Relationship of creatinine cystatin C ratio with muscle mass and grip strength in memory clinic outpatients

Objectives: The purpose of this study was to examine the relationship of the serum creatinine/cystatin C ratio (CCR) with hand grip strength (HGS), total body muscle mass, trunk muscle mass, and skeletal muscle mass index (SMI) in patients attending a memory clinic. Design: This cross-sectional study enrolled outpatients of a memory clinic in Japan from October 2010 to July 2017. Setting and participants: We enrolled 1945 participants aged 60 years or older with measured skeletal muscle mass, HGS, and serum creatinine and serum cystatin C levels. Measures: Linear multiple regression analysis was performed for men and women using total body muscle mass, trunk muscle mass, and SMI as objective variables. The exposure variables were selected from previous reports if they were strongly linked to muscle mass. Total body muscle mass and trunk muscle mass were corrected by dividing by body weight. Multiple regression analysis was also conducted for men and women using HGS as an objective variable. Because cognitive function and HGS are strongly related, we also conducted sensitivity analysis by excluding participants with a Mini-Mental State Examination score < 24 to alleviate any concern that we did not fully adjust for the effect of cognitive dysfunction. Results: In men, CCR was significantly associated with total body muscle mass, trunk muscle mass, and SMI (P = 0.013, P = 0.008, and P < 0.001, respectively). In women, CCR was significantly associated with total body muscle mass and trunk muscle mass (P = 0.013 and P < 0.001, respectively), but not with SMI (P = 0.932). On the other hand, CCR was significantly associated with grip strength in both men and women (P < 0.001 and P < 0.001, respectively). Conclusions: CCR was associated with both muscle mass and muscle strength. This study suggests that CCR is a useful marker not only for muscle mass but also for muscle strength.