Educational level and risk of chronic kidney disease: Longitudinal data from the PREVEND study

Abstract

Background. The longitudinal association between low education and chronic kidney disease (CKD) and its underlying mechanisms is poorly characterized. We therefore examined the association of low education with incident CKD and change in kidney function, and explored potential mediators of this association. Methods. We analysed data on 6078 participants from the community-based Prevention of Renal and Vascular End-stage Disease study. Educational level was categorized into low, medium and high (secondary, secondary/equivalent, secondary schooling, respectively). Kidney function was assessed by estimating glomerular filtration rate (eGFR) by serum creatinine and cystatin C at five examinations during 11 years of follow-up. Incident CKD was defined as newonset eGFR60 mL/min/1.73 m2 and/or urinary albumin30 mg/24 h in those free of CKD at baseline. We estimated main effects with Cox regression and linear mixed models. In exploratory causalmediation analyses, we examinedmediation by several potential risk factors. Results. Incident CKD was observed in 861 (17%) participants. Lower education was associated with higher rates of incident CKD [low versus high education; hazard ratio (HR) (95% CI) 1.25 (1.05-1.48), Ptrend 0.009] and accelerated eGFR decline [B (95% CI) 0.15 (0.21 to 0.09) mL/min/1.73 m2/year, Ptrend 0.001]. The association between education and incident CKD was mediated by smoking, potassium excretion, body mass index (BMI), waist-To-hip ratio (WHR) and hypertension. Analysis on annual eGFR change in addition suggested mediation by magnesiumexcretion, protein intake and diabetes. Conclusions. In the general population, we observed an inverse association of educational level with CKD. Diabetes and the modifiable risk factors smoking, poor diet, BMI, WHR and hypertension are suggested to underlie this association. These findings provide support for targeted preventive policies to reduce socioeconomic disparities in kidney disease.