A new US study suggests that waist to hip ratio (WHR) is more closely linked to early signs of heart disease than body mass index (BMI) or waist circumference alone. Even a small pot belly is linked to a higher risk of developing plaque in the arteries compared to having a flat tummy, said the researchers.

The study is published in the August 21st issue of the Journal of the American College of Cardiology (JACC) and was conducted at the University of Texas Southwestern Medical Center in Dallas, US.

Adding inches to the waist significantly increases the risk of cardiovascular disease, said the researchers, even if BMI is in the normal range.

Lead author of the study and Professor of medicine and director of the Coronary Care Unit at the University of Texas Southwestern Medical Center, Dr James A. de Lemos said:

“In our thirties and forties, we often gain three to four inches in the midsection.”

“It’s a day-to-day, meal-to-meal battle, but it’s worth fighting. Even a small pot belly puts us at higher risk when compared to a flat tummy,” he added.

De Lemos and colleagues used records from the Dallas Heart Study, an ongoing research project that is evaluating risk factors for heart disease in a large multiethnic urban population of people whose median age is 45.

The part of the Dallas Heart Study the researchers focused on was a group of 2,744 people who were scanned for signs of plaque in the arteries and in the artery near the heart (aorta), both well known early signs of cardiovascular disease.

The participants were scanned using electron-beam computed tomography (EBCT) which shows up any calcium deposits in the arteries of the body. Calcium deposits in arteries are an early indicator of atherosclerosis, where the arteries become hardened and years later may lead to heart attack. The participants also had magnetic resonance imaging (MRI) scans to look for atherosclerosis in the walls of the aorta, the major artery of the heart.

The scientists used three gender-specific measures of obesity: BMI, waist circumference (WC) and waist to hip ratio (WHR) and assessed their association with coronary artery calcium (CAC), which is derived from the EBCT scan. They also assessed the level of aortic plaque from the MRI scan.

When they looked at the association between the various obesity measures and the signs of arterial disease, the scientists found that WHR was independently linked to increased arterial plaque whereas no independent positive association was found for BMI or WC.

More specifically, using univariate and multivariate analysis the results showed that:

  • CAC prevalence was significantly greater only in the top fifth of BMI compared with the bottom fifth (fifth versus first quintile).
  • Whereas CAC prevalence increased stepwise with each fifth of WHR and WC from the bottom to the top (level of significance, p was less than 0.001 in each case).
  • People in the top fifth of WHR (the largest) were nearly twice as likely to have calcium deposits compared with those in the bottom fifth (the smallest) WHR.
  • After adjusting for standard risk factors such as blood pressure, diabetes, age, smoking and high cholesterol, only WHR was independently correlated with CAC prevalence (odds ratio 1.91 comparing top quintile with bottom), whereas no such association was present for BMI or WC.
  • Similar results were found for aortic plaque, with people in the top fifth of WHR (the largest) being three times more likely to have it compared to those in the bottom fifth (the smallest).
  • Using a statistical test called the c-statistic the results showed that WHR was more strongly linked to CAC prevalence than BMI and WC in men and women (p for WHR was less than 0.001 versus BMI and less than 0.01 versus WC).

The researchers concluded that:

“We discovered that WHR was independently associated with prevalent atherosclerosis and provided better discrimination than either BMI or WC.”

“The associations between obesity measurements and atherosclerosis mirror those observed between obesity and cardiovascular mortality, suggesting that obesity contributes to cardiovascular mortality via increased atherosclerotic burden.”

Commenting on their findings, de Lemos said:

“Middle-aged spread is not healthy, we don’t have to clean our plates. It’s better to throw food out than add it to our waists.”

In a press release from the American College of Cardiology, Dr Raimund Erbel, from the West German Heart Center in Essen said that:

“Using the waist-to-hip measurement to gauge cardiovascular risk has certain clinical advantages.”

“The WHR can be easily measured, taking only a few moments and giving more precise information on the presence of coronary artery calcium than BMI or waist circumference,” added Erbel.

“In addition, although BMI is used more often, it does not identify patients with central obesity, which seems to be related to the metabolic syndrome, insulin resistance and abnormal cholesterol levels. However, most important is that other measures of obesity did not discriminate beyond traditional risk factors, whereas WHR did,” he explained.

Essen said he found the findings “astonishing” and perhaps they were reflected the age distribution of the participants. He suggested that:

“During life, the likelihood of coronary artery calcium increases more in men than in women. It may be that in an older population, in which the duration of risk factor exposure is longer and the likelihood of coronary artery calcium is higher, the association between obesity, as measured by BMI and waist circumference, and signs of early atherosclerosis is stronger.”

“The Association of Differing Measures of Overweight and Obesity With Prevalent Atherosclerosis: The Dallas Heart Study.”
Raphael See, Shuaib M. Abdullah, Darren K. McGuire, Amit Khera, Mahesh J. Patel, Jason B. Lindsey, Scott M. Grundy, and James A. de Lemos.
J Am Coll Cardiol, first published on Aug 6, 2007.

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Written by: Catharine Paddock