Ethnic differences in ankle brachial index are present in middle-aged individuals without peripheral arterial disease

Introduction: To better understand the basis for previously reported ethnic differences in ankle brachial index (ABI), we investigated whether these differences were present in individuals without known peripheral arterial disease (PAD). Methods: We used data from National Health and Nutrition Examination surveys (NHANES 1999-2004) to determine whether ethnic differences were present in respondents without PAD (1 ≤ ABI ≤ 1.3). We assessed whether ethnicity was an independent predictor of ABI and ankle systolic blood pressure (SBP) in linear regression models that adjusted for conventional and novel cardiovascular risk factors. To minimize effects of atherosclerosis on ABI, we studied adults aged ≤ 60 years, and also repeated our analyses in a subset aged ≤ 50 years that did not have risk factors for PAD. Results: 3348 participants aged ≤ 60 years were included in the study. Mean ABI was 1.11 in non-Hispanic Blacks (NHB) and 1.13 in non-Hispanic Whites (NHW) (P < 0.0001). In multivariable linear regression analysis that adjusted for age, gender, ethnicity, smoking, height, diabetes, brachial SBP, dyslipidemia, diabetes, renal function, concurrent cardiovascular disease, and plasma levels of homocysteine, fibrinogen and C-reactive protein, NHB had lower ABI than NHW (β = - 0.03 ± 0.004, P < 0.00001). Although, NHBs had higher ankle SBP than NHWs (by 5.4 mm Hg), NHBs had a lower mean ankle SBP (β = - 3.663 mm Hg ± 0.500, P < 0.0001) after adjusting for clinical covariates, including brachial SBP, in multivariable analysis. Conclusion: Ethnic differences in ABI are present in middle-aged adults at low risk for peripheral atherosclerosis.