Creatinine-to-cystatin C ratio as a marker of skeletal muscle mass in older adults: J-SHIPP study

Abstract

Background: Sarcopenia increases mortality risk in older adults. Loss of skeletal muscle mass is a cardinal feature of sarcopenia. The creatinine-to-cystatin C ratio (CCR) has been suggested as a marker of muscle mass. The present study investigated the usefulness of CCR in discriminating the risk of low muscle mass and weak muscle strength in an elderly population.

Methods: The present cross-sectional study included 1,329 apparently healthy community residents aged 60 years or older. The cross-sectional area (CSA) of muscle in the mid-thigh was measured using computed tomography. Clinical data recorded at routine medical check-ups were obtained from each participant's medical record.

Results: Mean muscle CSA was 109 ± 24 cm². CCR by quartiles according to sex was strongly associated with muscle CSA (Q1: 104 ± 22, Q2: 108 ± 24, Q3: 110 ± 23, and Q4: 114 ± 25 cm², F = 10.38, P < 0.001). This association was independent of major covariates (Q1: reference, Q2: β = 0.06, P < 0.001, Q3: β = 0.10, P < 0.001, and Q4: β = 0.17, P < 0.001) even in a sex-separated analysis. Although creatinine alone was independently associated with muscle CSA (F = 5.81, P < 0.001), the association was weaker than that of CCR, particularly in the individuals with renal functional decline. Also, CCR was associated with grip strength independently of muscle CSA.

Conclusion: CCR was a simple marker of low muscle mass and weak muscle strength in older community-dwelling adults.

Keywords: Creatinine; Cystatin C; General population; Sarcopenia; Skeletal muscle.