Association of MASLD with chronic kidney disease according to metabolic profiles and fibrosis severity: a KNHANES analysis.

Background: Metabolic dysfunction-associated steatotic liver disease (MASLD) is increasingly recognized as a multisystem metabolic disorder with extrahepatic manifestations, including chronic kidney disease (CKD). However, population-level evidence on the renal impact of metabolic heterogeneity and fibrosis severity in MASLD remains limited. We aimed to evaluate the association between MASLD and prevalent CKD and to examine the contributions of metabolic components and liver fibrosis severity. Methods: We analyzed 17,229 adults (≥19 years) from the Korea National Health and Nutrition Examination Survey (KNHANES) 2011-2014. MASLD was defined as hepatic steatosis (hepatic steatosis index ≥36) with at least one cardiometabolic risk factor. CKD was defined as estimated glomerular filtration rate <60 mL/min/1.73 m² or urine albumin-to-creatinine ratio ≥30 mg/g. Survey-weighted logistic regression models estimated odds ratios (ORs) for CKD. Additive interaction between hypertension and diabetes was quantified using relative excess risk due to interaction (RERI) and attributable proportion (AP). Liver fibrosis severity was assessed using the log-transformed Fibrosis-4 index and restricted cubic spline analyses. Results: MASLD was associated with CKD (adjusted OR, 2.47; 95% CI, 1.76-3.47; p<0.001). Within MASLD, hypertension and diabetes were consistently associated with CKD. While point estimates suggested a positive additive interaction between these factors (RERI = 0.60; AP = 0.10), it did not reach statistical significance. Increased fibrosis severity showed a graded association with CKD, particularly among middle-aged adults. Conclusion: MASLD was associated with prevalent CKD. The association with prevalent CKD within MASLD varied according to metabolic profiles and fibrosis severity, highlighting the importance of risk stratification and integrated liver-kidney management.