November 14, 2005
In the November 5 issue of Lancet, investigators from Ontario report that a patient's waist-to-hip ratio (WTHR) is a better predictor of heart attack than their body-mass index (BMI).
This result comes from a recent analysis of the INTERHEART study, which is being conducted in 52 countries. Investigators studied the rate of heart attack in the more than 27,000 patients participating in this study, and compared the incidence of heart attack to their BMI and ther WTHR. They found that BMI is indeed a predictor of heart attack, but is a relatively weak predictor when other risk factors (such as diabetes, smoking, cholesterol, diet, activity and hypertension) were taken into account. In contrast, an elevated WTHR was a strong predictor of MI even after the statistics were adjusted for these other risk factors.
To calculate the WTHR, you should measure both your waist and hips in inches (or centimeters,) then divide the waist measurement by the hip measurement. In women, the ratio should be 0.8 or less, and in men it should be 1.0 or less. Thus, in women the waist should be narrower than the hips, and in men the waist should be narrower or the same as the hips.
Scientists have known for the past few years that how fat is distributed in the body is at least as important as how much fat is in the body. Fat that is accumulated in the abdomen (leading to increased waist size, a pattern doctors refer to as "apple shape") causes more metabolic disruption than fat that is distributed in the hips or thighs (a pattern doctors refer to as "pear shape"). So, for instance, most patients with metabolic syndrome have increased WTHR.
This new finding appears fairly solid. What does this mean to people who are worried about their cardiac risk?
For one thing, it means that people who are not particularly overweight are still at increased risk if their waist size is increased. On the other hand, it means that some overweight people (the pear-shaped ones) may not have greatly increased risk, as long as their other risk factors are under control, and their extra weight is distributed so as to pad their thighs and butts.