Relationship of Cardiovascular Risk Factors to Racial Differences in Femoral Bypass Surgery and Abdominal Aortic Aneurysmectomy in Massachusetts

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Abstract
Atherosclerosis is more severe in blacks than in whites, but abdominal aortic aneurysms, which have traditionally been thought to have an atherosclerotic etiology, appear to be less common in blacks. Because of this incongruity, we compared risk factor profiles in patients undergoing abdominal aortic aneurysm repair and patients undergoing femoral bypass for atherosclerotic occlusive disease. A dual case-control study was conducted, first, comparing patients who had undergone aneurysmectomy to a control group of patients who had undergone appendectomy; and then comparing patients who had undergone femoral bypass surgery to the same appendectomy controls. We initially used hospital discharge data for the entire state of Massachusetts and, in a second phase, data obtained from a review of medical records from Boston University Medical Center Hospital and Boston City Hospital. The statewide database indicated that rates of femoral bypass surgery were higher in blacks than in whites, but after adjusting for differences in hypertension, diabetes, and low socioeconomic status, the black/white odds ratio for femoral bypass fell to 1.44 (95% confidence interval: 1.08, 1.92). A similar analysis based on the hospital chart review, provided better control of confounding and indicated that there was no racial difference in rates of femoral bypass after correcting for other risk factors (odds ratio = 0.94; 95% confidence interval: 0.40, 2.22; p = 0.90). In contrast, the statewide database found higher rates of abdominal aortic aneurysm surgery in whites, and particularly in white males. Smoking and hypertension were strong risk factors for aneurysmectomy, but diabetes mellitus and socioeconomic status were not. After adjusting for other variables, the black/white odds ratio for aneurysmectomy was 0.29 (95% confidence interval: 0.07, 1.23; p = 0.09). Substantial differences are found in the risk factor profiles for aneurysmal disease and femoral atherosclerotic occlusive disease. Diabetes is a particularly strong risk factor for femoral disease, but not for aneurysmal disease. In addition, blacks had higher rates of femoral bypass surgery in Massachusetts, but the apparent racial difference appeared to be due to a greater prevalence of hypertension, smoking, and diabetes in blacks. In contrast, abdominal aortic aneurysms occurred predominantly in white males, and adjustment for other risk factors further accentuated the greater risk in whites.