Impact of educational level on incident chronic kidney disease during 13 years of follow-up: a prospective cohort study

Objectives: To examine the association between educational level and chronic kidney disease (CKD) among the Iranian population. Study design: This is a prospective cohort study conducted in the framework of the Tehran Lipid and Glucose Study. Methods: A total of 8173 Iranians (men = 3659) aged =20 years were included in the study. CKD was defined as estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m(2). The association between educational status and CKD was explored using multivariate Cox proportional regression analyses, adjusted for age, gender, current smoking, marital status, body mass index, waist circumference, baseline eGFR, diabetes, hypertension, physical activity, history of cardiovascular diseases and dyslipidaemia. Results: During a median follow-up of 13.14 years, 2609 cases of incident CKD were identified; the corresponding incidence rate was 26.35 (range 25.39-27.34) per 1000 person-years. Compared to low educational level, middle and high educational levels showed lower risks for incident CKD in the crude model [hazard ratio (HR) 0.37 (95% confidence interval {CI} 0.34-0.40) and HR 0.40 (95% CI 0.35-0.45), respectively]; however, these HRs changed direction after further adjustment for age and gender [HR 1.26 (95% CI 1.14-1.39) and HR 1.40 (95% CI 1.22-1.61), respectively]. The increased risk of incident CKD for those at higher educational levels remained significant in the fully adjusted model. In addition, results from the gender stratified analyses were in the same direction as those found among the whole study population (P-value for interaction of gender and education >0.8). Conclusions: Higher educational levels were associated with incident CKD during more than a decade of follow-up; this finding may be attributed to unhealthy lifestyle behaviours among this population group. (C) 2021 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.