Covariates

The NHANES release information about socio-demographic factors, health-related lifestyles, and health conditions through demographics, questionnaires, examination, and laboratory data. based on previous research, we included some of them as covariates related to CKD and grip

strength

8,18

. Socio-demographic factors included age (≥ 40 years), gender (male and female), race

(Mexican American, other Hispanic, non-Hispanic White, non-Hispanic Black, and other races), Family PIR reflected family income level, which was divided into three categories (≥4, 1–4, ≤1)

to reflect house income. The higher ratio indicated a better family financial situation. A special

diet was defined as a weight loss diet, low-fat diet, low salt diet, sugar-free diet, high-fibre diet, diabetic diet and weight gain diet. Rigorous work activity was a potential rigorous physical