Evaluating body-mass index (BMI), waist circumference and waist-to-hip ratio, singly or in combination, did not improve cardiovascular disease risk prediction when systolic blood pressure, diabetes or lipid information were added to the mix, according to an analysis published in the March 10 issue of Lancet.
“Guidelines differ about the value of assessment of adiposity measures for cardiovascular [CV] disease risk prediction when information is available for other risk factors,” the authors wrote.
During the study, principal investigator John Danesh, of the University of Cambridge in the U.K., and his colleagues from the Emerging Risk Factors Collaboration Coordinating Centre in Cambridge, England, evaluated 58 prospective studies that included 221,935 patient records from 17 countries to evaluate the separate and combined associations of BMI, waist circumference and waist-to-hip ratio with risk of first-onset of CV disease.
Of the included records, patients had a mean age of 58 years old, 56 percent were women and 58 percent of patients were from Europe, 33 percent from North America, 4 percent from Australia and 4 percent were from Japan.
Of the 221,935 available records, serial adiposity assessments were made in 63,821 patients. In patients with a BMI of 20 kg/m2 or higher, the hazard ratio was 1.23 with BMI, 1.27 with waist circumference and 1.25 with waist-to-hip ratio after the researchers adjusted for age, sex and smoking status. There was a log-linear association of BMI, waist circumference and waist-to-hip ratio with risk of coronary heart disease and ischemic stroke.
After the researchers adjusted for systolic blood pressure, a history of diabetes and total and HDL cholesterol, the aforementioned hazard ratios were 1.07, 1.10 and 1.12, respectively.
“Addition of information on BMI, waist circumference, or waist-to-hip ratio to a cardiovascular disease risk prediction model containing conventional risk factors did not importantly improve risk discrimination, nor classification of participants to categories of predicted 10-year risk,” the authors reported.
The excess risk of CV disease associated with BMI, waist circumference and waist-to-hip ratio was three-to-four times stronger at ages 40 to 59 years than at over 70 years.
“Because excess adiposity is a major determinant of the intermediate risk factors noted above, our findings underscore the importance of controlling adiposity to help prevent cardiovascular disease,” the authors wrote.
In addition, the researchers reported that a combination of BMI and waist-to-hip ratio provides only a quarter of extra predictive information provided by total and HDL cholesterol, emphasizing that like other studies have suggested, adopting a strategy that uses waist-to-hip ratio rather than BMI as the principle measure of adiposity may not be most beneficial.
Results of the study showed that measuring abdominal adiposity—waist circumference and waist-to-hip ratio—could best BMI as indicators of visceral fat accumulation. However, BMI, waist circumference and waist-to-hip ratio have similar strength associations with CV disease risk.
The researchers concluded that the findings should “help to clarify divergent recommendations in cardiovascular disease guidelines about clinical measures of adiposity in assessment of risk.”
The analysis was funded by the British Heart Foundation and U.K. Medical Research Council.
In an accompanying editorial, Rachel R. Huxley and David R. Jacobs Jr., PhD, of the University of Minnesota in Minneapolis, wrote "the study dispelled previous hope that assessment of body size could replace the cost, time, and inconvenience of blood lipids assay," which could be an important factor in locations where resources are scarce.
In addition, Huxley and Jacobs Jr. added that the inclusion of BMI and waist circumference only "marginally compensate for the lack of information about total and HDL cholesterol in a risk-prediction model."
The authors said that questions still remain such as to what extent a middle-age risk factor represents the status of the factor long before and after its measurements. The authors said this is less of an issue with BMI than for those intermediate risk factors.
"Do the new data from the Emerging Risk Factors Collaboration mean that we should stop measuring BMI?" Huxley and Jacobs Jr. asked. They concluded that BMI is still important and used with clinical judgement, despite its possible lack of sensitivity,