Analyzing trends on the prevalence of diabetes, prediabetes, and glycemic control is important for healthcare policy and planning. In an effort to update current trends, Elizabeth Selvin, PhD, MPH, and colleagues published a study in Annals of Internal Medicine that analyzed data from more than 43,000 participants. Data were collected over 20 years from the National Health and Nutrition Examination Surveys. The study team calibrated A1C levels across the 20 years of data collection and compared trends in diabetes and prediabetes defined by A1C categories with those defined by fasting glucose levels.

Dramatic Increases

According to findings, approximately 21 million adults in the United States (aged 20 and older) had confirmed diabetes in 2010. “The number of diabetes and prediabetes cases has nearly doubled over the last 20 years, and obesity has been a large part of the blame for these observed increases,” says Dr. Selvin. Diabetes prevalence for the entire population increased from just below 6% to about 10% over the past 2 decades. The estimated prevalence of prediabetes ranges from 12% to 30% of the U.S. population, depending on the definition used.


Previous studies of diabetes prevalence have relied on single tests of glucose to identify undiagnosed diabetes. In practice, however, glucose tests should be confirmed by a second test to make the diagnosis. The study by Dr. Selvin and colleagues used a second measure—A1C—to confirm all cases of undiagnosed diabetes in order to give a more accurate estimate of the burden in the population. An important finding was that the proportion of diabetes cases that are currently undiagnosed has decreased and is now just 11% of total diabetes cases. This suggests that improvements have been made in screening and diagnosis.

Challenges Persist

The study also found that diabetes has affected various types of patient groups disproportionately. “Alarming increases in diabetes were observed among African Americans, Hispanics, and elderly patients,” says Dr. Selvin. Racial and ethnic differences were seen in treatment of diabetes and glycemic control. Among people diagnosed with diabetes who reported currently taking medications, only 52% of non-Hispanic African Americans and 43% of Mexican Americans had A1C levels less than 7.0%, compared with a 57% rate for non-Hispanic whites.

“While we’re doing better with screening and diagnosis, there is still a growing need to recognize the challenges that remain,” Dr. Selvin says. “The disparities we observed in ethnic minorities and older people have increased over the past 20 years. This is especially concerning since these patient groups are also at greater risk for diabetes complications. These results highlight that efforts are needed to encourage weight loss and other lifestyle changes, even if patients are receiving medications to treat their diabetes.”