Abstract 1905: Intrinsic Contribution of Gender and Ethnicity to Normal Ankle-Brachial Index Values: The Multi-Ethnic Study of Atherosclerosis
Background- Several studies report a higher prevalence of peripheral arterial disease (PAD) among blacks. Some surveys report higher PAD rates in women. Almost all of them based their PAD definition on an ankle-brachial index (ABI) <0.90. We hypothesized that beyond known disparities in risk factors levels contributing to different PAD prevalence in gender and ethnic subgroups, gender and ethnicity per se influence the normal ABI values, and an ABI threshold disregarding gender and ethnicity might partly contribute to prevalence differences.
Methods-In this cross-sectional study of the Multi-Ethnic Study of Athersoclerosis, we selected a subgroup of participants with unequivocally normal ABI (1.00–1.30), and free of any major PAD risk factor (smoking, diabetes, dyslipidemia, hypertension). In a linear model with ABI as the dependent variable, demographic, clinical and biological variables were introduced.
Results-Among 1775 healthy participants, there was no association between ABI and subclinical coronary or carotid disease. Mean ABI values in non-Hispanic whites (NHW), blacks, Chinese and Hispanics were respectively at 1.16, 1.14, 1.14 and 1.16 in men and 1.13, 1.11, 1.11 and 1.12 in women. In the multiple linear regression analysis, male gender, weight, and high education were positively correlated with ABI, and black race, triglycerides, pack-years (in past smokers) and pulse pressure were negatively correlated. In the fully adjusted model, ABI values were 0.02 lower in women vs. men, and 0.02 lower in blacks vs. NH-whites. ABI differences observed in Chinese and Hispanics did not remain significant in the fully adjusted model. Compared to the 0.90 threshold in NHW-men, when the ABI thresholds were reconsidered in women and in blacks according to our findings, PAD rates decreased by 37%, 10% and 36% in NHW-women, black men and black women respectively.
Conclusion- Our data suggest intrinsic ethnic and gender differences in ABI values in healthy subjects. While small in magnitude, these differences are highly significant and can distort population estimates of disease burden.