEC and CES-D scales. Fatigue was assessed using the Manchester COPD-fatigue scale (MCFS) and the Borg scale before and after 6MWT. We measured systemic TNF-alpha, CRP, TNF-alpha-R1, TNF-alpha-R2 and IL-6. Results: A multivariate linear model of all biomarkers showed that TNF-alpha only had a positive correlation with BASDEC depression score (p = 0.007). TNF-alpha remained positively correlated with depression (p = 0.024) after further adjusting for TNF-alpha-R1, TNF-alpha-R2, 6MWD, FEV(1)%, and pack-years. Even after adding the MCFS score, body mass and body composition to the model TNF-alpha was still associated with the BASDEC score (p = 0.044). Furthermore, patients with higher TNF-alpha level (> 3 pg/ml, n = 7) had higher mean CES-D depression score than the rest of the sample (p = 0.03). Borg fatigue score at baseline were weakly correlated with TNF-alpha and CRP, and with TNF-alpha only after 6MWT. Patients with higher TNF-alpha had more fatigue after 6MWD (p = 0.054). Conclusion: This study indicates a possible association between TNF-alpha and two frequent and major co-morbidities in COPD; i.e., depression and fatigue.