Waist-to-Hip Ratio vs BMI May Be More Accurate Predictor of CV Risk

Chris Street edits in bold.

Wikipedia article Waist to Hip Ratio was updated by Chris Street today:-

WHR not Body mass index (BMI), is the best obesity measure for assessing a person’s risk of heart attack. If obesity is redefined using WHR instead of BMI, the proportion of people at risk of heart attack worldwide increases threefold.^[2][3]

News Author: Laurie Barclay, MD
CME Author: Charles Vega, MD, FAAFP

Release Date: November 7, 2005;

Nov. 7, 2005 — Changing the standard from body mass index (BMI) to waist-to-hip ratio would improve accuracy of cardiovascular (CV) risk assessment across ethnic groups, according to the results of a standardized case-controlled study reported in the Nov. 5 2005 issue of The Lancet. The editorialists suggest that this marker should replace BMI.

Obesity and the risk of myocardial infarction in 27 000 participants from 52 countries: a case-control study
Waist-to-hip ratio, not body mass index (BMI), is the best obesity measure for assessing a person’s risk of heart attack, conclude authors of a study published this week. If obesity is redefined using waist-to-hip ratio instead of BMI, the proportion of people at risk of heart attack increases threefold. Heart-attack patients had a strikingly higher waist-to-hip ratio than people in a control group, irrespective of other cardiovascular risk factors......

"Our findings suggest that substantial reassessment is needed of the importance of obesity for cardiovascular disease in most regions of the world," lead author Salim Yusuf, MBBS, PhD, from Hamilton General Hospital-McMaster Clinic in Ontario, Canada, said in a news release.

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

"Waist-to-hip ratio shows a graded and highly significant association with myocardial infarction risk worldwide," the authors write. "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."

Study limitations include possible underestimation of the true contribution of visceral fat to CV disease risk, case-control design, and inability to determine the relationship between the different measures of obesity on other outcomes or whether there is an increased risk for some diseases in those who are lean.

"The INTERHEART investigators place what seems to be the final nail in the casket for body-mass index as an independent cardiovascular risk factor," Drs. Kragelund and Omland write. "The main message from the new INTERHEART report is that current practice with body-mass index as the measure of obesity is obsolete, and results in considerable underestimation of the grave consequences of the overweight epidemic. A direct consequence of these findings is that, for assessment of risk associated with obesity, the waist-to-hip ratio, and not body-mass index, is the preferred simple measure."

Lancet. 2005;366:1589-1591, 1640-1649

Clinical Context

Risk factors for MI have been extensively studied, but most of this research has focused on individuals in Europe and North America. The INTERHEART study reached out beyond cultures and ethnicities traditionally involved in medical research to include patients in Asia, Africa, the Middle East, and South America. In the original report from this study, published in the Sept. 11 - 17, 2004, issue of The Lancet, the authors found that common risk factors for MI included smoking, raised ApoB/ApoA1 ratio, history of hypertension, diabetes, abdominal obesity, and psychosocial factors. However, the intake of fruits and vegetables as well as alcohol consumption was protective against MI.

These data from the INTERHEART study suggested that waist circumference might be a better predictor of CV risk than another well-known anthropometric measurement, the BMI. The current analysis focuses on this issue.

Study Highlights

• The study was a case-control trial comparing patients with their first MI vs age- and sex-matched controls. Patients with MI were eligible for study participation if they did not have cardiogenic shock or any major chronic illness. Subjects were evaluated in centers in 52 countries and 6 continents.
• Cases and controls were compared in terms of demographic factors, socioeconomic status, lifestyle, medical risk factors, and a personal and family history of CV disease.
• 12,461 cases were compared with 14,637 controls. Logistic regression was used to account for other confounding CV risk factors in comparing anthropometric values.
• For the overall cohort, the mean BMI was lowest in Asia, intermediate in Europe, South America, and Africa, and highest in North America, the Middle East, and Australia. However, waist-to-hip ratio exhibited different geographic trends, being lowest in China, intermediate in North America, Europe, and other parts of Asia, and highest in the Middle East and South America.
• Subjects in the highest quintile of BMI had an OR of MI of 1.44 vs those in the lowest quintile. However, the risk for MI associated with BMI was obviated after adjustment for other risk factors.
• Conversely, subjects in the highest quintile of waist-to-hip ratio had an OR of MI of 1.77 vs those in the lowest quintile. After adjustment for other risk factors, this OR decreased to 1.33, but it remained statistically significant.
• The risk of MI increased progressively with values for waist-to-hip ratio, with no evidence of a threshold. The association between MI and waist-to-hip ratio was significant regardless of BMI, sex, age, or the presence of other CV risk factors.
• The waist-to-hip ratio, waist-to-height ratio, waist circumference, and hip circumference were all better predictors of MI vs BMI. BMI was the worst predictor of MI across all 8 ethnic groups, whereas waist-to-hip ratio was the best predictor in 6 of the 8 groups.