A person’s waist size (circumference) is a better predictor of future type 2 diabetes than A1C level (a measure of long-term blood glucose control) in Black adults without diabetes, according to a new study published in the Journal of the American Heart Association.
Black Americans tend to be diagnosed with type 2 diabetes earlier in life than people from other racial or ethnic groups, as pointed out in a Healio article on the study — so it makes sense to look at ways to predict the risk of developing diabetes in this group. By identifying who is at greatest risk for developing prediabetes and type 2 diabetes before either of these conditions develop, it may be possible to encourage lifestyle or other interventions that reduce a person’s diabetes risk — and the risk of future complications, which disproportionately affect Black Americans due to the widespread earlier onset of diabetes.
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Researchers looked at participants in a larger study called the Jackson Heart Study — which evaluated cardiovascular disease risk in Black adults in Mississippi — who did not have diabetes at the start of the study. There were two different phases of the study. The first involved 2,422 adults who were evaluated in a second follow-up exam taking place a median of five years later, at which 300 of them were found to have diabetes — showing a diabetes risk of 24.6 per 1,000 person-years.
Higher waist circumference linked to increased risk of diabetes
After adjusting for numerous factors — including age, sex, education level, job status, diet, physical activity, smoking status, alcohol consumption, blood pressure, and body-mass index (BMI, a measure of body weight that takes height into account) — they found that each standard deviation (a statistical measure of how far a number is from the average) increase in waist circumference was linked to a 56% higher risk of developing diabetes. What’s more, after adjusting for participants’ earlier A1C level — below the diabetic range, of course — waist size was a better predictor of future diabetes risk in adults who had normal glucose levels, compared with those who had elevated A1C in the range of prediabetes.
The second phase of the study involved 1,537 adults who didn’t have diabetes at the second exam, who had a third follow-up exam (also a median of five years later) at which 122 of them were found to have diabetes. Once again, waist circumference was a better predictor of developing diabetes than A1C in people with normal glucose levels — as was a person’s BMI or amount of visceral (abdominal) fat tissue. But in participants with prediabetes, A1C was a better predictor of future diabetes risk than waist size.
The researchers concluded that looking at multiple measures of body fat — including waist size and the amount of abdominal fat — could be an important way to help predict future diabetes in Black adults, and that more studies should be done to eventually reach specific screening recommendations.