Geographic disparities in kidney function decline: a matched cohort analysis of urban and rural populations in Korea

Background: Previous studies have shown differing chronic kidney disease (CKD) prevalence between rural and urban populations; data on longitudinal renal function decline remain limited.We compared kidney function deterioration rates between rural and urban residents in Korea.Methods: We analyzed data from the Korean Genome and Epidemiology Study (KoGES), including 60,487 urban and 14,776 rural participants.Individuals with baseline estimated glomerular filtration rate (eGFR) 60 mL/min/1.73m and proteinuria <1+ were included.Using multiple imputation and propensity score matching (1:1 by age, sex, baseline eGFR, and proteinuria), we compared the risk of rapid progression-defined as an annual eGFR decline >5 mL/min/1.73m-between urban and rural residents.Logistic regression and mediation analyses were conducted across five imputed matched datasets.Results: Among 14,336 matched urban and rural participants, rapid progression occurred in 1.9% and 9.1%, respectively.Rural residency was independently associated with significantly higher odds of rapid progression, with an adjusted odds ratio (OR) of 5.42 (95% confidence interval, 4.61-6.37) in the fully adjusted model.Mediation analysis identified serum albumin, educational attainment, and dietary protein intake as key mediators (total indirect effect OR, 1.12; p < 0.001), although a significant direct effect of rural residence remained.Conclusion: Rural residency was associated with a substantially elevated risk of rapid progression, mediated in part by nutritional and socioeconomic disparities.These findings highlight the need for targeted strategies to mitigate kidney health inequities in underserved regions.