SAN FRANCISCO – The U.S. incidence of adult diabetes doubled between 1980 and 2008 but has fallen a bit since then, which may be a sign that the diabetes epidemic is abating, according to Linda S. Geiss a health statistician with the Centers for Disease Control and Prevention.
This potentially good news does not apply to everyone, however. Both the incidence and prevalence of diabetes continue to increase in Hispanics, non-Hispanic blacks, and adults with less than a high school education, Ms. Geiss and her associates reported at the annual scientific session of the American Diabetes Association.
They studied annual data from the 1980-2012 National Health Interview Surveys to identify diabetes trends in U.S. residents aged 20-79 years. The age-adjusted prevalence and incidence of diagnosed diabetes changed little in the 1980s but each doubled between 1990 and 2008, she said.
Linda S. Geiss
During that time period, the U.S. population became older, less white, and better educated, she noted.
The age-adjusted incidence of diabetes increased from approximately 4/1,000 people in 1980 to more than 9/1,000 in 2008 and then declined to less than 8/1,000 in 2012, a statistically insignificant decrease after 2008. The age-adjusted prevalence of diabetes increased from approximately 4/100 people in 1980 to approximately 8/100 in 2008, with a slight increase after that, "although at a slower rate of pace," Ms. Geiss said.
Even when incidence declines, prevalence can continue to rise if the number of deaths among people with diabetes is smaller than the number of new diagnoses.
"Overall and for some subpopulations, incidence and/or prevalence slowed or plateaued around 2008. Some groups slowed earlier in the 2000s," she said. "After a steady 15- to 20-year increase in prevalence and incidence, we are seeing the first signs that the growth may be slowing or abating. However, given the uncertainty about the reasons behind these changes, future trends are uncertain. Given the large burden of diabetes in the United States, we need to sustain efforts to prevent diabetes and its complications," especially among population groups whose incidence and prevalence rates continue to climb.
Throughout the time period studied, the incidence and prevalence of diabetes were lowest among people aged 20-44 years and highest among people aged 65-79 years. For those two age groups, the incidence of diabetes increased throughout the time period. For middle-aged people of 45-64 years, the incidence plateaued in 2002. The prevalence of diabetes plateaued in 2008 for the middle-aged group and in 2003 for the oldest age group.
Incidence rates for men started to exceed those for women around 1997, continued increasing until 2008, and then declined, though not significantly. The incidence for women increased throughout the time period studied. The prevalence of diabetes plateaued for men in 2001 and for women in 2008.
For adults with a high school education, the incidence of diabetes increased until 2008 and then decreased insignificantly. For other educational levels (more than or less than a high school education), the incidence increased throughout the period. The prevalence slowed among people with more than a high school education in 2000, but increased throughout the time period for the other educational levels.
The incidence and prevalence of diabetes were higher among Hispanics and non-Hispanic blacks than among whites between 1997 and 2012. For whites, the incidence increased from approximately 5/1,000 people in 1997 to 8/1,000 in 2008, then decreased insignificantly to 6/1,000 in 2012. The prevalence of diabetes in whites slowed its rate of increase starting in 2005, Ms. Geiss reported.
"With these cross-sectional data, you can’t determine the reasons behind trend changes," she said. The nationally representative data spanning 3 decades give strength to the findings, but the surveys did not include institutionalized residents or people with undiagnosed diabetes. The study could not distinguish trends for type 1 vs. type 2 diabetes.
One physician in the audience asked if the global financial crisis in 2008 may have been a factor in slowing the diabetes epidemic.
Ms. Geiss said she hadn’t considered that possible explanation. Other factors that may have affected the incidence of diabetes include the adoption of hemoglobin A1c (HbA1c) for the diagnosis of diabetes, she speculated. "We know that HbA1c tends to identify fewer people who have hyperglycemia," she said. Also, U.S. obesity rates have not increased since 2003-2004, and a couple of separate studies have reported declining caloric intake by the U.S. population. Each of these factors may be "prominent drivers" of the slowing incidence of diabetes, she said.
Ms. Geiss reported having no financial disclosures.