The ankle-brachial index and incident cardiovascular events in the MESA (Multi-Ethnic Study of Atherosclerosis).

OBJECTIVES: The purpose of this study was to examine the association of both a low and a high ankle-brachial index (ABI) with incident cardiovascular events in a multiethnic cohort.
BACKGROUND: Abnormal ABIs, both low and high, are associated with elevated cardiovascular disease (CVD) risk. However, it is unknown whether this association is consistent across different ethnic groups, and whether it is independent of both newer biomarkers and other measures of subclinical atherosclerotic CVD.
METHODS: A total of 6,647 non-Hispanic white, African-American, Hispanic, and Chinese men and women age 45 to 84 years from free-living populations in 6 U.S. field centers and free of clinical CVD at baseline had extensive measures of traditional and newer biomarker risk factors, and measures of subclinical CVD, including the ABI. Incident CVD, defined as coronary disease, stroke, or other atherosclerotic CVD death, was determined over a mean follow-up of 5.3 years.
RESULTS: Both a low (<1.00) and a high (≥1.40) ABI were associated with incident CVD events. Sex- and ethnic-specific analyses showed consistent results. Hazard ratios were 1.77 (p<0.001) for a low and 1.85 (p=0.050) for a high ABI after adjustment for both traditional and newer biomarker CVD risk factors, and the ABI significantly improved risk discrimination. Further adjustment for coronary artery calcium score, common and internal carotid intimal medial thickness, and major electrocardiographic abnormalities only modestly attenuated these hazard ratios.
CONCLUSIONS: In this study, both a low and a high ABI were associated with elevated CVD risk in persons free of known CVD, independent of standard and novel risk factors, and independent of other measures of subclinical CVD. Further research should address the cost effectiveness of measuring the ABI in targeted population groups.