Retinopathy develops at similar glucose levels but higher HbA(1c) levels in people with black African ancestry compared to white European ancestry: evidence for the need to individualize HbA(1c) interpretation

• Authors: Lisa Staimez, Emory University; Mary Rhee, Emory University; Y Deng, Emory University; Sandra Safo, Emory University; SM Butler, Emory University; BT Legvold, Emory University; SL Jackson, Centers for Disease Control and Prevention, Atlanta; CN Ford, Emory University; Peter Wilson, Emory University; Qi Long, Emory University; Lawrence Phillips, Emory University
• Journal Title: DIABETIC MEDICINE
• Volume: Volume 37, Number 6
• Publisher: WILEY | 2020-04-25, Pages 1049-1057
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1111/dme.14289
• Subjects: Health Sciences, Public Health; Biology, Biostatistics; Health Sciences, Epidemiology; Health Sciences, Medicine and Surgery; Biology, Bioinformatics
• Keywords: Science & Technology; Life Sciences & Biomedicine; Endocrinology & Metabolism; TELERETINAL IMAGING PROGRAM; DIABETIC-RETINOPATHY; GLYCATED HEMOGLOBIN; ETHNIC-DIFFERENCES; VETERANS; HEALTH; RACE; HYPOGLYCEMIA; PREVENTION; MEDICARE

Abstract

Aims: To examine the association of HbA1c and glucose levels with incident diabetic retinopathy according to black African or white European ancestry. Methods: In this retrospective cohort study of 202 500 US Veterans with diabetes (2000–2014), measures included HbA1c, outpatient random serum/plasma glucose, and incident retinopathy [conversion from negative to ≥2 positive evaluations (ICD-9 codes), without a subsequent negative]. Results: At baseline, the study population had a mean age of 59.3 years, their mean BMI was 31.9 kg/m2, HbA1c level was 57 mmol/mol (7.4%) and glucose level was 8.8 mmol/l, and 77% were of white European ancestry (white individuals) and 21% of black African ancestry (black individuals). HbA1c was 0.3% higher in black vs white individuals (P < 0.001), adjusting for baseline age, sex, BMI, estimated glomerular filtration rate (eGFR), haemoglobin, and average systolic blood pressure and glucose. Over 11 years, incident retinopathy occurred in 9% of black and 7% of white individuals, but black individuals had higher HbA1c, glucose, and systolic blood pressure (all P < 0.001); adjusted for these factors, incident retinopathy was reduced in black vs white individuals (P < 0.001). The population incidence of retinopathy (7%) was associated with higher mean baseline HbA1c in individuals with black vs white ancestry [63 mmol/mol (7.9%) vs 58 mmol/mol (7.5%); P < 0.001)], but with similar baseline glucose levels (9.0 vs 9.0 mmol/l; P = 0.660, all adjusted for baseline age, sex and BMI). Conclusions: Since retinopathy occurs at higher HbA1c levels in black people for a given level of average plasma glucose, strategies may be needed to individualize the interpretation of HbA1c measurements.