Serum creatinine/cystatin C ratio is a predictor of all-cause mortality for older adults over 80 years.

Objective: Sarcopenia is a prevalent condition in the senior population and has been related to adverse outcomes. This study aimed to investigate the performance of the serum creatinine/cystatin C ratio (Cr/CysC) in predicting all-cause mortality in elders over 80 years.

Methods: A total of 486 older patients over 80 were enrolled in this study. Calf circumference (CC) and handgrip strength (HGS) were carried out for each patient. All the participants accepted serum creatinine and cystatin C test. The primary clinical outcome was all-cause mortality during an over-4-year follow-up.

Results: During an over 4-year follow-up, 200 participants died. The non-survivors had a significantly lower baseline Cr/CysC level than the survivors (62.6 ± 13.1 vs. 71.4 ± 14.5  < 0.001). The lowest Cr/CysC quartile group (Q1) had a significantly higher mortality rate than their counterparts (Q1 vs. Q2-4, 62.8% vs. 33.2%,  < 0.001). The Cr/CysC level was positively correlated with CC (R = 0.17,  < 0.001) and HGS (R = 0.19,  < 0.001). Moreover, survival curve was significantly worse in the lowest Cr/CysC quartile (Log-rank test χ = 21.09,  < 0.001). After adjustment for potential confounders, age (HR, 1.10; 95% CI, 1.06-1.14,  < 0.001), coronary heart disease (HR, 1.49; 95% CI, 1.01-2.21,  = 0.045), and lowest Cr/CysC (HR, 1.59; 95% CI, 1.12-2.24,  = 0.009) were independent factors of all-cause mortality during the over-4-year follow-up.

Conclusion: Cr/CysC, also known as Sarcopenia Index, could be used as a predictor of all-cause mortality in older adults over 80 years.