Impact of Educational Attainment on Health Outcomes in Moderate to Severe CKD

Abstract

Background: The inverse association between educational attainment and mortality is well established, but its relevance to vascular events and renal progression in a population with chronic kidney disease (CKD) is less clear. This study aims to determine the association between highest educational attainment and risk of vascular events, cause-specific mortality, and CKD progression.

Study design: Prospective epidemiologic analysis among participants in the Study of Heart and Renal Protection (SHARP), a randomized controlled trial.

Setting & participants: 9,270 adults with moderate to severe CKD (6,245 not receiving dialysis at baseline) and no history of myocardial infarction or coronary revascularization recruited in Europe, North America, Asia, Australia, and New Zealand.

Predictor: Highest educational attainment measured at study entry using 6 levels that ranged from "no formal education" to "tertiary education."

Outcomes: Any vascular event (any fatal or nonfatal cardiac, cerebrovascular, or peripheral vascular event), cause-specific mortality, and CKD progression during 4.9 years' median follow-up.

Results: There was a significant trend (P<0.001) toward increased vascular risk with decreasing levels of education. Participants with no formal education were at a 46% higher risk of vascular events (relative risk [RR], 1.46; 95% CI, 1.14-1.86) compared with participants with tertiary education. The trend for mortality across education levels was also significant (P<0.001): all-cause mortality was twice as high among those with no formal education compared with tertiary-educated individuals (RR, 2.05; 95% CI, 1.62-2.58), and significant increases were seen for both vascular (RR, 1.84; 95% CI, 1.21-2.81) and nonvascular (RR, 2.15; 95% CI, 1.60-2.89) deaths. Lifestyle factors and prior disease explain most of the excess mortality risk. Among 6,245 participants not receiving dialysis at baseline, education level was not significantly associated with progression to end-stage renal disease or doubling of creatinine level (P for trend = 0.4).

Limitations: No data for employment or health insurance coverage.

Conclusions: Lower educational attainment is associated with increased risk of adverse health outcomes in individuals with CKD.

Trial registration: ClinicalTrials.gov NCT00125593.

Keywords: Chronic kidney failure; Study of Heart and Renal Protection (SHARP); chronic kidney disease (CKD); disease progression; education; educational attainment; end-stage renal disease (ESRD); health behavior; inequalities; mortality; renal dialysis; risk factor; socioeconomic factors; vascular event.

Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Relevance of highest education level attained to 2,317 vascular events (atherosclerotic and nonatherosclerotic). (A) Total effect: Cox proportional hazards model stratified by country and adjusted for age, sex, black ethnicity, and study treatment assignment. Test for trend χ2 = 16.12; P < 0.001. (B) Residual effect: Cox proportional hazards model stratified by country and adjusted for age, sex, black ethnicity, smoking, alcohol use, body mass index, chronic kidney disease stage, prior vascular disease, diabetes, renal diagnosis, systolic and diastolic blood pressure, albumin level, urinary albumin-creatinine ratio, hemoglobin level, phosphate level, high-density lipoprotein cholesterol level, and total cholesterol level. The size of the square representing a relative risk is proportional to its inverse variance; error bars represent 95% confidence intervals (CIs). Tests for trend in the models were evaluated after excluding participants with unrecorded education. Test for trend χ2 = 0.81; P = 0.4.

Figure 2

Relevance of highest education level attained to vascular, nonvascular, and overall mortality. (A) Total effects: Cox proportional hazards models stratified by country and adjusted for age, sex, black ethnicity, and study treatment assignment. Tests for trend: χ2 = 14.23; P < 0.001 for vascular deaths; χ2 = 29.42; P < 0.001 for nonvascular deaths; χ2 = 51.52; P < 0.001 for all deaths. (B) Residual effects: Cox proportional hazards models stratified by country and adjusted for age, sex, black ethnicity, study treatment assignment, smoking, alcohol use, body mass index, chronic kidney disease stage, prior vascular disease, diabetes, renal diagnosis, systolic and diastolic blood pressure, albumin level, urinary albumin-creatinine ratio, hemoglobin level, phosphate level, high-density lipoprotein cholesterol level, and total cholesterol level. The size of a square representing a relative risk is proportional to its inverse variance; error bars represent 95% confidence intervals (CIs). Tests for trend in all models were evaluated after excluding participants with unrecorded education. Tests for trend: χ2 = 2.76; P = 0.1 for vascular deaths; χ2 = 9.18; P = 0.003 for nonvascular deaths; χ2 = 15.09; P < 0.001 for all deaths.

Figure 3

Relevance of highest education level attained among 6,245 participants not on dialysis therapy at randomization to progression to end-stage renal disease or doubling of creatinine level. Participants with end point, n = 2,446. Test for trend, Wald χ2 = 0.71; P = 0.4. Cox proportional hazards model stratified by country and adjusted for age, sex, black ethnicity, and study treatment assignment. The size of the square representing a relative risk is proportional to its inverse variance; error bars represent 95% confidence intervals (CIs). Tests for trend in all models were evaluated after excluding participants with unrecorded education.