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Glycemic Threshold Differs By Ethnicity For Development Of Diabetic Retinopathy

Apr 2, 2019
 
Editor: Joy Pape, MSN, FNP-C, CDE, WOCN, CFCN, FAADE

Author: Ghazal Blair, Pharm.D. Candidate 2019, LECOM School of Pharmacy

Specific A1c, glucose ranges associated with diabetes-specific vision impairment.

Diabetic retinopathy is a condition developed in patients with diabetes as a result of microvascular changes. Capillary leakage and capillary vessel occlusion in the retina are the main adverse changes seen with diabetic retinopathy. Chronic hyperglycemia is the leading reason for these changes, which eventually leads to vision loss. Maximum glycemic management (HbA1c of 6.5% or lower) and blood pressure reduction have been known to be the key to reduce the risk of development of diabetic retinopathy. Additionally, previous studies recommend the use of glycemic threshold as a predictor for diabetes retinopathy.

In a data analysis, the association between hyperglycemia and diabetic retinopathy was re-examined. This study included data for nine trials with a total of 44,623 participants ages 20–79 years old. The investigators assessed the prevalence of different categories of retinopathy (moderate to severe) with different glycemic measurements, including: fasting glucose, 2-hour postprandial glucose, and HbA1C. Results of data analysis showed a curvilinear relationship for fasting glucose and HbA1C and diabetes-specific retinopathy. It was noted that fasting glucose less than 6.0 mmol/l and HbA1C below 6.0% was associated with a lower diabetic retinopathy occurrence. Additionally, the data analysis indicated that diabetes-specific retinopathy was associated with ranges greater than 6.4–6.8 mmol/l for fasting blood glucose, 9.8–10.6 mmol/l for postprandial blood glucose, and 6.3–6.7% for HbA1C.

Another study, published in the Journal of Diabetes Research, was conducted to assess the associations of diabetic retinopathy with fasting plasma glucose (FPG), 2-hour postprandial plasma glucose (2hPG), and HbA1c in a Chinese population. This study included a total of 3,124 participants. Study participants were assessed by retinal photography for diabetic retinopathy. Researchers evaluated the prevalence of diabetic retinopathy based on FPG, 2hPG, and HbA1c. The results showed that the prevalence of DR increased for FPG greater than 7.03 mmol/L and HbA1c greater than 6.4%.

A newly published study proposes that risk of diabetic retinopathy development based on glycemic threshold is variable in different ethnic groups and races. This study was conducted to observe the association between glycemic threshold for retinopathy in different ethnic groups. In this study, researchers evaluated data on 1,215 Hispanics, 1,084 African Americans, and 3,003 Caucasians. Data from 2005 to 2008 was collected from the National Health and Nutrition survey. Amongst all participants included in this study, 661 had indication for diabetic retinopathy based on retinal imaging,

Upon data analysis, it was observed that optimal predictive threshold for HbA1c was 6% for all races. Furthermore, the race-specific optimal Hb1A1c threshold as predictor for diabetes retinopathy is as follows: 6% for Caucasians, 6.5% for African Americans, and 6.4% for Hispanics.

Although this study reveals that glycemic threshold for diabetic retinopathy varies by race, there are more prospective trials needed to further evaluate these results. Future studies should be designed to assess sociodemographic variables and how these influence the risk of diabetic retinopathy and glycemic thresholds.

Practice Pearls:

  • Incidence of blindness caused by diabetic retinopathy is rising, despite effective treatments.
  • Duration of diabetes is the most important risk factor for retinopathy.
  • Diverse ethnic groups may have a different glycemic threshold in regards to developing diabetic retinopathy.

 

References:

Glycemic Thresholds for Diabetes-Specific Retinopathy. Stephen Colagiuri, Crystal M.Y. Lee, Tien Y. Wong, Beverley Balkau, Jonathan E.Shaw, Knut Borch-Johnsen, the DETECT-2 Collaboration Writing Group Diabetes Care Jan 2011, 34 (1) 145-150; DOI: 10.2337/dc10-1206

Rui Zhang, Yufeng Li, Simin Zhang, Xiaoling Cai, Xianghai Zhou, and Linong Ji, “The Association of Retinopathy and Plasma Glucose and HbA1c: A Validation of Diabetes Diagnostic Criteria in a Chinese Population,” Journal of Diabetes Research, vol. 2016, Article ID 4034129, 7 pages, 2016. https://doi.org/10.1155/2016/4034129.

Chatziralli, Irini P. “The Role of Glycemic Control and Variability in Diabetic Retinopathy” Diabetes therapy : research, treatment and education of diabetes and related disorders vol. 9,1 (2017): 431-434.

Ghazal Blair, Pharm.D. Candidate 2019, LECOM School of Pharmacy