Impact of Body Mass Index on the Association of Ankle-Brachial Index With All-Cause and Cardiovascular Mortality

Abstract

Objective: To assess the influence of body-mass index (BMI) on the association of ankle-brachial index (ABI) with mortality. Patients and Methods: We conducted a prospective study of National Health and Nutrition Examination Survey participants enrolled from January 1, 1999 to December 31, 2002 with BMI and ABI data available. ABI categories were 1.3 (high). BMI categories were <30 kg/m2 (nonobese) and ≥30 kg/m2 (obese). Cardiovascular (CV) and all-cause mortality were assessed by National Death Index records. Cox proportional-hazards models and Kaplan-Meier survival estimates were used to compare groups. Results: In total, 4614 subjects were included, with mean age 56±12 years and BMI 28±6 kg/m2. Median follow-up was 10.3 years (interquartile range [IQR]: 9.3 to 11.4 years). Low and high ABI were present in 7% and 8%, respectively. After adjustment, low ABI was associated with increased all-cause and CV mortality in nonobese (hazard ratio [HR] 1.5, 95% CI, 1.1-2.1 for all-cause and 3.0 [1.8-5.1] for CV mortality) and obese individuals (1.8 [1.2-2.7] and 2.5 [1.2-5.6], respectively) compared with reference. High ABI was associated with increased CV mortality in nonobese (2.2 [1.1-4.5]) but not obese patients; it was not associated with all-cause mortality overall or when stratified by BMI. Conclusion: In a US cohort, weight influenced the prognostic significance of high ABI. This may be related to technical factors reducing compressibility of the calf arteries in obese persons compared with those who are nonobese.