Using BMI to assess cardiometabolic risk not ideal for racial/ethnic minorities

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 - Tim Casey
Tim Casey, Executive Editor

Physicians often use body mass index (BMI) to assess people’s cardiovascular disease risk. A recent study suggests, though, that BMI may not be the best way to determine cardiometabolic abnormalities, particularly among minority groups.

The researchers found that 29.1 percent of participants with a normal BMI had the metabolic abnormality but normal weight (MAN) phenotype. The prevalence of MAN was 21.0 percent in whites, 32.2 percent in Chinese Americans, 31.1 percent in African Americans, 38.5 percent in Hispanics and 43.6 percent in South Asians.

The cross-sectional analysis examined community-based cohorts in the MESA (Multi-Ethnic Study of Atherosclerosis) and the MASALA (Mediators of Atherosclerosis in South Asians Living in America) studies.

Results of the National Institutes of Health-funded study were published in the Annals of Internal Medicine on April 3.

The researchers defined normal weight as a BMI from 18.5 kg/m2 to 24.9 kg/m2 for white, African American and Hispanic participants and a BMI from 18.5 kg/m2 to 22.9 kg/m2 for South Asian and Chinese American participants. They defined cardiometabolic abnormality as having two or more of the following: high fasting glucose, low high-density lipoprotein cholesterol, high triglyceride levels and hypertension.

Compared with whites, the prevalence of MAN was approximately 100 percent greater in South Asians, 80 percent greater in Hispanics and 50 percent greater in Chinese and African Americans. After adjusting for multiple variables, South Asian, Chinese, African American, and Hispanic race/ethnicity were independently associated with MAN.

Meanwhile, for the equivalent number of cardiometabolic abnormalities at a BMI of 25 kg/m2 in white participants, the corresponding BMI values were 22.3 kg/m2 in African Americans, 21.5 kg/m2 in Hispanics, 20.5 kg/m2 in Chinese Americans, and 18.9 kg/m2 in South Asians.

The researchers acknowledged their analysis had a few limitations, including that the studies collected data at different time periods (2000 to 2002 for MESA and 2010 to 2013 for MASALA), which could have resulted in different prevalences of overweight and obesity. The studies also used different food-frequency questionnaires. In addition, the studies were not nationally representative, so the results might not be generalizable to younger people or South Asians and Chinese Americans born in the United States.

“Our findings suggest a high prevalence of cardiometabolic abnormality among normal-weight persons, particularly those in racial/ethnic minority populations,” the researchers wrote. “This disparity cannot be explained by differences in demographic, behavioral, or ectopic fat measures. Therefore, clinicians using overweight and obesity as the main criteria for cardiometabolic screening, as currently recommended by the U.S. Preventive Services Task Force for diabetes testing, may fail to identify cardiometabolic abnormalities in many patients from racial/ethnic minority groups. Although the Task Force recommends earlier screening in racial/ethnic minority populations, testing for cardiometabolic abnormalities in normal-weight and under- weight members of these groups also may be an important consideration. Future research is needed to identify the prospective associations between MAN and incident diabetes and cardiovascular disease in various racial/ethnic groups.”