IL-1β, IL-6, TNF-α and CRP in Elderly Patients with Depression or Alzheimer's disease: Systematic Review and Meta-Analysis

We carried out systematic review and meta-analysis to evaluate whether peripheral levels of proinflammatory markers including Interleukin-1 beta (IL-1 beta), Interleukin-6 (IL-6), Tumor Necrosis Factor-alpha (TNF-alpha) and C-Reactive Protein (CRP) are significantly higher in elderly with depression and Alzheimer's disease. We searched Pubmed, PsycINFO and Embase, and thirty-four relevant studies (2609 with Depression, 1645 with Alzheimer's disease and 14363 Controls) were included. Compared with controls, IL-1 beta (pooled standardized mean difference [SMD]: 0.642; 95% confidence interval [CI]: 0.078-1.206; significant heterogeneity: I-2 = 86.28%) and IL-6 (pooled SMD: 0.377; 95% CI: 0.156-0.598; significant heterogeneity: I-2 = 88.75%) were significantly elevated in depression. There was no difference in TNF-alpha (p = 0.351) and CRP (p = 0.05) between those with depression and controls. Compared with controls, IL-1 beta (pooled SMD: 1.37, 95% CI: 0.06-2.68, significant heterogeneity: I-2 = 96.01%) was significantly elevated in Alzheimer's disease. There were no differences in IL-6 (p = 0.138), TNF-alpha (p = 0.451) and CRP (p = 0.07) between elderly with Alzheimer's disease and controls. After Bonferroni adjustment, only IL-6 remained significantly higher in depression. Elderly with depression have higher IL-6 than controls, while those with Alzheimer's disease did not have higher peripheral inflammatory markers.