Introduction:
Metabolic syndrome (MetS) and low ankle-brachial index (ABI) share interrelated cardiovascular risk factors and are thus both strong indicators of an atherosclerotic process. However, few clinicians consider metabolic syndrome as a risk factor for abnormally low ABI and subsequent peripheral arterial disease. Therefore, it is necessary to highlight the relationship between abnormal ABI and MetS and the role of cardiovascular risk factors on this relationship.
Hypothesis:
We hypothesize that persons with MetS compared to those without, are more likely to experience abnormally low ABI even after accounting for additional cardiovascular risk factors not defined in the MetS.
Methods:
The eligible population consisted of 7,458 men and women aged 40 years and older, with and without cardiovascular disease (CVD) participating in The National Health and Nutrition Examination Survey from 1999-2004. Subjects were evaluated, according to the American Heart Association definitions, for abnormally low ABI < 1.0 (which included borderline low and low ABI) and metabolic syndrome with ≥ 3 of the following 5 components; central obesity, hypertriglyceridemia, low HDL cholesterol, hyperglycemia and hypertension. Ordinal logistic regression models were used to identify relationships between abnormal ABI and MetS, with adjustments for additional cardiovascular risk factors in multivariate models.
Results:
Participants with metabolic syndrome, as compared to those without, were 1.51 (95% CI, 1.01-2.26) times more likely to experience abnormally lower values of ABI after adjusting for gender, race, education, smoking and CRP. The relationship between abnormal ABI and MetS was modified by age (p value 0.01) but not by gender (p value 0.10) or race (p value 0.09). Additionally, odds of a lower ABI was highest for those with 4-5 components of MetS compared to those with 0-2 components (OR, 2.22; 95% CI, 1.44 to 3.43). Examining individual MetS components in fully adjusted models revealed that hypertriglyceridemia (OR, 1.69; 95% CI, 1.16 to 2.46) and low HDL cholesterol (OR, 1.81; 95% CI, 1.15 to 2.87) were associated with higher odds of abnormal ABI.
Conclusions:
In conclusion, the presence of MetS in adults with and without CVD was associated with abnormally low ABI, even after accounting for additional cardiovascular risk factors not defined by the MetS. This study suggests that timely clinician awareness of abnormally low ABI in persons with at least three MetS components, hypertriglyceridemia or low HDL cholesterol, may be useful in preventing the debilitating effects of peripheral artery disease.