Supplementary Material for: Oxidative Balance Score and the Risk of End-Stage Renal Disease and Cardiovascular Disease

Background: Oxidative balance score (OBS) is a
composite measure of oxidative stress-related exposures. The aim of this
study was to investigate the association between OBS, end-stage renal
disease (ESRD), and cardiovascular disease (CVD). Methods:
Using data from the Chronic Renal Insufficiency Cohort, we calculated
the main exposure OBS by summing up 12 apriori-defined pro- and
antioxidant factors obtained from the diet history questionnaire and
lifestyle assessment. We divided OBS into quartiles (Q1-Q4), with Q1
(predominance of pro-oxidants) as the reference. We analyzed OBS
quartiles as an ordinal variable. Crude and adjusted hazards ratios
(HRs) and 95% CIs were estimated using Cox proportional hazards models
for time to ESRD and CVD. Results: Compared to Q1, Q4
(high antioxidant) was associated with ESRD in the crude model (HR 1.35,
95% CI 1.08-1.69) and adjusting for age, sex, and race (HR 1.36, 95% CI
1.09-1.71) but not in the fully adjusted model (HR 1.12, 95% CI
0.84-1.51). HR of ESRD increased as the OBS quartiles increased in the
crude model (ptrend < 0.05) but not in the fully adjusted model (ptrend
= 0.30). Compared to Q1, Q4 was associated with CVD in the crude (HR
1.33, 95% CI 1.06-1.68) but not adjusted models. The HR of CVD increased
with an increase in OBS quartiles in the crude model (ptrend < 0.05). Conclusion:
The reverse association between OBS and progression to ESRD suggests
that perhaps the effect of oxidative balance-related exposure is
different in the setting of established chronic kidney disease.