Race and end-stage renal disease. Socioeconomic status and access to health care as mediating factors.

OBJECTIVE: To examine whether lower socioeconomic status and limited access to health care explain the racial inequities in the incidence of end-stage renal disease (ESRD), and whether these factors are independently associated with ESRD.
METHODS: This case-control study compared 716 patients with ESRD with 361 population controls of the same age, 20 to 64 years old, from Maryland, Virginia, West Virginia, and Washington, DC. Race, indicators of socioeconomic status (household annual income, years of education), and indicators of access to health care (health insurance status, number of missing teeth, usual source of care, use of preventive services) were assessed via a telephone interview.
RESULTS: Independent risk factors for ESRD included non-white race (odds ratio for blacks, 5.5; 95% confidence interval, 3.8 to 8.0; odds ratio for other nonwhites, 3.5; 95% confidence interval, 1.2 to 10.0), categories of income (odds ratio gradient, 1.0 to 4.5; 95% confidence interval, 2.6 to 7.8), receipt of Medicaid benefits (odds ratio, 3.5; 95% confidence interval, 1.5 to 8.4), and number of missing teeth (odds ratio gradient, 1.0 to 2.2; 95% confidence interval, 1.2 to 4.1). Adjustment for socioeconomic variables reduced the odds ratio for blacks only partially, from 8.1 to 5.5. The proportions of ESRD incidence that could be attributed to each risk factor were 46% for minority race, 53% for income categories, and 33% for missing teeth.
CONCLUSIONS: Low socioeconomic status and limited access to health care were strong risk factors for kidney failure, but they explained only part of the excess of ESRD in blacks. Racial and social factors account for a large part of ESRD incidence. The mechanisms of these associations should be targeted by further research.