Interleukin 6, soluble tumor necrosis factor receptor I and red blood cell distribution width as biological markers of functional dependence in an elderly population: A translational approach

► High IL-6 and sTNF-RI levels are associated with poor functional status. ► High RDW level is associated with poor functional status. ► Up-regulation of inflammatory mediators is associated with functional dependence. ► The assessment of IL-6, sTNF-RI and RDW may represent a useful screening test. ► IL-6, sTNF-RI and RDW may indicate potential intervention targets. In the present investigation we have analyzed the association between functional dependence and inflammatory biomarkers using the Barthel Index (BI) and the Katz Index (KI). This analysis may contribute to translational medicine by incorporating the clinical and laboratory data to better understand the relationship between chronic inflammation and functional dependence in the elderly population. The ultimate goal of this study was to identify possible useful biomarkers of functional dependence in the elderly. Participants in this study consisted of 120 older subjects (90 women and 30 men; range 68–105years) who were selected from the Santa Teresa nursing home (Oviedo, Spain). We studied functional status using the following tools to diagnose the functional dependence by clinicians: BI and KI for activities of daily living. We analyzed morbidity, sociodemographic characteristics and a panel of inflammatory and inflammatory-related markers. In linear regression models adjusted by age, sex, anti-inflammatory drug use and morbid conditions high levels of interleukin 6 (IL-6) and soluble TNF receptor-I (sTNF-RI) were associated with functional dependence as measured using BI and KI. Elevated levels of red blood cell distribution width (RDW) were also associated with functional dependence measured using the KI after adjusting for the same potential confounders. The current results suggest that high IL-6, sTNF-RI and RDW levels are associated with the functional dependence in the elderly population. The results are consistent with the presumed underlying biological mechanism, in which the up-regulation of inflammatory mediators is associated with functional dependence in elderly subjects.