Out of Control: Trends in Diabetes and Obesity

Henry R. Black, MD


August 26, 2014

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Hi. I'm Dr. Henry Black, Adjunct Professor of Medicine at the New York University Langone School of Medicine.

Diabetes has become epidemic in the United States. Rates of diabetes and obesity are increasing, especially over the past 30 years. The questions are: Why? How are we diagnosing it, and what, if anything, can we do about it?

In 2010, measurement of hemoglobin A1c (HbA1c) was added to the diagnosis of diabetes. This isn't a big problem because the differences in the ways that laboratories measure HbA1c vary only by 4%-5%. In an individual, that is not going to matter much; but in a population, when you try to estimate the number of people with diabetes, that difference can be enormous.

A recent study[1] looked at national trends from 1988 to 1994, and then again from 1999 to 2010, using HbA1c and fasting glucose measurements from patients in the National Health and Nutrition Examination Survey. The diagnosis of diabetes was self-reported by patients who were told by a doctor or other healthcare provider that they had diabetes. Women with gestational diabetes only were excluded.

Overall, the study included more than 43,000 individuals who were 20 years of age or older and who had HbA1c and fasting glucose levels available. The investigators also looked at anthropometry data, body mass index (BMI), medications, and waist circumferences. They defined undiagnosed diabetes as an HbA1c > 6.5% and prediabetes as an HbA1c of 5.7%-6.4%. Glycemic control was considered an HbA1c of < 7% or < 8%. Confirmed diabetes was a fasting glucose >126 mg/dL with an HbA1c ≥ 6.5%, which they felt was similar to how diabetes would be defined in clinical practice.

Increases in obesity rates were found among Mexican Americans, according to BMI, during a time when overall obesity rates increased from approximately 21% (in 1988-1994) to almost 33% (in 2005 -2010). Using an HbA1c ≥ 6.5%, the total number of people with diabetes increased from about 6% to almost 10% during this period. Adding fasting plasma glucose to the definition raised diabetes rates even more, from about 7% to almost 11%.

Among patients taking medication for diabetes, the number of patients with controlled diabetes (HbA1c levels < 7%) increased from about 40% to more than 55%, and the proportion of patients with undiagnosed diabetes fell from 16% to about 11%.

The total diabetes prevalence in non-Hispanic blacks was about 15% compared with 8.5% in whites and 11.6% in Mexican Americans. Among those who were on medications, the rate of HbA1c levels < 7% (controlled diabetes) increased as well, from about 40% to more than 55%. So, we are doing better in some respects. However, the glycemic control rate in whites was about 57% and was 52% in blacks, but was only 43% in Mexican Americans.

As of 2010, we had about 20.6 million confirmed cases of diabetes in the United States, an increasing problem that can be explained by obesity and demographics. Only 11% of the confirmed cases of diabetes were undiagnosed, and a large burden of undiagnosed diabetes was in older individuals.

As we are considering this, we have to start paying attention to the undertreated group -- Mexican Americans and older patients, in particular -- if we are going to get a handle on this and try to prevent the complications we expect from diabetes. Thank you.


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