Summary

The Multi-Ethnic Study of Atherosclerosis reports on the rates of obesity in different ethnic groups. While obesity and overweight are common among white, African American and Hispanic groups, it is less so among Chinese Americans. The higher the body mass index, the more likely a participant was to have high blood pressure, high cholesterol and other risk factors, foreshadowing a possible 'epidemic' of heart disease to come.

Introduction

We hear a great deal about the epidemic of obesity that is affecting the United States and many other countries. From 1960 to 2000, the proportion of the US population classed as obese went up from 11 percent to 28 percent among men and from 16 percent to 34 percent among women. There is also a link between obesity and cardiovascular risk factors, including some sub-clinical 'markers' of heart disease. As it stands, heart disease linked to obesity may start to wipe out some of the gains in life expectancy that have been achieved in industrial countries.

One interesting facet of the obesity epidemic is how it affects different ethnic groups. The Multi-Ethnic Study of Atherosclerosis was set up by a group of experts funded by the United States National Heart, Lung and Blood Institute and led by researchers at Wake Forest University School of Medicine. The current phase of this work, begun in 2000, provides a valuable opportunity to learn about the impact of the obesity epidemic on different ethnic groups and their heart health (or lack of it).

What was done

A group of 6,814 individuals aged 45 to 84 joined the study. At the start, they did not have heart disease. The researchers made several measurements. First they calculated body mass index (BMI) to find who was obese, overweight or of normal weight. Blood pressure and lipid profile were measured too. Then the researchers measured a number of pre-clinical markers of heart disease: coronary artery calcium, carotid artery wall thickness and left ventricular mass. These are the 'silent' indicators of future heart disease.

What was found

As many as 75 percent of African American, Hispanic and white men were either overweight or obese. And more than 60 percent of white women fell into this category. But only a third of the Chinese Americans were overweight. The researchers say that overall, more than 50 percent of African American women, 40 percent of Hispanic women, 30 percent of African American and Hispanic men and 30 percent of white men and women could be classed as obese. But only five percent of Chinese Americans are obese.

Higher BMI, as you might expect, is linked to higher blood pressure and higher cholesterol, both potent risk factors for cardiovascular disease. When it came to the preclinical markers, obesity was linked to an increase in coronary artery calcium, thickening of the carotid arteries, and a higher left ventricle volume.

What this study means

The fact that overweight and obesity is less common among Chinese Americans may be down to genetic factors or to cultural and lifestyle issues. The good news it, that obesity is not inevitable if you live in the United States. The strong link of obesity to cardiovascular risk factors is confirmation of what medical experts have been warning of for years - obesity is a real health hazard. The researchers will now go on to see if their findings are reflected in development of heart disease in the future. In the meantime, it is clearly worthwhile redoubling efforts to keep to a healthy weight if life expectancy gains in the United States are not to be reversed.