BARCELONA — Although body mass index is a poor predictor of mortality from myocardial infarction in patients with diabetes, this measure should not be discounted altogether, Dr. Jonathan Shaw said at an international congress on prediabetes and metabolic syndrome.
“Within every tertile of BMI there is increasing risk with increasing waist-to-hip ratio, and with every tertile of waist-to-hip ratio there is increasing risk with [increasing] BMI, so both parameters give different information,” said Dr. Shaw, who is director of clinical research at Australia's Monash University, Clayton, Victoria. However, he added, BMI, waist-to-hip ratio, and waist circumference “are just proxy measures for the real problem: visceral obesity.”
Analyses of epidemiologic data looking at how BMI and waist-hip ratio predict cardiac dysfunction, such as those presented in the Heart Outcomes Prevention Evaluation study (N. Engl. J. Med. 2000;342:145–53), suggest that although BMI has little relation to mortality, there is a stronger association for waist circumference and waist-to-hip ratio. “Two individuals with the same BMI and waist circumference can have different depositions of visceral fat, so measurements of central obesity might be better at predicting MI than BMI,” Dr. Shaw said.
So how good is waist circumference at predicting risk? According to Dr. Shaw, Japanese data from 2002 (Circ. J. 2002;66:987–92) show a correlation between waist circumference and visceral fat, although the volume of this fat can vary between 40 cm
“Waist circumference was a significant predictor of changes in each of the other parameters, whereas none of the others predicted changes. Therefore, waist circumference seems to come before [the other parameters] and might be close to the core [driver of risk],” Dr. Shaw said.
In addition, cross-sectional associations between waist circumference and other risk factors or components of metabolic syndrome show that with increasing waist circumference, there is increasing prevalence of other risk factors. Dr. Shaw added that although there is little doubt that central obesity predicts cardiovascular disease risk, whether or not waist circumference and waist-to-hip ratio are independent of other risk factors is not yet confirmed.
Data from the AusDiab study reported by Dr. Shaw show that the greatest increases in waist circumference are occurring in younger people, and changes are 50% greater in women than in men. “If there is a target for public health campaigns to modify behavior, it is young women who need to be targeted,” Dr. Shaw said.