Level of IL-6, TNF, and IL-1β and age-related diseases: a systematic review and meta-analysis

Introduction: Chronic low-grade inflammation is an important aspect of morbidity and mortality in older adults. The level of circulating pro-inflammatory cytokines (interleukin (IL)-6, tumor necrosis factor (TNF) or IL-1β) is a risk factor in cardiovascular and neurodegenerative diseases and is also associated with sarcopenia and frailties. The objective of this study was to assess each cytokine: IL-6, TNF, and IL-1β separately in the elderly with comorbidities against controls without diseases according to the data published in the available literature.

Methods: The electronic bibliographic PubMed database was systematically searched to select all the relevant studies published up to July 2023. The total number of the subjects involved in the meta-analysis included patients with diseases (n=8154) and controls (n=33967).

Results: The overall concentration of IL-6 was found to be higher in patients with diseases compared to controls and the difference was statistically significant, with a p-value of <0.001 (SMD, 0.16; 95% CI, 0.12-0.19). The heterogeneity was considerable with Q = 109.97 (P <0.0001) and I² = 79.2%. The potential diagnostic usefulness of IL-6 was confirmed by odds ratio (OR) analysis (OR: 1.03, 95% CI (1.01; 1.05), p=0.0029). The concentration of both TNF and IL-1β was elevated in the control group compared to patients and amounted to SMD -0.03; 95% CI, -0.09-0.02, p-value 0.533 and SMD-0.29; 95% CI, -0.47- -0.12; p = 0.001, respectively. For TNF, however, the difference was statistically insignificant.

Discussion: IL-6, unlike TNF and IL-1β, could be a useful and convenient marker of peripheral inflammation in older adults with various comorbidities.