Declining kidney function and frailty progression: a 7-year cohort study of Chinese middle-aged and older adults

BACKGROUND: This study aimed to investigate the association between baseline kidney function and frailty trajectories in middle-aged and older adults. METHODS: ) and categorized as normal (≥90), mildly reduced (60-89) and moderately-to-severely reduced (<60 ml/min/1.73m²). Frailty was assessed using a 30‑item frailty index (0-100 scale). Linear mixed-effects models with random intercepts were used to examine the effects of baseline kidney function and its interaction with time on frailty index trajectories. RESULTS: At baseline, the mean frailty index was higher in participants with mildly (β=2.28, 95% CI: 1.63-2.94) and moderately-to-severely (β=3.70, 95% CI: 2.41-4.99) reduced kidney function compared to normal kidney function, where β represents the adjusted difference in frailty index relative to the reference group. Frailty index increased over time in all groups; in participants with normal kidney function, it rose by 0.83 points per year (95% CI: 0.77-0.90). The annual increase was 0.26 points greater (95% CI: 0.18-0.35) in the mildly reduced and 0.70 points greater (95% CI: 0.54-0.87) in the moderately-to-severely reduced group. Over approximately 7 years, predicted mean frailty index increased from 15.1 to 20.9, 17.4 to 25.0, and 18.8 to 29.5 in the normal, mildly reduced and moderately-to-severely reduced groups, respectively. CONCLUSIONS: Middle-aged and older adults with lower kidney function exhibited higher frailty index levels at baseline and faster frailty progression over time.