About half of U.S. adults are still diabetic or “pre-diabetic,” according to a new JAMA report, but the number has held relatively steady over the past half decade.
An estimated 12.4% of adults had diabetes in 2011-12, the time period covered by the most recent survey. That's up slightly from 2009-10 but still a tenth of a percentage point below the peak of 12.5% of adults with diabetes registered in 2007-08.
The authors of an accompanying editorial noted similar plateaus in obesity levels. They suggested the data offered “a glimmer of hope” that numerous interventions to combat diabetes and obesity were paying off.
They included numerous warnings and recommendations by the U.S. surgeon general and the National Academy of Medicine; recent upgrades to food, nutrition, agricultural and physical activity policies; and additional regulation by federal, state and local governments on food choices. "The focus on individual behavioral change related to diet and physical activity by the CDC has begun to affect the prevalence of obesity, and secondarily, after a delay of approximately 10 years, the prevalence of Type 2 diabetes,” wrote University of Michigan Health System internists Drs. William Herman and Amy Rothberg.
The diabetes epidemic cost the nation about $245 billion in medical expenses and lost productivity in 2012.
Overall, the prevalence of diabetes was estimated to be between 12% and 14% while the percentage of U.S. adults considered pre-diabetic was estimated at between 37% and 38%. Researchers surveyed data from 2,781 adults who participated in the 2011-12 National Health and Nutrition Examination Survey by the CDC.
A significant portion of the diabetics identified in the survey had not previously been diagnosed with the disease. “One in three people with diabetes in the U.S. were undiagnosed, which is an indication that there should be greater testing for diabetes,” said lead author Andy Menke, an epidemiologist with Silver Spring, Md.-based Social & Scientific Systems.
Among ethnic groups, the percentage of undiagnosed cases was the highest among Asians and Hispanics. The authors speculated that the undiagnosed rates for Asians may be higher because they had the lowest body mass index among the different ethnic groups and therefore may be screened less frequently for diabetes.
“We were surprised to find that the prevalence of diabetes is relatively high among Asians with 1 in 5 having it despite having a lower BMI than other race/ethnicity groups in the U.S.,” said Menke who collaborated on the report with researchers from the Centers for Disease Control and Prevention and the National Institutes of Health. “Half of Asians with diabetes were undiagnosed. Physicians should remain cognizant that Asians have a higher risk of diabetes at a given BMI and should be screened for diabetes at a lower BMI threshold.”
A larger percentage of Hispanics in the study lacked health insurance, and the authors speculated that resulted in lower access to healthcare and less frequent screening.
The prevalence of diabetes goes up as income goes down. "We found that the lowest income category had more than double the diabetes prevalence of the highest-income category,” Menke said. “It's not clear why there is such a strong association between socio-economic status and diabetes, but it may have to do with access to healthcare, access to healthy foods, or other neighborhood or environmental factors.”
Prediabetes was defined as having a hemoglobin A1c, or blood-sugar, level of 5.7 to 6.4 with 6.5 considered diabetic. The prevalence of prediabetes was more than 30% across both sexes and all racial and ethnic categories. Prediabetes was highest among African-Americans with nearly 40% at risk of developing full-blown diabetes.
“Prediabetes is a condition where blood sugar is higher than normal, but not high enough to be defined as diabetes,” Menke explained. “Prediabetes is generally not considered a clinical entity, but rather a state of being at high risk for diabetes. However, people with prediabetes are also at an increased risk for cardiovascular disease compared to those with normal glucose levels. People with prediabetes can delay or prevent the development of Type 2 diabetes with modest lifestyle changes to lose weight.”
Dr. William Dietz, with George Washington University's Milken Institute of School of Public Health in Washington, noted that being prediabetic puts a person at risk for being in ill health and reflects susceptibility to diabetes. But it doesn't necessarily mean they are presently in ill health.
“Some people call it 'diabetes without developing full-blown symptoms' or 'early diabetes,' but those terms are inaccurate,” said Dietz, who did not participate in the JAMA study. “We know everyone with prediabetes doesn't develop full diabetes and to call it 'early diabetes' infers that people are already there.”
The authors of the JAMA report compared the 2011-12 data with figures from similar surveys conducted between 1988 and 1994 and 2007 and 2008. Diabetes was prevalent in about 3.5% of the population in 1990 and jumped to 7.9% in 2008 before leveling off at its current rate. Prevalence of prediabetes was around 29% between 1999 and 2002 and increased to 36% in surveys done between 2007 and 2010.
The authors noted that progress has been made, but further improvement will depend on sustained and expanded efforts. “Obesity in the U.S. seems to be leveling off, which may slow or stop the increase in diabetes,” Menke said. “But it was not clear if that trend was something we saw based on chance—who happened to be sampled those years—or an indication of a real inflection point marking a change in the trajectory of diabetes prevalence in the U.S.”