JAMA Study Finds Half of U.S. Adults Have Diabetes or Prediabetes

September 18, 2015 10:51 am Chris Crawford

There's no question that diabetes is a major cause of morbidity and mortality in the United States; in 2012, the disease cost the nation an estimated $245 billion in increased use of health resources and lost productivity.

[STOP DIABETES wordcloud in black and red]

Recently, researchers set out to quantify just how prevalent the disease and its precursor are among American adults. In a large population-based study(jama.jamanetwork.com) published Sept. 8 in JAMA: the Journal of the American Medical Association, authors examined the prevalence of diabetes and prediabetes and related disease trends in U.S. adults from 1988-2012.

One of the most startling findings in this study was that in 2012, more than half of American adults had either diabetes or prediabetes. Also of interest was the fact that more than one-third of those who met the study's criteria for diabetes were unaware they had the disease.

Breakdown of Study Methods

The study used data collected as part of the 1988-94 and the 1999-2000 to 2011-12 National Health and Nutrition Examination Surveys (NHANES), which are designed to be nationally representative of the civilian, noninstitutionalized U.S. population. Specifically, researchers used data from 2,781 adults from 2011-12 to estimate recent prevalence and an additional 23,634 adults from all NHANES conducted between 1988 and 2010 to estimate trends.

Story highlights
  • A study published Sept. 8 in JAMA: the Journal of the American Medical Association found that in 2012, about half of American adults had either diabetes or prediabetes.
  • More than 36 percent of those who met the study's criteria for diabetes were unaware they had the disease.
  • Diabetes rates increased from 9.8 percent in 1988-94 to 12.4 percent in 2011-12 across all age, racial and ethnic groups; in both genders; and by all education and income levels.

Furthermore, the researchers used two definitions of undiagnosed and total diabetes to bolster the reliability of their results. The first of these defined undiagnosed diabetes as any participant who had

  • a hemoglobin A1c level of 6.5 percent or greater,
  • a fasting plasma glucose (FPG) level of 126 mg/dL or greater, or
  • a two-hour plasma glucose (2-hour PG) level of 200 mg/dL or greater (i.e., the hemoglobin A1c, FPG or 2-hour PG definition).

Total diabetes was defined as any participant who had either diagnosed diabetes or undiagnosed diabetes according to the hemoglobin A1c, FPG or 2-hour PG definition.

Because 2-hour PG levels were not available for all age groups and for all NHANES years, researchers also used a second definition that defined undiagnosed diabetes as any participant who had

  • a hemoglobin A1c level of 6.5 percent or greater, or
  • an FPG level of 126 mg/dL or greater (i.e., the hemoglobin A1c or FPG definition).

Using this definition, total diabetes was defined as any participant who had either diagnosed diabetes or undiagnosed diabetes according to the hemoglobin A1c or FPG definition.

Similarly, two definitions of prediabetes were used, with the first defined as any participant who did not have diabetes but who did have a hemoglobin A1c level of 5.7 percent to 6.4 percent, an FPG level of 100 mg/dL to 125 mg/dL or a 2-hour PG level of 140 mg/dL to 199 mg/dL. The second defined prediabetes as any participant who did not have diabetes but who did have a hemoglobin A1c level of 5.7 percent to 6.4 percent or an FPG level of 100 mg/dL to 125 mg/dL.

The 2011-12 NHANES data were used to calculate the prevalence of total diabetes, previously diagnosed diabetes and undiagnosed diabetes, as well as the prevalence of prediabetes in the overall population. These data were stratified by age, gender and race/ethnicity, and age ranges were standardized to those for the overall 2011-12 NHANES interview population. The researchers did this for both the hemoglobin A1c, FPG or 2-hour PG definition of diabetes and prediabetes and the hemoglobin A1c or FPG definition of diabetes and prediabetes.

To investigate trends over time, researchers calculated the age-standardized prevalence of total diabetes based on the hemoglobin A1c or FPG definition overall and by age, gender and race/ethnicity, and education and income level. This analysis was repeated using the hemoglobin A1c, FPG, or 2-hour PG diabetes definition for age groups and NHANES years for which all of this information was available.

Key Study Findings

One of the most startling findings was that using the hemoglobin A1c, FPG or 2-hour PG definition, more than half of Americans age 20 or older in 2012 had either diabetes (14.3 percent of total population) or prediabetes (38.0 percent). Also of interest was the fact that more than 36 percent of those who met the study's criteria for diabetes, or an estimated 5 percent of the overall population, were unaware they had the disease.

Researchers found diabetes was more prevalent among Hispanics (22.6 percent of all Hispanic participants), blacks (21.8 percent) and Asians (20.6 percent) compared with whites (11.3 percent). Asian-Americans also had the highest percentage of undiagnosed cases (50.9 percent of total diabetes cases in this group).

Overall, the study found that diabetes rates increased from 9.8 percent of the total U.S. population in 1988-94 to 12.4 percent in 2011-12 across all age and racial/ethnic groups, in both genders, and by all education and income levels.

Family Physicians Critical in Diabetes Fight

Gary Levine, M.D., and Jonathon Firnhaber, M.D., both from the Department of Family Medicine at the Brody School of Medicine at East Carolina University in Greenville, N.C., will lead an AAFP self-assessment module (SAM) working group on diabetes Sept. 19 in Rosemont, Ill. The course fulfills the knowledge assessment portion of the Maintenance of Certification for Family Physicians SAM process, and the Academy will report answers directly to the American Board of Family Medicine on behalf of workshop participants.

Levine told AAFP News that the results of this JAMA study reflect what he sees in his practice: About 50 percent of his adult patients have diabetes.

"It does seem like we are in the midst of a diabetic epidemic, although according to this study, the increase in prevalence over the past 20 years is less than 5 percent," he said. "It's not clear how many patients with prediabetes go on to become diabetic. In my experience, not many do."

Levine said the surge in diabetes appears to be directly tied to the current obesity epidemic in the United States, and he noted that a shift in U.S. demographics attributed to a growing minority population has probably contributed, as well.

So why does adding more minorities to the population lead to a higher overall diabetes rate? Levine said the greater prevalence of diabetes in minority populations could be due to a combination of genetic and social factors specific to each group.

This means family physicians have a serious battle ahead of them, said Levine, and fighting diabetes starts with offering patients some common-sense information. Patients need to stop overeating and start exercising regularly, if they aren't currently. Dietary recommendations should include a call for healthier foods, and physicians need to recommend at least 150 minutes of aerobic exercise per week to their patients.

For patients with a new diagnosis of diabetes, pharmacologic therapy is indicated and should generally include metformin and other oral agents or insulin as indicated by the individual's hemoglobin A1c or level of hyperglycemia, said Levine.

Related AAFP News Coverage
AAFP Champions Role for FPs in Federal Diabetes Program
(7/22/2015)

Intensive Glucose Control Curbs Mortality in Type 1 Diabetes
(1/20/2015)

USPSTF Issues Draft Recommendation on Glucose Screening, Diabetes
Task Force Finds Evidence of Benefit for Adults at Increased Risk

(10/14/2014)


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