Patterns of comorbidity and mortality risk in blacks and whites

Comorbidity, the co-existence of multiple chronic conditions in a single individual, has been shown to modify the prognosis of disease states. To estimate disease burdens within and among racial subpopulations of the United States, we examined cross-sectional patterns of comorbidity and their impact on survival using data from the NHANES-1 Epidemiologic Follow-up Study (NHEFS). We considered the occurrence of four cardiovascular conditions: stroke, coronary heart disease, hypertension and diabetes. We summarize the joint occurrence of these four conditions using these different methodologies: the number of conditions occurring in each individual and two summaries that weight the conditions according to their prognostic significance. Using all three methodologies, we found an excess burden of chronic disease in black women as compared with white women. Black men had an excess burden compared to white men for the first two methodologies. However, when we model the relationship of the joint occurrence of the conditions to subsequent mortality, black men and white men are seen to have a similar burden. This similarity of black and white men is due to an interaction between race and prevalent stroke in men that we hypothesize may be due to the small number of black men available for study. Given the apparent conditioning effect of co-existing diseases, it is evident that estimation of disease burdens among groups that differ in terms of health status, in particular among U.S. blacks and whites, requires accounting for the occurrence of multiple chronic diseases. Using either the number of conditions or the prognosis weighted summary, we demonstrated a higher burden of the conditions considered in blacks that in whites in a sample of the U.S. population.