The US is notorious for its high prevalence of diabetes. However, a current study shows that at least the number of undiagnosed cases could be significantly lower than previously assumed.
Diabetes is considered to be one of the greatest public health burdens worldwide. In the US, it affects about 14% of the US adult population and more than a quarter of those age 65 and older. The prevalence of diabetes has increased in recent decades, due in part to the epidemic of obesity can be traced back – not only in the USA, also in Germany.
High number of unreported cases due to bad criteria?
In its 2020 National Diabetes Statistics Report, the US CDC estimated that approximately 2.8% of the population over the age of 18, or approximately seven million Americans, have undiagnosed diabetes. This would represent about 22% of the total diabetes burden.
The estimates in this report are based on national survey data and a single blood test result that increased a blood glucose level indicates. However, doctors typically diagnose diabetes only after confirming the elevated test result to reduce false positives. Clinical guidelines recommend that an initial elevated result at Standard fasting glucose test through a HbA1c-Test or a second fasting glucose test is confirmed a few weeks later.
“Our results suggest that the actual number is much lower and that overall US providers are doing a good job of diabetic screening and diagnosis,” said Elizabeth Selvin, professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health and Lead author of a study trying to better estimate the prevalence of undiagnosed diabetes.
Fewer undiagnosed cases than expected
In your new study the researchers at the Johns Hopkins Bloomberg School of Public Health applied a similar two-test criterion to blood test results from the CDC’s National Health and Nutrition Examination Surveys. These surveys combine interviews and surveys of nationally representative samples of US adults and have been conducted for several decades. The research team used survey results from a total of 30,492 people over the period 1988-2020.
The researchers considered people in the survey to have “confirmed undiagnosed diabetes” if they did not have a diagnosis of diabetes but their test results showed elevated levels on both fasting blood glucose and HbA1c tests.
The researchers found that the number of people in this category for the most recent dataset (2017-2020) suggests a national prevalence of just 1.23 percent — less than half of the CDC’s most recent estimate based on individual test scores. This would correspond to only about 9.5 percent of the total diabetes prevalence. This more conservative estimate of undiagnosed diabetes prevalence has remained essentially unchanged since 1988.
In contrast, however, the results indicate that the diagnosed diabetes prevalence in the United States has increased sharply, from 4.6% of the population in the 1988-1994 survey period to 11.7% in the 2017-2020 period, accounting for 90.5% of the total diabetes prevalence in the country. The increase in the burden of diabetes in the United States over the past few decades is therefore largely due to the increase in the number of diagnosed cases.
A question of skin color
Even if the providers are doing a good job overall, Selvin criticizes: “Nevertheless, the number of undiagnosed diabetics is still high in some subgroups, which indicates that there is still a long way to go.”
The analysis found that older and obese adults, ethnic minorities (especially Mexican and Asian Americans), and those without access to health care were significantly more likely to go undiagnosed. The estimated prevalence of confirmed undiagnosed diabetes was also high among people who were more than a year old since their last doctor visit.
“It’s really worrying that certain populations are being overlooked by the healthcare system. This is probably a key reason why the number of undiagnosed diabetics in these groups remains high,” says Dr. Michael Fang, an assistant professor in the Department of Epidemiology at the Bloomberg School and first author of the study.
In conclusion, Fang notes, “Traditional methods appear to have captured the vast majority of adults with undiagnosed diabetes.” Populations with undiagnosed diabetes may be harder to reach. “Maybe screening measures aimed at these groups are needed.”
This article is based on a press release from the Johns Hopkins University Bloomberg School of Public Health. We have the original publication for you here and linked in the text.
Image source: John Tyson, unsplash.