Serum IL-6, albumin and comorbidities are closely correlated with symptoms of depression in patients on maintenance haemodialysis

Background. Depression may be associated with activation of pro-inflammatory cytokines and increased long-term mortality in patients on maintenance haemodialysis (MHD). There are numerous reports regarding the association of depression with inflammatory status, co-morbidities and nutritional condition, but few of these studies have explored the possible correlations between depression, age and economic status. The study explores the possible correlations between depression and demographic, socio-economic, clinical and laboratory variables. Methods. One hundred and forty-six MHD patients (65 males and 81 females, mean age: 63.8 +/- 15.2 years) were enrolled in this cross-sectional study. Demographic and socio-economic status as well as clinical and laboratory variables including co-morbidities were obtained. The self-administered Beck Depression Inventory (BDI) was used to determine the presence or absence of depression symptoms. Biochemical parameters (serum albumin, triglyceride, cholesterol, etc.) and dialysis dosage delivery (Kt/V and urea reduction rate or URR) were examined. All the patients were on high-flux biocompatible dialysers for MHD. The presence of an inflammatory state was assessed by determinations of plasma interleukin-6 (IL-6) levels. Results. The prevalence of depression (BDI >= 14) was 45.9%. In patients found to have symptoms of depression, no statistically significant difference was shown with respect to age, gender, smoking habits or clinical characteristics. However, these patients were more likely to have a number of co-morbidities. They also had higher levels of serum IL-6 and total cholesterol as well as lower serum albumin and Kt/V values. The BDI correlated significantly with Kt/V values (r = -0.19; P < 0.05), levels of serum albumin (r = -0.28; P < 0.005) and serum IL-6 (r = 0.47; P < 0.001). Multivariate stepwise forward logistic regression analysis showed a direct correlation between BDI and IL-6 levels (P = 0.001; OR = 1.537) and between BDI and co-morbidities (P = 0.037; OR = 3.584). There was an inverse correlation between BDI and serum albumin levels (P = 0.006; OR = 0.145) and between BDI and age (P = 0.007; OR = 0.96). The rate of depression was significantly lower for the elderly patients (age >= 75 years) compared with those below 64 years of age. The percentage of personal monthly disposable income at or above Taiwan dollar (TWD) >10 000 was similar in patients aged >= 75 and those below 64 years old. Conclusions. Maintenance haemodialysis patients with symptoms of depression may have higher serum IL-6 and lower serum albumin levels. The prevalence of depression was lower in elderly patients at or above 75 years old, and no correlation was found with socio-economic status. Factors including co-morbid conditions, serum IL-6, albumin and age may help predict which patients may be predisposed to develop symptoms of depression.