Diabetes mellitus and nontraumatic lower extremity amputation in black and white Americans: the National Health and Nutrition Examination Survey Epidemiologic Follow-up Study, 1971-1992.

BACKGROUND The comparative long-term risk of non-traumatic lower extremity amputation (LEA) in black and white Americans, 2 groups with strikingly different rates of diabetes mellitus, is not known. OBJECTIVE To examine the 20-year incidence of LEA in relation to race and diabetes mellitus. METHODS The 14 407 subjects in the National Health and Nutrition Examination Survey Epidemiologic Follow-up Study were observed prospectively between 1971 and 1992. Prevalent diabetes mellitus was ascertained at the baseline examination, and incident diabetes mellitus, during follow-up. Lower extremity amputation was ascertained from hospital discharge records. Cox regression analysis was used to estimate associations between race, diabetes mellitus, and risk of first LEA. RESULTS During the study period, 158 LEAs occurred among 108 subjects. While black subjects constituted 15.2% of the cohort, they represented 27.8% of the subjects with amputation (P = .002). The 20-year age-adjusted rate ratio of first LEAs for black subjects-white subjects was 2.14. Regression analyses confirmed the importance of diabetes mellitus as a key LEA risk factor. The association between prevalent diabetes mellitus and LEA risk was substantially higher (relative risk [RR], 7.19; 95% confidence interval [CI], 4.61-11.22) than that for incident diabetes mellitus (RR, 3.15 [CI, 1.84-5.37]), highlighting the importance of diabetes mellitus duration on LEA risk. While preliminary analyses adjusted for age and diabetes indicated a significant association between race and LEA risk (RR, 1.93 [95% CI, 1.26-2.96]), the effect of race diminished (RR, 1.49 [95% CI, 0.95-2.34]) following adjustment for education, hypertension, and smoking. CONCLUSIONS Although black subjects experienced higher age- and diabetes mellitus-adjusted rates of amputation than their white counterparts, a combination of social and environmental factors may account for the apparent ethnic difference. More research into nonbiological factors associated with LEA may reduce the occurrence of these procedures in both black and white individuals.