A link between systemic low-grade inflammation and frailty in older adults: clinical evidence from a nationwide population-based study

Background/Aims: Despite the possible role of systemic low-grade inflammation on frailty, the majority of previous studies have focused solely on the phenotypic frailty with limited participant numbers, thereby weakening the evidence supporting the notion that circulating C-reactive protein (CRP) could be a potential frailty biomarker. Methods: This study is a nationally representative, population-based, cross-sectional analysis from the Korea National Health and Nutrition Examination Survey, involving 5,359 participants aged 65 and older. We generated a deficit accumulation frailty index (FI) based on 38 items, encompassing physical, cognitive, psychological, and social status. Frailty was classified as non-frail (FI <= 0.15), pre-frail (0.15 < FI <= 0.25), or frail (FI > 0.25). Serum high-sensitivity CRP (hsCRP) levels were measured by immunoturbidometric method. Results: After adjusting for confounders including age, sex, income, education, smoking, hypertension, diabetes, dyslipidemia, stroke, cardiovascular diseases, and body mass index, serum hsCRP levels were 29.4% higher in frail participants compared to their non-frail counterparts (p p = 0.001). Additionally, circulating hsCRP concentrations positively correlated with the FI (p p = 0.003), and the odds ratio for frailty per standard deviation increase in serum hsCRP was 1.18 (p p = 0.001). Moreover, older adults in the highest hsCRP quartile exhibited a significant higher FI with a 1.59-fold increased odds ratio for frailty than those in the lowest quartile (p p = 0.002 and 0.001, respectively). Conclusions: These findings validate the impact of age-related systemic low-grade inflammation on frailty and support the utility of serum hsCRP as a potential biomarker for detecting frailty in older adults.