Non-linear associations of total and leisure-time physical activity with chronic kidney disease: Findings from NHANES.

Physical activity (PA) is a protective factor for many chronic diseases, but its association with chronic kidney disease (CKD) remains unclear. Using National Health and Nutrition Examination Survey (NHANES) data (2007-2016), this study examined the relationship between PA and CKD among participants aged 20 years or older who had valid data on both kidney function and PA. PA was assessed via the Global Physical Activity Questionnaire, which captured the frequency, duration, and intensity of occupation-activities, transportation-activities, and leisure-time-related activities. CKD was defined using estimated glomerular filtration rate (eGFR) calculated from serum creatinine and urinary albumin-to-creatinine ratio (UACR), based on KDIGO guidelines. Multivariable logistic regression revealed a significant inverse association between total PA and CKD risk (OR = 0.90; 95% CI, 0.84-0.96; P = 0.003), and leisure-time PA (LTPA) was also inversely associated with CKD (OR = 0.89; 95% CI, 0.82-0.96; P = 0.002), while occupation-related PA (OPA) and transportation-related PA (TPA) showed no significant associations. Subgroup and interaction analyses of total PA and LTPA across survey cycles, sex, age, race, educational level, FPIR, marital status, smoking status, drinking status, dietary supplements and protein, total fat, carbohydrate and energy from diet identified no significant effect modifiers. We further performed restricted cubic spline (RCS) analyses for both total PA and LTPA, which revealed significant non-linear inverse relationships with CKD risk (all P < 0.001 for non-linearity). In addition, mediation analyses suggested that the inverse association between total PA and CKD was partially mediated through BMI, diabetes, hypertension, and systemic inflammation.