NEW ORLEANS — Waist circumference is increasingly supplanting body mass index as the preferred indicator of obesity-related cardiovascular risk, both in research studies and clinical practice, Robert H. Eckel, M.D., said at the annual scientific sessions of the American Heart Association.
“Many people believe we have been overfocusing on body mass index. … I think the database worldwide is suggesting waist circumference is a better measure of risk than weight itself or BMI,” said Dr. Eckel, who is AHA president-elect as well as professor of medicine at the University of Colorado, Denver.
“Waist circumference is a vital sign in my clinic, like blood pressure and pulse,” Dr. Eckel added.
Several studies presented at the AHA meeting underscored the point that for assessing cardiovascular risk, where a person's excess body fat is located is more important than how overweight or obese the person is.
For example, Xavier Jouven, M.D., presented an update on the landmark Paris Prospective Study I, which enrolled more than 7,000 healthy middle-aged French policemen and followed them for more than 20 years, during which there were 118 sudden deaths and 182 nonsudden cardiac deaths.
After adjustment for all the standard cardiovascular risk factors, sagittal abdominal diameter—a measure of abdominal fat—was significantly associated with increased risk of sudden death. BMI was not.
Normal-weight men have traditionally been viewed as being at low risk for sudden death.
So it was unexpected and particularly impressive to find in the Paris study that normal-weight policemen who had a BMI of less than 25 kg/m2 but were in the third tertile for sagittal abdominal diameter had a threefold greater risk of sudden death than did normal-weight men in the first tertile, said Dr. Jouven of the cardiovascular, metabolic, and sudden death epidemiology unit of INSERM, the French national medical research organization, in Villejuif, France.
More than half of the roughly 300,000 sudden deaths occurring each year in the United States constitute the first manifestation of heart disease in previously asymptomatic individuals.
This underscores the importance of trying to pinpoint the risk factors for sudden death as accurately as possible to enhance efforts at prevention, Dr. Jouven stressed.
Abdominal obesity is an established independent risk factor for coronary heart disease, but prior to the Paris study little was known about the relationship between abdominal obesity and sudden death.
The usual measure of obesity is BMI, but this has the disadvantage of combining fat-free mass and fat mass, while providing no information about fat localization, he noted.
In a separate presentation, Khawaja Afza Ammar, M.D., reported on 2,042 randomly selected Minnesotans aged 45 and older who underwent echocardiographic evaluation of left ventricular function along with measures of central, peripheral, and overall obesity.
He found that any of the measures of central obesity—waist circumference, waist-hip ratio, and neck circumference—were more strongly correlated with diastolic dysfunction than were peripheral obesity as measured by skinfold thickness or than overall obesity as reflected in BMI.
In fact, after adjustment for the standard coronary risk factors, BMI and skinfold thickness had little or no relationship with left ventricular dysfunction.
However, waist-hip ratio and the other measures of central obesity did, Dr. Ammar said.
“We think that we have identified central obesity as a more important mediator of congestive heart failure and left ventricular dysfunction,” said Dr. Ammar, director of the treadmill laboratory at Olmsted Medical Center, Rochester, Minn.
“The clinical importance of this study is that instead of measuring weight, height, and BMI, if a doctor is more concerned about a patient developing congestive heart failure it might be more prudent to measure waist circumference or even neck circumference, which is a very easy-to-measure marker of obesity,” he said.
“You do not need to disrobe the patient to measure neck circumference; you can measure it in the corridor. And in our study, neck circumference was almost as strongly correlated with left ventricular dysfunction as were waist circumference and waist-hip ratio,” Dr. Ammar added.