Despite Advances, Decades-Old Racial Disparities Persist in Glycemic Control in the US

A person checking their blood sugar levels with a health care provider

Despite advances in care and pushes for more equitable access to care, a new study suggests racial disparities in glycemic control and severe hyperglycemia among people with diabetes in the US have worsened over the last 3 decades.

An analysis of data from the National Health and Nutrition Examination Survey (NHANES), results of the Johns Hopkins-led study indicate the portion of patients with diabetes who received insulin and achieved glycemic control did not change over the study period, but racial disparities in both of these that existed in 1988 persisted or increased through 2020, particularly among Mexican American individuals.

“Few population-based studies have examined glycemic control among patients using insulin,” wrote investigators. “Previous work showed that the prevalence of glycemic control did not change among US adults with diabetes using insulin from 1988 to 2012, averaging 33% throughout the study period. Our updated results, based on nationally representative data collected from 1988 to 2020, extend this work and show that glycemic control continued to stagnate among insulin users. Our results also establish that the prevalence of severe hyperglycemia did not decrease over time.”

For decades, affordability of insulin and the importance of glycemic control have been at the forefront of diabetes management. In the US and other areas across the globe, systemic inequities have resulted in reduced access to many therapies for minority and other underserved populations. A team from Johns Hopkins University School of Medicine undertook the current research endeavor with the intent of exploring trends and disparities in glycemic control and severe hyperglycemia in adults with diabetes using insulin in the US.

With this in mind, investigators designed their analyses as a serial population-based, cross-sectional study of data recorded in survey cycles of NHANES from 1998-1994 and from 1999-2020. Limiting their analyses to non-pregnant US adults aged 20 years or older with a diagnosis of diabetes and reporting current insulin use, investigators identified 2482 individuals for inclusion in their analyses. This cohort had a manage of 59.8 (SD, 0.4) years, 51.3% were men, 7.0% were Mexican American individuals, 17.9% were non-Hispanic Black individuals, and 65.2% were non-Hispanic White individuals. From the periods ranging from 1988-1994, 1999-2004, 2005-2012, and 2013-2020, investigators obtained data from 475, 388, 755, and 864 individuals, respectively.

The primary outcomes of interest for the study were trends in glycemic control and severe hyperglycemia overall and among subgroups stratified by age, race and ethnicity, and indicators of socioeconomic status. Investigators noted these were assessed using logistic regression. For the purpose of analysis, glycemic control was defined as an HbA1c less than 7% and severe hyperglycemia was defined as an HbA1c level greater than 10%.

Upon analysis, results indicated the portion of patients with diabetes who received insulin and achieved glycemic control did not significantly change from 1988-1994 to 2013-2020, with rates of 29.2% (95% CI, 22.6-36.8) and 27.5% (95% CI, 21.7-34.2), respectively, during those periods (P=.87 for trend). Similarly, there was no significant change in the rate of severe hypoglycemia, with rates of 18.2% (95% CI, 13.0-24.8%) in the period lasting from 1998-1994 to 14.6% (95% CI, 12.0-17.5) from 2013-2020 (P=.28 for trend).

Further analysis indicated trends in glycemic control were consistent across subgroups with the exception of race and ethnicity. Specifically, rates of control decreased significantly for Mexican American adults using insulin from 25.1% (95% CI, 17.2-35.1) in 1988-1994 to 9.9% (95% CI, 5.4-17.4) in 2013-2020 (P=.004 for trend). Among the other various findings from their study, investigators highlighted the prevalence of severe hyperglycemia was roughly twice as high for Mexican Americans (23.9% [95% CI, 13.6-38.7]) and non-Hispanic Black adults (22.7% [95% CI, 17.4-29.0) than it was for non-Hispanic White adults (9.1% [95% CI, 6.0-13.7]) in 2013-2020.

“This serial cross-sectional study of NHANES data from 1988 to 2020 demonstrated that despite advancements in insulin formulations and diabetes management strategies, glycemic control and severe hyperglycemia among adults using insulin did not improve in the general US adult population with diabetes,” investigators concluded. “Racial and ethnic disparities in glycemic control among adults with type 2 diabetes persisted and increased. Current rates of glycemic control in minority groups, especially Mexican American individuals, remain unacceptably low.”

This study, “Trends and Disparities in Glycemic Control and Severe Hyperglycemia Among US Adults With Diabetes Using Insulin, 1988-2020,” was published in JAMA Network Open.

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