Body Mass Index Shown to be Obsolete

According to the results of recent standardized case-controlled study, changing the standard from body mass index (BMI) to waist-to-hip ratio would improve accuracy of cardiovascular (CV) risk assessment across ethnic and racial lines. The team, lead by Salim Yusuf, MBBS, PhD, from Hamilton General Hospital-McMaster Clinic in Ontario, Canada, reported their findings in the November 5, 2005 issue of The Lancet.

Waist-to-hip ratio shows a graded and highly significant association with myocardial infarction risk worldwide. BMI is a calculated number, based on height and weight, used to compare and analyze the health effects of body weight on human bodies of all heights. Specifically, BMI is equal to the weight of a person divided by the square of the person's height. It was developed by Adolphe Quetelet between 1830 and 1850. According to the authors, this proposed redefinition of obesity based on waist-to-hip ratio instead of BMI increases the estimate of myocardial infarction attributable to obesity in most ethnic groups. The authors of this study, called the INTERHEART Study, previously identified 9 easily measured risk factors for heart disease in the summer of 2004.

The INTERHEART Study was a standardized case-control study of acute myocardial infarction (MI). The patient pool consists of 27,098 participants of varying ethnicity from 52 countries. 14,637 of the patients served as controls while the remain 12,461 were cases of MI. The investigators evaluated the relationship between BMI, waist and hip circumferences, and waist-to-hip ratio to MI overall and in each ethnic group.

BMI at first showed a modest, graded association with MI. However, this association was shown to be nonsignificant after adjustments were made to account for several risk factors. Waist-to-hip ratio and waist and hip circumferences, on the other hand, were highly associated with risk of MI, even after adjustment for other risk factors. The population-attributable risks for MI for increased waist-to-hip ratio in the top two quintiles (i.e. the top two-fifths) was 24.3% compared with 7.7% for the top two quintiles of BMI.

Various national bodies and independent medical institutions in different countries have openly supported this study and its finds. These supporters include The Canadian Institutes of Health Research, the Heart and Stroke Foundation of Ontario, the International Clinical Epidemiology Network, AstraZeneca, Novartis, and The Canadian Institutes of Health Research and the Heart and Stroke Foundation of Canada.

Study limitations include possible underestimation of the true contribution of visceral fat to CV disease risk and the use of a case-control design. In addition, there is an inherent inability to determine the relationship between the different measures of obesity on other outcomes or whether there is an increased risk for some other diseases in leaner subjects.

Article References
INTERHEART: A Global Case-Control Study of Risk Factors for Acute Myocardial Infarction, site accessed on 12/03/05

, site accessed on 12/03/05