Associação entre creatinina, ácido úrico, ureia e suas razões com a cistatina c ou creatinina e força muscular em adultos com 50 anos ou mais: NHANES 1999-2002

Abstract

Introduction: The decline in muscle strength is associated with an increased risk of adverse clinical outcomes, such as falls, fractures, and higher mortality rates. In this context, practical and accessible strategies aimed at identifying the risk of low muscle strength in older adults are important. Some studies have investigated the use of specific biochemical parameters and their respective ratios in relation to muscle strength. However, it remains unclear which of these parameters or ratios are most strongly associated with muscle strength. Aim: The aim of this study was to evaluate whether, in addition to the creatinine-to-cystatin C ratio, creatinine, uric acid, urea, and their respective ratios with cystatin C are associated with muscle strength in older adults. Methods: A cross-sectional study was conducted involving 2215 participants aged between 50 and 85 years from a subsample of the National Health and Nutrition Examination Survey (NHANES) 1999–2000 and 2001–2002. Biochemical analyses included uric acid (colorimetric method), creatinine (Jaffe rate method), urea (enzymatic conductivity rate method), and cystatin C (immunoassay on the Siemens Dimension Vista 1500 analyzer). Muscle strength was assessed using a kinetic communicator isokinetic dynamometer. Dietary intake assessment was conducted by an interviewer using 24-h recalls. Linear regression analyses were conducted to examine the associations between muscle strength and creatinine, uric acid, urea, and their respective ratios with cystatin C, adjusting for potential confounding factors. Results: The creatinine-to-cystatin C ratio demonstrated a strong positive association with muscle strength (β = 86.6 (64.0; 109.1) p=< 0.001). Similarly, uric acid and the uric acid- to-cystatin C ratio were also positively associated (β = 4.0 (0.7; 7.2) p=<0.017); (β = 6.3 (3.2; 9.65) p=< 0.001). In contrast, cystatin C and the urea-to-creatinine ratio showed inverse associations with muscle strength (β = -1.5 (-2.4; -0.6) p=0.001). Conclusion: The creatinine- to-cystatin C ratio had the strongest association with muscle strength compared to the other biochemical ratios analyzed, while uric acid alone may be sufficient for assessing muscle strength, without the need for its ratio with cystatin C.