Metabolic syndrome, obesity highlighted at the AHA epidemiology and prevention meeting

Several presentations at this year’s meeting in Washington, D.C. addressed minority groups and heart disease.

Metabolic syndrome and premature CAD

Metabolic syndrome plays a greater role in the early onset of CAD in women than in men, but no clear-cut association was found in ethnic groups, according to a case-control study at Kaiser Permanente, Oakland, Calif., and Stanford University.

Carlos Iribarren, MD, of Kaiser Permanente, and colleagues examined the risk relation between metabolic syndrome and premature CAD and if association differs between gender or race/ethnicity.

Metabolic syndrome was associated with a 5.1 odds ratio of premature CAD in men and 7.7 in women. In a gender-adjusted analysis stratified by race/ethnicity, however, corresponding odds ratios were 7.9 in blacks, 6.6 in whites, 5.5 in Hispanics and 5.4 in Asians.

Four-hundred-eighty-nine cases presented at the clinic with a definite acute MI, a hospitalization for angina with a confirmed stenosis or a revascularization procedure. Men were younger than 45, women were younger than 55. “One remarkable finding about these cases was that 90% were on some kind of cholesterol-lowering medication,” said Iribarren.

Controls were 727 people with no history of CVD matched on age, gender and race/ethnicity.

“Diabetes was a powerful contributor to early onset coronary disease especially in women,” said Iribarren. “As far as the individual components, we found that hypertension and low HDL were the major drivers of the association between metabolic syndrome and early onset of CAD. The implication, therefore, of our findings are that rather than focusing on the diagnosis of the syndrome itself, attention should be turned to the individual components, particularly hypertension and low HDL,” he said.

For more information:

• Iribarren C, Fortmann SP, Husson G, et. al. Metabolic syndrome and premature coronary artery disease: Is the association equally important across genders and race/ethnic groups?

Criteria for obesity

Criteria for overweight and obesity have been primarily developed in European populations, leading to controversy as to whether these criteria apply adequately to South Asian and Chinese populations. Fahad Razak, BASc, of the Population Health Research Institute, McMaster University, Hamilton, Canada, and colleagues have devised a method to compare metabolic risk associated with a specific level of BMI in South Asian, Chinese and European Canadian populations.

“There is an emerging body of evidence that suggests that there is an elevated risk for CVD in South Asians and Chinese even within normal BMI ranges of less than 25.0 kg/m². Because of this, there have been a number of prior attempts to redefine BMI ranges for overweight and obese in South Asians and Chinese,” said Razak.

Participants were drawn from the Study of Health Assessment and Risk in Ethnic (SHARE) groups, including 300 South Asian, 291 Chinese, 301 Aboriginal and 305 European Canadians.

Researchers used principal components factor analysis to derive underlying latent factors associated with 13 clinical and biochemical markers of overweight and obesity. Each factor was used as the dependent variable in regression models composed of the independent variables age, gender and BMI, according to the abstract.

“What we are proposing is a new approach to choosing outcomes. For example, examine levels of fasting glucose as a continuous marker rather than whether an individual has diabetes or not. Also, use all major relevant risk factors for metabolic abnormalities of CVD rather than a subset. So if we are interested re-setting obesity cut-points for BMI with respect to where abnormalities in glucose metabolism emerge, don’t rely just on fasting glucose levels – use insulin levels and any other relevant markers,” said Razak.

Razak and colleagues suggest that major revisions are needed for the use of BMI levels as criteria for overweight and obesity in South Asians and Chinese. The models in this research indicate that thresholds for obesity (BMI = 30.0 in Europeans) in these populations may need to be lowered by about five units. This will lead to a greater prevalence of overweight and obesity in South Asians and Chinese, researchers said.

For more information:

• Razak F, Anand SS, Yusuf S. Need for substantial revision of criteria for overweight and obese among South Asians and Chinese compared to Europeans to predict the risk of metabolic abnormalities.

Adiposity, environmental factors

Energy expenditure varies between native Africans and African-Americans, but when energy expenditure is adjusted for weight, other environmental factors may lead to the greater rate of obesity, CHD mortality and metabolic syndrome in U.S. women, according to a study presented here.

Researchers compared energy expenditure and obesity between 197 black women from Chicago and 206 Yoruban women from southwestern Nigeria in the same age brackets. “It is not simply physical activity levels that are driving the differences in obesity between these two groups of women,” said Amy Luke, PhD, of Loyola University Stritch School of Medicine, Maywood, Il.

Physical activity, blood pressure, anthropometrics and fasting plasma insulin, glucose and lipid levels were assessed. The mean BMI of Yoruban women was 23 vs. 30.9 for the U.S. blacks in the study. Yoruban women had less body fat, 29.3% vs. 40%. The U.S. women were more likely to be overweight, have high blood pressure, increased waist circumference, and high insulin and lipid concentrations.

The total physical activity expenditure level was adjusted for weight between the groups. In both groups, there was a significant inverse association between physical activity and BMI, percentage of fat, and waist circumference. At any given level of physical activity, women in the United States had a higher degree of adiposity. “Some other environmental factors are influencing the differences in obesity risk between these two populations and I think it is likely dietary intake,” said Luke.

For more information:

• Luke A, Adeyemo AA, Durazo-Arvizu RA, et. al. Energy expenditure and adiposity in Yoruban and African American women.