Thursday, December 28, 2006

Belly Size Predicts Heart Disease Better Than Obesity

A new study suggests that the size of your belly is a better predictor of heart disease than how obese you are overall.

The research was led by Carlos Iribarren of the Research Division of Kaiser Permanente of Northern California in Oakland and is published in the American Journal of Epidemiology.

Body Mass Index (BMI) was once used as a measure to predict heart disease risk. However, you could have a high BMI because you are muscular as opposed to fat. So the scientists in this study decided to look at another factor known as SAD, short for sagittal abdominal diameter, a measure of "visceral obesity".

SAD is also called "supine abdominal height" which has been used to predict mortality in men, and is a measure of the girth around the abdomen at a height that is half way between the top of your pelvis and your lower ribs. It is considered a more reliable measure of a person's girth than the waistline, and the measurement is taken by a health professional using a caliper.

The scientists performed a cohort study involving 101,765 male and female members of the Kaiser Permanente of Northern California who had been through health checks between 1965 and 1970 where their SAD was recorded, and who were followed up 12 years later.

After adjusting for a number of social and lifestyle factors such as age, sex, education, BMI, smoking, alcohol and HRT in women, they found that men in the top 25% of SAD girth measurement had a 42 per cent higher risk of coronary heart disease (CHD) than those in the bottom 25% of SAD girth measurement. For women the figure was 44 per cent.

Iribarren and his team also looked at the results within categories of BMI. They found that within the same BMI range, the SAD measure was a reliable predictor of CHD risk. In other words, two people with the same Body Mass Index (even if their weight was "normal") would effectively have different risks of developing CHD depending on the size of their belly - the larger the belly the bigger the risk.

They also found that SAD was a consistent predictor for CHD across racial groups. However, the younger a person was, regardless of race, the stronger the link between SAD and eventually having CHD. The team found this to be unsurprising since the younger you are when you develop a large belly the more likely you are to have complications later in life.

The researchers concluded that "standing sagittal abdominal diameter was a strong predictor of CHD independently of BMI and added incremental CHD risk prediction at each level of BMI".

"Value of the Sagittal Abdominal Diameter in Coronary Heart Disease Risk Assessment: Cohort Study in a Large, Multiethnic Population."

Carlos Iribarren, Jeanne A. Darbinian, Joan C. Lo, Bruce H. Fireman and Alan S. Go.
American Journal of Epidemiology 2006 164(12):1150-1159; doi:10.1093/aje/kwj341

Association for the Study of Obesity (UK).

Written by: Catharine Paddock
Writer: Medical News Today

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