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Invited Commentary
Diabetes and Endocrinology
September 7, 2018

Racial Differences in Trajectories of Hemoglobin A1c: Further Evidence of Gaps in Care

Author Affiliations
  • 1Jaeb Center for Health Research, Tampa, Florida
JAMA Netw Open. 2018;1(5):e181882. doi:10.1001/jamanetworkopen.2018.1882

Despite the known risks of elevated hemoglobin A1c (HbA1c) levels on diabetes-related complications, only a third of youth younger than 18 years achieve the HbA1c target of less than 7.5% of total hemoglobin (to convert to proportion of total hemoglobin, multiply by 0.01) set forth by the American Diabetes Association and the International Society for Pediatric and Adolescent Diabetes.1 Racial disparities in diabetes management and glycemic outcomes remain one of many barriers to achieving glycemic targets in youth with type 1 diabetes (T1D). Kahkoska and colleagues2 assessed whether the pattern of glycemic control over time differed by race and ethnicity among 1313 youths with T1D participating in the SEARCH for Diabetes in Youth study. Participants were followed up for an average of 9 years. Group-based trajectory modeling was performed to classify participants into HbA1c trajectories and assess the association with race and ethnicity. Three trajectories were identified: low baseline HbA1c with mild increases over time; moderate baseline HbA1c with moderate increases over time; and moderate baseline HbA1c with major increases over time. In an overall analysis adjusted for demographic and clinical characteristics, including socioeconomic status, non-Hispanic black youth were substantially more likely to have moderately elevated HbA1c levels at baseline with either moderate or major increases over time compared with non-Hispanic white youth. Hispanic youth were also more likely to have moderately elevated HbA1c levels at baseline with major increases over time compared with non-Hispanic white patients, although the extent of the confidence interval suggests the possibility that this association could be due to chance since there has not been adjustment for multiplicity. When the investigators stratified the analysis by sex and age at diagnosis, the race and ethnicity differences in trajectory membership were only observed in males (not in females) and youth diagnosed before age 9 years.

Previous studies have reported racial differences in HbA1c even after adjustment for socioeconomic status.3-5 In an analysis of 10 704 youths participating in the T1D Exchange clinic registry, Willi and colleagues5 reported a higher mean HbA1c level in non-Hispanic black patients compared with non-Hispanic white patients (9.6% vs 8.4% of total hemoglobin), with a substantial difference present even among those families with annual household income of $100 000 or more (9.1% vs 8.1% of total hemoglobin).3 As in the study by Kahkoska et al,2 comparing Hispanic white patients with non-Hispanic white patients, the difference was small after adjusting for socioeconomic status was considered to be not statistically significant after adjusting for multiple comparisons.

There are a number of possible explanations for the large differences in HbA1c patterns observed between non-Hispanic white youth and non-Hispanic black youth which are discussed by the authors. Some may be actionable and some not. Kahkoska and colleagues2 also note the limitations of the study and the interpretation of the results. There is now clear evidence that on average black patients have a higher HbA1c level than white patients for the same mean glucose concentration as reported in the recent study by Bergenstal and colleagues,6 which found the difference to be on the magnitude of 0.4%. Although this difference is important to recognize particularly when comparing the baseline HbA1c levels between black and white participants, it seems less likely to influence the trajectory of HbA1c levels over time. Furthermore, the magnitude of the observed between-race differences in the study by Kahkoska and colleagues2 is so large that even adjusting for a 0.4% average effect of race on HbA1c measurement would not have any meaningful effect on the conclusions.

Other possible explanations offered by Kahkoska and colleagues2 include differences in social determinants of health, such as family dynamics and health care utilization, or possible biases within the health care system including implicit or perceived clinician bias. These factors are not easily assessed but it is critical that further research is undergone to understand the observed racial disparities to design targeted interventions. The more pronounced racial differences in HbA1c patterns in male youth are an interesting finding that warrants further investigation.

The SEARCH for Diabetes in Youth study was conducted with the primary objective to determine the incidence and prevalence of diabetes in youth. This landmark study not only was successful in fulfilling this objective but has contributed to knowledge about pediatric diabetes broadly in innumerable ways. The study by Kahkoska and colleagues2 further adds to the SEARCH for Diabetes in Youth study’s contributions by providing further insight into existing racial disparities in youth with T1D and it paves the way for the next steps to understanding the major causes of racial disparities in glycemic control.

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Article Information

Published: September 7, 2018. doi:10.1001/jamanetworkopen.2018.1882

Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2018 Miller KM. JAMA Network Open.

Corresponding Author: Kellee M. Miller, PhD, Jaeb Center for Health Research, 15310 Amberly Dr, Ste 350, Tampa, FL 33647 (kmiller@jaeb.org).

Conflict of Interest Disclosures: None reported.

References
1.
Miller  KM, Foster  NC, Beck  RW,  et al; T1D Exchange Clinic Network.  Current state of type 1 diabetes treatment in the U.S.: updated data from the T1D Exchange clinic registry.  Diabetes Care. 2015;38(6):971-978. doi:10.2337/dc15-0078PubMedGoogle ScholarCrossref
2.
Kahkoska  AR, Shay  CM, Crandell  J,  et al.  Association of race and ethnicity with glycemic control and hemoglobin A1c levels in youth with type 1 diabetes.  JAMA Netw Open. 2018;1(5): e181851. doi:10.1001/jamanetworkopen.2018.1851Google Scholar
3.
Kamps  JL, Hempe  JM, Chalew  SA.  Racial disparity in A1C independent of mean blood glucose in children with type 1 diabetes.  Diabetes Care. 2010;33(5):1025-1027. doi:10.2337/dc09-1440PubMedGoogle ScholarCrossref
4.
Petitti  DB, Klingensmith  GJ, Bell  RA,  et al.  Glycemic control in youth with diabetes: the SEARCH for Diabetes in Youth Study.  J Pediatr. 2009;155(5):668-672 e661-663. doi:10.1016/j.jpeds.2009.05.025PubMedGoogle ScholarCrossref
5.
Willi  SM, Miller  KM, DiMeglio  LA,  et al; T1D Exchange Clinic Network.  Racial-ethnic disparities in management and outcomes among children with type 1 diabetes.  Pediatrics. 2015;135(3):424-434. doi:10.1542/peds.2014-1774PubMedGoogle ScholarCrossref
6.
Bergenstal  RM, Gal  RL, Connor  CG,  et al; T1D Exchange Racial Differences Study Group.  Racial differences in the relationship of glucose concentrations and hemoglobin A1c levels.  Ann Intern Med. 2017;167(2):95-102. doi:10.7326/M16-2596PubMedGoogle ScholarCrossref
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