Comparative associations of non-alcoholic fatty liver disease and metabolic dysfunction-associated steatotic liver disease with risk of incident chronic kidney disease: a cohort study.

Background: We examined the comparative associations between non-alcoholic fatty liver disease (NAFLD) and metabolic dysfunction-associated steatotic liver disease (MASLD) definitions with risk of developing chronic kidney disease (CKD) and abnormal albuminuria. Methods: We conducted a cohort study of 214,145 Korean adults with normal kidney function at baseline who underwent liver ultrasonography. Participants were further subdivided into no steatotic liver disease (no-SLD), NAFLD-only, MASLD-only, both NAFLD and MASLD, and SLD not categorized as NAFLD or MASLD groups. Cox proportional hazards models were used to analyze the risk of incident CKD and albuminuria. Results: Compared with either the no-NAFLD or no-MASLD groups, the NAFLD and MASLD groups were associated with a higher risk of incident CKD (NAFLD: adjusted hazard ratio (HR), 1.18 [95% CI, 1.01-1.38]; MASLD: adjusted HR, 1.21 [95% CI, 1.04-1.39]). Among the five subgroups, both NAFLD and MASLD group had the strongest association with risk of incident CKD (adjusted HR, 1.21 [95% CI, 1.04-1.42]). The MASLD-only group had the strongest association with incident abnormal albuminuria, with an adjusted HR comparable to that of the both NAFLD and MASLD group (adjusted HR 1.96 [95% CI, 1.44-2.67] for the MASLD-only, and adjusted HR 1.98 [95% CI, 1.58-2.49] for the both NAFLD and MASLD group versus the no-SLD group). The NAFLD-only group was not independently associated with risk of CKD or abnormal albuminuria. Conclusions: These findings suggest that MASLD definition identifies individuals at high risk of developing incident CKD or abnormal albuminuria better than NAFLD definition.