Waist-Hip Ratio Tops BMI and Waist Alone for Predicting Atherosclerosis

DALLAS, Aug. 13 -- For assessing obesity's impact on atherosclerosis risk, the waist-to-hip ratio tops body mass index and waist circumference, investigators here found.
With a high waist-hip-ratio, there was a significantly greater level of coronary artery calcium (an atherosclerosis surrogate) in men and women than a high BMI (P<0.001) or large waist circumference (P<0.01), they reported online in advance of the Aug. 21 issue of the Journal of the American College of Cardiology.
In a large population-based cohort, a comparison of the highest and lowest waist-to-hip ratios showed a 91% increase in prevalent coronary artery calcium, whereas neither BMI nor waist circumference had a positive association with aortic plaque, said James A. de Lemos, M.D., of the University of Texas Southwestern Medical Center, and colleagues.
The finding that the highest quintile of waist-to-hip ratio remained associated with coronary artery calcium and aortic plaque after adjustment for coronary risk factors "also suggests that major risk factors alone do not fully explain the influence of waist-hip-ratio, and that other less well-understood effects related to obesity may contribute to increased atherosclerosis in this cohort," the authors concluded.
Although obesity increases the risk of cardiovascular mortality, whether the relationship is mediated by increased atherosclerotic burden had been unclear, noted to Dr. de Lemos and colleagues.
Their analysis involved 2,744 participants in an ongoing study of heart disease in a multiethnic population. Each participant underwent an extensive clinical examination, laboratory evaluation, abdominal MRI, and electron beam computed tomography (EBCT) measurement of coronary artery calcium. Prevalent atherosclerosis was defined as > 10 Agatston units by electron-beam CT and detectable aortic plaque measured by MRI.
Investigators divided the participants into gender-specific quintiles of BMI, waist circumference, hip circumference, and waist-to-hip ratio. Univariate logistic regression modeling was used to determine odds ratios for prevalent coronary calcium by each quintile of obesity. Multivariate models included traditional cardiovascular risk factors.
EBCT revealed measurable coronary calcium in 583 (21%) of the study participants, and MRI demonstrated aortic plaque in 976 of 2,504 (39%) participants who underwent abdominal imaging.
Analysis of prevalent coronary calcium by obesity category demonstrated a J-shaped association with BMI, whereas prevalence increased in a stepwise fashion across quintiles of waist circumference and waist-to-hip ratio (P<0.001). After adjustment for conventional risk factors, prevalent coronary calcium was significantly increased in the highest versus lowest quintile of waist-to-hip ratio (odds ratio 1.91) but not in any quintile of BMI or waist circumference.
Looking at aortic plaque, the highest quintile of waist-to-hip ratio almost tripled the risk of prevalent aortic atherosclerosis compared with the lowest quintile (OR 2.97). Neither BMI nor waist circumference had a significant association with aortic plaque in univariate analysis. After adjustment for traditional risk factors, both the fourth and fifth quintiles waist-to-hip ratio had a positive association with aortic plaque.
"Because detectable [coronary calcium] is a nearly 100% specific finding for atherosclerosis and because prevalent disease may precede events for years, our findings suggest that obesity itself may play a role in the initiation and propagation of the atherosclerotic process," the authors concluded.
In an interview, study co-author Amit Khera, M.D., said the results indicate that "it's probably more important to look in the mirror than it is to look at the scale" when evaluating obesity's impact on coronary risk (see accompanying video).
The authors had no disclosures. The study was supported by the Donald W. Reynolds Foundation, the United States Public Health Service, and the National Institutes of Health.Primary source: Journal of the American College of CardiologySource reference: See R et al. "The association of differing measures of overweight and obesity with prevalent atherosclerosis." J Am Coll Cardiol 2007;50:752-759.