African Caribbean Ethnicity Linked to Sight-threatening Diabetic Retinopathy

African Caribbean ethnicity is associated with a higher risk for sight-threatening diabetic retinopathy (STDR) in individuals with type 1 diabetes, according to study results published in Diabetes Care.

Researchers collected clinical and demographic data from 1876 individuals (50% women) diagnosed with type 1 diabetes between 2004 and 2018. Individuals with no baseline evidence of retinopathy in either eye were included. Data were from electronic medical records and the South East London Diabetes Eye Screening Program. Demographic variables included baseline characteristics, blood pressure, serum creatinine, urine albumin-to-creatinine ratio, HbA_1c level, total cholesterol level, and triglyceride levels. 

The researchers followed the UK National Diabetes Eye Screening Committee (UK NSC) guidelines for retinopathy grading. According to UK NSC guidelines, retinopathy was classified as no retinopathy (R0), background retinopathy (R1), pre-proliferative retinopathy (R2), and proliferative retinoathy (R3); the presence of maculopathy was noted as M1. Two digital fundus photographs were taken per eye for each participant. The median follow-up was 6 years. Variables were compared using one-way ANOVA or Wilcoxon rank sum tests and c² tests. A multivariable Cox regression model was used to calculate hazard ratios.

Among the study participants, 17.3% were of African Caribbean ethnicity, 72.1% were Caucasian, 2.9% were Asian, and 7.6% were classified as other. The median (IQR) age and duration of diabetes in this cohort was 29 (21, 41) years, and  6 (2, 12) years, respectively. The median age of diabetes diagnosis was 19 (11, 30). 

The researchers found that 19% (n=359) of individuals experienced STDR during follow-up. A greater risk for progression to STDR was associated with longer duration of diabetes, higher total cholesterol level, higher systolic blood pressure (SBP), higher HbA_1c level, and lower estimated glomerular filtration rate (eGFR). Specifically, baseline SBP (HR, 1.01; 95% CI, 1.00-1.0; P =.033) and baseline HbA_1c (HR, 1.01; 95% CI, 1.00-1.0; P =.0001) were identified as independent risk factors for STDR progression. 

Individuals of African Caribbean ethnicity also had a higher likelihood of progression to STDR (HR, 1.39; 95% CI, 1.09-1.79; P <.009). Additionally, they had a higher risk for more severe retinopathy when compared with non-African Caribbean participants. The researchers reported a two-fold higher risk for achieving R2 status or greater (9.7% vs 4.2) and significantly higher M1 onset (21% vs 15%). 

Limitations of the study include a lack of information on medication and smoking status, which is a confounding factor for vascular complications of diabetes. Type 1 diabetes was confirmed with medical records only and not with a formal laboratory diagnosis. 

The study authors conclude, “[W]e observed in a multiethnic cohort of people with type 1 diabetes managed in a publically funded health care system the novel finding of African Caribbean ethnicity as an independent predictor of STDR.”