The Effects of Urbanization on Chronic Kidney Disease and Renal Function Decline: Findings from a Nation-Wide Longitudinal Study

Chronic kidney disease (CKD) has become a global public health concern, especially in developing countries. Although previous studies have suggested a link between urbanization and CKD, the existing evidence remains limited and inconsistent. We selected a sub-cohort of 5298 participants from the China Health and Retirement Longitudinal Study (CHARLS). All participants had normal renal function at baseline (2011) and were followed up in 2015, with renal biomarkers measured twice. Urbanization was assessed at the city level using the average nighttime light index (ANLI), derived from calibrated long-term satellite remote sensing data. Logistic regression models were used to examine the association between urbanization and CKD. Our results showed that a 0.1-unit increase in ANLI was associated with a 7.3% increase in the relative risk of CKD in the fully adjusted model (OR: 1.073, 95% CI: 1.045, 1.101). Subgroup analyses indicated that females (OR: 1.106, 95% CI: 1.068, 1.145) and urban residents (OR: 1.101, 95% CI: 1.060, 1.143) were at higher risk. We also found the synergistic amplification effects of heavier air pollution (PM_2.5 and NO₂) and elevated temperatures on this association. Our findings provide robust evidence of a positive association between urbanization and CKD among middle-aged and elderly adults in China. More scientific and specific health investment is needed with urbanization process simultaneously.