Supplementary Material for: Oxidative Balance Score and Chronic Kidney Disease

<br><strong><em>Background:</em></strong> The oxidative balance score (OBS) is a composite estimate of the overall pro- and antioxidant exposure status in an individual. The aim of this study was to determine the association between OBS and renal disease. <b><i>Methods:</i></b> Using the Reasons for Geographic and Racial Differences in Stroke cohort study, OBS was calculated by combining 13 a priori-defined pro- and antioxidant factors by using baseline dietary and lifestyle assessment. OBS was divided into quartiles (Q1-Q4) with the lowest quartile, Q1 (predominance of pro-oxidants), as the reference. Multivariable logistic regression and Cox proportional hazards models were used to estimate adjusted ORs for albuminuria defined as urine albumin/creatinine ratio (ACR) >30 mg/g, macroalbuminuria defined as ACR >300 mg/g and chronic kidney disease (CKD) defined as estimated glomerular filtration rate <60 ml/min/1.73 m<sup>2</sup> according to the Chronic Kidney Disease Epidemiology Collaboration and hazards ratios for end-stage renal disease (ESRD), respectively. <b><i>Results:</i></b> Of the 19,461 participants analyzed, 12.9% had albuminuria and 10.1% had CKD at baseline; over a median follow-up of 3.5 years (range 2.14-4.32 years), 0.46% developed ESRD. Higher OBS quartiles were associated with lower prevalence of CKD (OR vs. Q1: Q2 = 0.93 [95% CI 0.80-1.08]; Q3 = 0.90 [95% CI 0.77-1.04] and Q4 = 0.79 [95% CI 0.67-0.92], p for trend <0.01). The associations between OBS and albuminuria (p for trend 0.31) and incident ESRD (p for trend 0.56) were not significant in the fully adjusted models. <b><i>Conclusions:</i></b> These findings suggest that higher OBS is associated with lower prevalence of CKD. Lack of association with ESRD incidence in the multivariable analyses indicates that temporal relation between OBS and renal damage remains unclear.