Exploring the potential of salivary and blood immune biomarkers to elucidate physical frailty in institutionalized older women

Identification of older populations at increased risk of physical frailty using biochemical approaches could improve screening accuracy. The aim of this study was to study the relationship between immune markers and independent components of physical frailty in institutionalized older women. A sample of 358 institutionalized-dwelling women, aged 75 years and older, were assessed for biosocial factors and general health status, pro and anti-inflammatory cytokines, sex steroid hormones, salivary anti-microbial proteins, blood cells counts and the five Fried's physical frailty components that allowed for classification of the sample into frail, prefrailty and not-frail subgroups. Results showed that cytokines IL-6, IL-10, IL-1β, TNF-α, and the TNF-α/IL-10 ratio, mean corpuscular haemoglobin, salivary cortisol and α-amylase were all associated with frailty. Weakness and Exhaustion were the frailty components that were most strongly associated with these biomarkers. Salivary α-amylase was the biomarker that best explained frailty, as it was associated with all five components of physical frailty, and could be used as a potential screening tool. Future research needs to investigate the causal-effect association between salivary innate immune makers, susceptibility to infection and frailty.