Miriam E. Tucker
May 30, 2019
Rates of diagnosed diabetes in the United States may finally be declining but overall numbers remain high, new findings suggest.
The analysis of data for an almost 40-year period (1980-2017) from the National Health Interview Survey (NHIS) was published online May 28 in BMJ Open Diabetes Research and Care by Stephen R. Benoit, MD, and colleagues from the Division of Diabetes Translation, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia.
After nearly a two-decade increase in both prevalence and incidence of diagnosed diabetes in the United States, the prevalence — the number of people living with diagnosed diabetes — has stabilized for the past 8 years and there has been a decrease in incidence, driven mostly by that seen among non-Hispanic whites.
This reduction means new cases declined by 35% from 2008 to 2017, a sign, perhaps, that efforts to stop the nation's diabetes epidemic are working, say the researchers.
However, they caution, "Causes of the plateauing of prevalence and decrease in incidence are unclear and although the trends are encouraging, the overall burden of diabetes remains high and warrants continued intervention and monitoring."
In a press release, Ann Albright, PhD, director of the Division of Diabetes Translation at the CDC, said: "The findings suggest that our work to stem the tide of type 2 diabetes may be working — but we still have a very long way to go."
"We must continue proven interventions and deploy innovative strategies if we're going to see a continued decline in type 2 diabetes among Americans," she urged.
Diabetes Prevalence: Unchanged Since 2009
Benoit and colleagues calculated annual prevalence and incidence of self-reported diagnosed diabetes (types 1 and 2 combined) for adults aged 18-79 years using the annual, nationally representative cross-sectional NHIS data for the 37-year period. Trends in rates by age group, sex, race/ethnicity, and education were assessed using annual percentage change (APC). All values were age-adjusted.
The overall prevalence of diagnosed diabetes didn't significantly change from 1980 to 1990 (3.5 vs 3.4 per 100 adults; P = .50). But after that, it rose significantly by about 4.4% per year from 1990 to 2009, peaking at 8.2 per 100 adults (P < .001).
Then it plateaued, with an APC of just –0.3% (P = .53) through 2017, at 8.0 per 100 adults, representing about 21 million adults in total.
Prevalence trends were similar across demographic groups, except for a 1.1% increase in APC from 2005 to 2017 among adults with more than a high school education (P = .005).
While those with a high school education or less experienced a similar plateau to the population in general, their overall prevalence of diagnosed diabetes remained approximately double that of people with more than a high school education.
Diabetes Incidence: Dropping Since 2007
The overall incidence of diagnosed diabetes didn't change from 1980 to 1990 (3.6 vs 3.1 per 1000 adults; P = .97). After that, it increased significantly, with an annual percentage change of 4.8% (P < .001), from 1990 to 2007, peaking at 7.8 per 1000 adults.
Thereafter it began dropping significantly, at an APC of –3.1% (P < .001) down to 6.0 per 1000 adults in 2017. This corresponded to a drop from about 1.73 million cases per year of diabetes in 2008 to 1.34 million cases per year in 2017.
Significant trends among subgroups included a decline among non-Hispanic whites in 2008-2017, with an APC of –5.1% (P = .002), and an increase among adult Hispanics with more than a high school education in 1999-2017, with an APC of 4.2% (P = .02).
What's Behind the Changes?
The specific cause for the large decrease in diabetes incidence can't be determined from these data, Benoit and colleagues note.
Trends in several type 2 diabetes risk factors, including intake of added sugar, sugar sweetened beverages, total calories, and physical inactivity, peaked in the mid-2000s and plateaued or decreased thereafter. However, causal inferences can't be made, they say.
Moreover, they point out, "obesity and severe obesity trends have increased over the past 10 years and prediabetes remains unchanged and high, affecting 84 million US adults, or 34% of the US adult population."
Changes in American Diabetes Association recommendations for the screening and diagnosis of diabetes may have also had an effect, including the lowering of the fasting glucose threshold for diagnosing diabetes in 1997, and the 2010 recommendation for use of HbA1c, a less sensitive indicator than glucose.
"Although an encouraging sign of success, due to the persistence of major risk factors such as obesity and prediabetes, we caution that trends are likely affected by changing awareness, detection, and diagnostic practices," Benoit and colleague write.
Extended lifespans of people diagnosed with diabetes likely contributed to the lack of reduction in prevalence, they add.
"Even in the event of true reductions in incidence, the high prevalence and declining mortality signifies a continued high overall burden of diabetes," they stress.
"For these reasons, we urge a continued emphasis on multilevel multidisciplinary prevention to reduce both type 2 diabetes and diabetes complications," they conclude.
The authors are all employees of the CDC and had no disclosures.