The burden of disease associated with being African-American in the United States and the contribution of socio-economic status

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Abstract

The burden of disease associated with being African-American in the US, and the contribution of socio-economic status (SES) to that burden have not been quantified. We derived burden of disease estimates for African-Americans and whites by age group, with and without adjustment for SES (income and education). We used (1) EQ-5D Index scores from the 2000 US Medical Expenditure Panel Survey to derive quality-adjusted life year (QALY) compatible estimates of health-related quality of life (HRQL); (2) 1990–1992 US National Health Interview Survey data linked to National Death Index data through 1995 to derive mortality risks; and (3) 2000 US mortality data from the National Center for Health Statistics to derive current mortality estimates for the US population. We found that relative to whites, African-Americans suffer 67,000 more deaths annually, resulting in 2.2 million years of life lost, and 1.1 million years after SES adjustment. Total QALYs lost (HRQL and mortality) dropped from 2.3 million to 902,000 after SES adjustment. SES differences between African-Americans and whites appear to explain all the HRQL disparity but only half the mortality disparity. Better understanding of the disparate effects of SES may inform interventions to address health disparities adversely affecting African-Americans.

Introduction

African-Americans are at significantly greater risk of morbidity and premature mortality than whites, with most studies showing a 30% higher age-adjusted risk of mortality (Arias, Anderson, Kung, Murphy, & Kochanek, 2003). Socio-economic status (SES) accounts for much of this difference, but differences in mortality persist after adjustment (Kawachi, Daniels, & Robinson, 2005; Williams, 1999). A higher prevalence of hypertension, HIV, ischemic heart disease, stroke, and cancer appears to be driving higher rates of mortality in this group (Sorlie, Rogot, Anderson, Johnson, & Backlund, 1992; Wong, Shapiro, Boscardin, & Ettner, 2002).

To our knowledge, the burden of disease among African-Americans in the US has not been reported. Burden of disease analyses provide useful information on overall societal impact of illness, ideally combining information on both morbidity and mortality (Field & Gold, 1998; Michaud, Murray, & Bloom, 2001). Recently, it has become possible to quantify the overall annual and lifetime morbidity and mortality in a single measure, the quality-adjusted life year (QALY).

The QALY is based on a subjective quantification of illness called health-related quality of life (HRQL). The advantages of using HRQL scores are that: (1) they can be used to adjust years of life lived and lost, thereby producing a summary measure that captures both morbidity and mortality in a single number; (2) they capture the cumulative effects of multiple conditions; and (3) they capture both psychological and physiological dimensions of illness. Because they are based on perceptions and include psychological dimensions of illness, however, two individuals with the same biomedical disease of the same severity can report different scores. Further, HRQL scores cannot capture morbidity not affecting health perceptions.

Quantification of the burden of disease due to race and the influence of SES on this burden may assist policymakers in prioritizing social interventions (Field & Gold, 1998). In this study, we examine the burden of disease borne by African-Americans relative to whites before and after adjusting for income and education. We use comprehensive outcome measures, including annual years of life lost (YLL) and years lost to HRQL impairments. We also examine the losses among individuals over a lifetime. Finally, we examine racial differences in mortality and HRQL by gender and SES.

Section snippets

Overview and definitions

In this study, we examine life expectancy and quality-adjusted life expectancy (QALE) among adult African-Americans relative to whites, excluding Hispanics, before and after adjusting for SES. We also examine annual losses, including the number of deaths, the YLL, and QALYs lost to HRQL impairments alone.

A QALY is a summary measure of population health that includes both morbidity and mortality. One QALY is equal to 1 year of life lived in perfect health, and QALE is the life expectancy in

Calculations

Analyses were conducted using STATA (version 8.2, StataCorp, College Station, TX) and SUDAAN (version 8.0.1, Research Triangle Institute, Research Triangle Park, NC) statistical packages that allow adjustment for the complex sampling design used in the MEPS and NHIS.

Linear regressions were used to derive age-group specific EQ-5D Index scores for persons 18 and older. Cox proportional hazard survival models were used to generate the hazard ratios (HRs). Analyses compared African-Americans

Results

Table 1 shows the demographic profile of the MEPS sample for the US overall, for African-Americans, and whites. African-Americans were more likely to be younger, female, unmarried, live in a metropolitan statistical area, be uninsured, have worse self-rated health, and have two or more conditions than whites. While African-Americans are about 40% less likely to be married than whites, the likelihood of being a widow is roughly the same for both groups. In this sample, the African-American group

Discussion

Relative to whites, African-Americans suffer 67,000 more deaths annually, resulting in 2.2 million YLL. YLL drop to 1.1 million after adjustment for SES. Total QALYs fall more dramatically with SES adjustment, dropping from 2.3 million to 902,000. This larger drop is attributable to the apparent obliteration of race disparities in HRQL after SES adjustment. The disparate effects of SES on mortality and morbidity differences in African-Americans and whites have also been noted previously.

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