Mediators of the Association between Low Socioeconomic Status and Chronic Kidney Disease in the United States

Vart, Priya

INTRODUCTION: Substantial socioeconomic disparities exist in the prevalence of chronic kidney disease (CKD). Reducing such disparities requires identification of potentially modifiable factors linking low socioeconomic status (SES) to CKD, and estimation of the extent to which correction for these factors may reduce SES disparities. Therefore, we formally investigated the presence and magnitude of mediation in the SES-CKD association.

METHODS: In this cross-sectional study, data from 9,823 participants in the 2007-2008 and 2009-2010 National Health and Nutritional Examination Surveys (NHANES) was examined. SES was defined using the poverty income ratio (PIR). The primary outcome was CKD, defined as an estimated glomerular filtration rate <60 ml/min/1.73m² (CKD-Epidemiology Collaboration Equation) and/or urinary albumin-creatinine ratio ≥30mg/g. In mediation analyses we tested the contribution of health-related behaviors (smoking, alcohol intake, diet, physical activity and sedentary time), comorbid conditions (diabetes, hypertension, obesity, abdominal obesity and hypercholesterolemia) and health care access (health insurance and routine visits for health care) to this association.

RESULTS: Low SES was associated with CKD [Odds Ratio (OR) 1.64 (95% confidence interval 1.42 - 1.89)] for low SES versus high SES] when adjusted for age, gender and race. The addition of mediating health-related behaviors, comorbid conditions and health care access to this model resulted in 31.1%, 24.7% and 13.7% attenuation of the OR, respectively. Simultaneous addition of health-related behaviors, comorbid conditions and health care access led to 66.9% attenuation of the low SES-CKD association. In race/ethnicity specific analyses, the identified mediators attenuated 44.5%, 74.8%, 39.9% and 41.8% of the low SES-CKD association in non-Hispanic whites, non-Hispanic blacks, Mexican-Americans and others, respectively.

CONCLUSIONS: Potentially modifiable factors like health-related behaviors, comorbid conditions and health care access contribute substantially to the association between low SES and CKD in the US, especially among non-Hispanic blacks. Improvement of these factors could mitigate socioeconomic disparities in CKD.