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-month, and 12-month follow-up, patients completed the Beck Depression Inventory, and inflammation markers (high-sensitivity C-reactive protein [HsCRP], interleukin (IL)-1β, IL-6, IL-10, and tumor necrosis factor α) 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, confidence interval [CI] = 0.4-1.4) and 6-month follow-up (β = 1.1, CI = 0.3-2.0), and between IL-1β and depressive symptoms at 6-month follow-up (β = 1.3, CI = 0.8-1.8) and 12-month follow-up (β = 1.2, CI = 0.4-1.9). Inflammation makers (HsCRP, IL-6, IL-1β, IL-10, and tumor necrosis factor α) at baseline were not associated with depressive symptoms at follow-up and vice versa. CONCLUSIONS: 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.