More Support for Waist-to-Hip Circumference Over BMI to Predict CHD

December 12, 2007 — Another study is once again suggesting that waist-to-hip ratio is more sensitive than body mass index (BMI) at predicting risk of subsequent coronary disease [1]. Writing in an early online edition of Circulation, Dr Dexter Canoy (University of Cambridge, UK) and colleagues report that increased abdominal obesity — measured in terms of waist-to-hip ratio, was more "consistently and strongly" predictive of coronary heart disease (CHD) than BMI among men and women participating in the European Prospective Investigation Into Cancer and Nutrition in Norfolk (EPIC-NORFOLK) study.
"People in general think that type of body shape is associated with an unhealthy lifestyle, but what we've shown is that even if you take into account habits like smoking, alcohol intake, or sedentary lifestyle, and you take into account what we already know are important predictors of CHD such as hypertension and hyperlipidemia, you still have an excess risk if you have a higher waist-to-hip ratio."
Canoy et al tracked CHD events over a mean of almost ten years among almost 25,000 men and women between the ages of 45 and 79 at baseline. They found that risk of developing CHD increased with higher baseline waist-to-hip ratios, even after adjusting for BMI and other cardiovascular disease (CVD) risk factors. Waist circumference alone was also a predictor of CHD events, but the predicted risk using waist circumference alone tended to be lower than that of waist-to-hip ratio. Similarly, hazard ratios calculated using BMI were attenuated when Canoy et al adjusted for waist-to-hip ratio, suggesting that BMI may not be as sensitive a predictor of disease as waist-to-hip ratio, an observation also seen in a recent analysis of the Dallas Heart Study cohort [2] and in the INTERHEART study [3], as reported by heartwire.
In Canoy et al's study, an analysis that adjusted for waist-only measurements, BMI, and other CHD risk factors, indicated that for every increase of roughly 6.5 cm (2.5 inches) in hip circumference for men, and for roughly 9 cm (3.5 inches) in women, risk of developing CHD was reduced by 20%.
Measure the hips, height, weight, and waist
"We normally use BMI to confirm obesity, and in the last few years there has also been this concept of using waist circumference alone. And what we found out is that if you do not take into account hip circumference, the prediction associated with waist circumference is underestimated. We're not saying people should develop a big hip circumference to protect themselves from risk, but for any body size, those with bigger hips tended to be associated with lower risk, and that hasn't been shown in many studies."
Canoy emphasized that the findings do not necessarily imply that BMI should be dropped as a means of categorizing patients, nor that a change is warranted in the management of obese patients — in whom risk is undoubtedly increased and efforts should focus on losing weight, eating better, and increasing physical activity. Rather, physicians may need to pay close attention to waist and hip measurements in people who are normal weight, or just overweight, women especially.
"In our study, in men who were obese and had lower waist-to-hip ratios, their rates of CVD tended to be slightly lower than if they had high waist-to-hip ratios. But in women, at all levels of BMI, both BMI and waist-to-hip ratio were strongly predictive of heart disease."
The EPIC-Norfolk Study is supported by Cancer Research United Kingdom, the Medical Research Council, the Stroke Association, British Heart Foundation, Department of Health, Europe Against Cancer Programme Commission of the European Union, Food Standards Agency, and Wellcome Trust. Dr. Canoy was supported by Cambridge Commonwealth Trust/Cambridge Overseas Trust and Christ's College. The other study authors have disclosed no relevant financial relationships.
Sources
Canoy D, Boekholdt SM, Wareham N, et al. Body fat distribution and risk of coronary heart disease in men and women in the European Prospective Investigation Into Cancer and Nutrition in Norfolk Cohort. A population-based prospective study. Circulation 2007; DOI: 10.1161/CIRCULATIONAHA.106.673756. Available at: http://www.circ.ahajournals.org.
See R, Abdullah SM, McGuire DK, et al. The association of differing measures of overweight and obesity with prevalent atherosclerosis. J Am Coll Cardiol. 2007;50:752-759.
Yusuf S, Hawken S, Ôunpuu S, et al. Obesity and the risk of myocardial infarction in 27,000 participants from 52 countries, a case-controlled study. Lancet. 2005;366:1640-1649.