This Physician’s Weekly feature updating the prevalence of diabetes and associated trends was completed in cooperation with the experts at the American Diabetes Association.
According to recent data, diabetes continues to be a major cause of morbidity and mortality in the United States, costing an estimated $245 billion due to greater use of healthcare resources and lost productivity. Recent analysis of the scope of both diagnosed and undiagnosed diabetes in the U.S. gives new perspectives on where the challenges and opportunities lie in changing the course of the disease.
In a recent study published in JAMA, investigators estimated the prevalence of diagnosed diabetes, undiagnosed diabetes, and total diabetes (diagnosed plus undiagnosed populations) using data collected in the 1988-1994 and the 1999-2000 to 2011-2012 National Health and Nutrition Examination Surveys (NHANES).
“Research shows that the prevalence of diagnosed diabetes and undiagnosed diabetes has increased in the U.S. during the past few decades,” says Matt Petersen. “We now have new survey data available to estimate diabetes prevalence and trends, including data on minority populations that we haven’t had before. This information can help clinicians identify areas of unmet need and determine where to dedicate available resources to improve outcomes and enhance quality of life for patients living with the disease.”
For the study, the authors used data from 2,781 adults from NHANES 2011-2012 to estimate the recent prevalence of diabetes and an additional 23,634 adults from 1988-2010 to examine long-term trends. “These data can help healthcare providers examine changes over time and gain a better understanding of current patient demographics,” explains Petersen.
For the analysis, the research team defined diabetes prevalence as a previous diagnosis of diabetes or, if diabetes was not previously diagnosed, by A1C, fasting plasma glucose (FPG) levels, or 2-hour (PG). A1C levels were defined as 6.5% or higher, FPG levels were 126 mg/dL or greater, and 2-hour PG levels were 200 mg/dL or higher. The analysis also includes prevalence data using only A1C and fasting glucose levels, without the 2-hour PG, since the first two tests are the ones most commonly used in the clinical setting.
Using all three tests when analyzing the 2011-2012 NHANES population, the unadjusted prevalence was 9.1% for diagnosed diabetes and 5.2% for undiagnosed diabetes, resulting in a combined rate of 14.3% for total diabetes. Among patients who had diabetes, 36.4% were undiagnosed with the disease. “The percentage of undiagnosed diabetes was around 50% in the mid-1990s and declined for a number of years, but has been stuck stubbornly at around 35% in recent years,” says Petersen.
Researchers also found that the total prevalence of diabetes among white study participants (11.3%) was about half that of blacks (21.8%), Asians (20.6%), and Hispanics (22.6%). The age-standardized percentage of diabetes cases that were undiagnosed was significantly higher for Asians (10.6%) and Hispanics (10.1%) than for non-Hispanic whites (3.8%) or blacks (7.0%). “With this new data, we’re beginning to see the severe impact of diabetes—both diagnosed and undiagnosed—among other racial and ethnic populations,” Petersen says. “These patient groups warrant more attention from clinicians.”
Petersen notes that the JAMA study is among the first to provide detailed national estimates of the prevalence of diabetes among Asians in the U.S. The Asian population was oversampled in NHANES for the first time in 2011-2012. Petersen says more years of oversampling may provide additional information about specific Asian subgroups and trends over time. “This data is also important because Asians may be screened less frequently for diabetes because they often have lower BMIs at a comparable degree of diabetes risk,” he says. Recently, the American Diabetes Association recommended that all Asian American adults presenting with a BMI of 23 kg/m2 or higher be considered for diabetes screening. This BMI cut point is lower than that of other U.S. adults, which is 25 kg/m2 or higher.
Between 1988-1994 and 2011-2012, the prevalence of diabetes increased significantly among the overall U.S. population (Figure). Trends in the prevalence of diabetes also increased among each patient age group, both sexes, and every racial and ethnic group. The study authors noted that prevalence trends also increased in every educational and income level and reported that there were especially rapid diabetes prevalence increases in black and Mexican-American participants.
“Importantly, the JAMA study found that the proportion of people who had undiagnosed diabetes decreased significantly over the study period, which is an encouraging sign,” Petersen says. “However, other data shows that this decline has plateaued, and we should not become complacent. There may be several reasons as to why this occurred. The decline in undiagnosed diabetes may be the result of a combination of better screening for diabetes and better survival among people with diagnosed diabetes.” He adds that similar improvements may not have occurred among Hispanics and younger people with diabetes due to a lower percentage of these people having health insurance, which in turn reduces access to healthcare.
“The prevalence and trends from this study are important to helping clinicians understand and recognize shifting demographics that need to be addressed,” says Petersen. “In the future, it will be important to continue monitoring trends among racial and ethnic minorities, particularly Asian Americans, to enhance efforts aimed at reducing healthcare disparities among vulnerable populations.”
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Cowie CC, Rust KF, Ford ES, et al. Full accounting of diabetes and pre-diabetes in the US population in 1988-1994 and 2005-2006. Diabetes Care. 2009;32:287-294.
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