Association Between Serum Ferritin Levels and Frailty Risk in Community-Dwelling Older Adults: A Nationwide Population-Based Study

Background Ferritin is a key iron storage protein and a marker of iron metabolism, linked to various health outcomes beyond hematologic conditions. This study examined the association between serum ferritin levels and the frailty index (FI), a comprehensive measure of health status and biological aging, in community-dwelling older adults. Methods We performed a population-based, cross-sectional analysis using data on 6,722 participants aged 65 years and older from the Korea National Health and Nutrition Examination Survey. A 36-item deficit accumulation FI was developed, encompassing physical, cognitive, psychological, and social domains. Participants were classified as non-frail (FI ≤ 0.15), pre-frail (0.15 < FI ≤ 0.25), or frail (FI > 0.25). Serum ferritin levels were measured using an immunoradiometric assay, and individuals were categorized into sex-specific quartiles. Results In both women and men, the FI exhibited a non-linear pattern across ferritin quartiles, with the lowest FI observed in the third quartile (Q3). Among women, FI was significantly higher in both the lowest (Q1) and highest (Q4) quartiles compared to Q3 ( P  < 0.001 and 0.001, respectively). Consistently, women in Q1 and Q4 had significantly higher odds of frailty compared to Q3, at 2.03 and 1.35 times, respectively ( P <  0.001 and 0.049, respectively). Although a similar trend was observed in men, the associations were not statistically significant. Conclusions Both low and high serum ferritin concentrations were associated with increased frailty risk, particularly in women. These findings suggest that serum ferritin may potentially serve as a predictive biomarker for frailty in older adults.