The prevalence of diabetes in the United States was 12% to 14% in 2011-2012 with higher rates in black, Asian, and Hispanic populations.

Over the past decade, the prevalence of diabetes has increased, placing it as a major cause of mortality and morbidity in the United States.

Andy Menke, Ph.D., of Social & Scientific Systems, a biotechnology company in Silver Spring, Md., and his colleagues sought to estimate the U.S. trends and prevalence of prediabetes, total diabetes, diagnosed diabetes, and undiagnosed diabetes using data from the National Health and Nutrition Examination Survey (NHANES). Their results were published in the Journal of the American Medical Association online Sept. 8.

NHANES is a cross-sectional survey, conducted from 1988 to 1994 and 1999 to 2012. To estimate the most recent prevalence, the investigators sampled 2,781 adults from the 2011-2012 data and included 23,634 adults to estimate the trends from 1988 to 2010.

The prevalence of diabetes was determined based on a diagnosis of diabetes or evidence of based on fasting plasma glucose greater than 126 mg/dL, hemoglobin A1c of 6.5% or more, or 2-hour post prandial glucose greater than 200 mg/dL. Prediabetes was noted to be based on 2-hour post prandial glucose of 140-199 mg/dL, fasting plasma glucose of 100-125 mg/dL, or hemoglobin A1c of 5.7%-6.4%.

During 2011-2012, the prevalence of diabetes based on 2-hour post prandial glucose, fasting plasma glucose, or hemoglobin A1c was 14.3% for total diabetes (diagnosed and undiagnosed). Furthermore, the prevalence was 9.1% for diagnosed, 5.2% for undiagnosed, and 38% for prediabetes.

When compared to white individuals (11.3%), the age-standardized prevalence of diabetes was higher in Hispanic (22.6%, P less than .001), Asian (20.6%, P = .007), and black (21.8%, P less than .001) individuals. Likewise, Hispanics (29.7%, P = .003) and blacks (30.8%, P less than .001) tended to have higher BMIs compared to whites (28.4%). Asians tended to have lower BMIs (24.6%, P less than .001).

The age-standardized prevalence of undiagnosed diabetes was higher in Hispanic (49%, P = .02) and Asian (50.9%, P = .004) individuals than in other groups. However, the age-standardized prevalence of prediabetes was higher in blacks (39.6%) than in Asians (32.2%, P = .05).

When defining diabetes based on hemoglobin A1c or fasting plasma glucose alone, the authors found fewer people with undiagnosed diabetes. For example, the prevalence was 12.3% for total diabetes with 3.1% undiagnosed and 9.2% diagnosed. Furthermore, 36.5% of the study subjects qualified as prediabetic based on these definitions.

The age-standardized prevalance of diabetes increased from 9.8% to 12.4% during the 1988-1994 and 2011-2012 periods (P less than .001 trend). However, there was not much change in prevalence from 2007-2008 to 2011-2012 (12.5% to 12.4%).

The prevalence of diabetes significantly increased during the study time period in both sexes, all racial groups, education levels, incomes, and ages.

The amount of total diabetes that was undiagnosed decreased in most groups, including sex, racial groups, and most age groups. However, in Mexican American subjects the rate of undiagnosed diabetes actually increased over the study period (5.6% to 5.9%, P = .01). The increased prevalence of diabetes was due to increases in the amount of diagnosed diabetes, the authors wrote.

Finally, the age-standardized prevalence of total diabetes for subjects aged 40-74 years was 15.9%, 18.1%, and 18% during 1988-1994, 2005-2006, and 2011-2012, respectively (P = .01 for trend).

“Between 1988-1994 and 2011-2012, the prevalence of diabetes increased significantly among the overall population and among each age group, both sexes, every racial/ethnic group, every education level, and every income level, with a particularly rapid increase among non-Hispanic black and Mexican American participants. The proportion of people who had undiagnosed diabetes significantly decreased,” the authors noted.

The authors further clarified that the lower rates of undiagnosed diabetes over time may be secondary to improved survival in patients with diabetes and better screening.

The National Institute of Diabetes and Digestive and Kidney Diseases supported the study. The authors reported no conflicts of interests.