Longitudinal associations between inflammation and depressive symptoms in chronic dialysis patients.

OBJECTIVE: Patients undergoing chronic dialysis often display sustained elevations of inflammation markers and also have a high prevalence of depressive symptoms. Although multiple studies demonstrated cross-sectional associations between inflammation markers and depressive symptoms in this patient group, longitudinal associations have not been examined. We therefore investigated whether longitudinal associations exist between inflammation markers and depressive symptoms in chronic dialysis patients.

METHODS: Data of three consecutive measurements of an observational, prospective cohort study among chronic dialysis patients were used. At baseline, 6 months and 12 months follow-up, patients completed the Beck Depression Inventory (BDI) and inflammation markers (HsCRP, IL-1β, IL-6, IL-10, and TNFα) were measured. We examined cross-sectional associations between inflammation markers and depressive symptoms using linear regression models. The longitudinal association between inflammation and depressive symptoms was assessed using a linear mixed model analyses.

RESULTS: A total of 513 patients were included. Cross-sectional associations were found between HsCRP and depressive symptoms at baseline (β= 0.9 (CI: 0.4-1.4)) and 6 months follow-up (β= 1.1 (CI: 0.3-2.0)), and between IL-1β and depressive symptoms at 6 months follow-up (β= 1.3 (CI: 0.8-1.8)) and 12 months follow-up (β= 1.2 (CI: 0.4-1.9)). Inflammation makers (HsCRP, IL-6, IL-1β, IL-10 and TNFa) at baseline were not associated with depressive symptoms at follow-up and vice versa.

CONCLUSION: We confirmed the presence of cross-sectional associations between inflammation markers and depressive symptoms in chronic dialysis patients, but with our longitudinal data we found no longitudinal associations. This supports an associative instead of a causal relationship between inflammation and depressive symptoms.