What explains black-white differences in survival in idiopathic dilated cardiomyopathy? The Washington, DC, Dilated Cardiomyopathy Study.

We have found race to be an independent predictor of mortality in a preliminary analysis of data from an ongoing study of patients with idiopathic dilated cardiomyopathy. Our previous, analyses, however, were based on only 12 to 24 months of follow-up. In the present analysis, which is based on up to 5 years of follow-up, we extended our earlier observations and examined whether other socioeconomic factors account for the association with race. A total of 128 patients from five Washington, DC, area hospitals were included in the analysis. One hundred three (80.5%) of the patients were black and 25 (19.5%) were white. The black patients were less likely to have private health insurance, less educated on average, and more likely to have a household income < or = $15,000. No racial differences were found in cardiac medication usage, with the exception of beta blockers and antiarrhythmics. The cumulated survival among black patients at 12 and 60 months was 71.5% and 39.1%, respectively, compared with 92% and 31.4% among whites. Age, ventricular arrhythmias, and ejection fraction were significant predictors of survival in univariate analysis. The univariate association with black race was of borderline significance. In multivariable analysis using the proportional hazards model, age and ejection fraction were significant independent predictors of survival. The association with ventricular arrhythmias was of borderline significance. The association with black race, which was statistically nonsignificant, was diminished even further by adjustment for income and type of health insurance. Thus, the previously reported association with black race may be accounted for by socioeconomic factors related to access to health care.