African-Caribbean Ethnicity Linked to Greater Risk of Diabetic Retinopathy in T1D

Janaka Karalliedde, MBBS, PhD

Credit: EASD

People with type 1 diabetes (T1D) of African Caribbean ethnicity experience a significantly higher risk of developing sight-threatening diabetic retinopathy (STDR), according to new research.¹

Results from a contemporary longitudinal study of an ethnically diverse cohort of nearly 2,000 people with T1D revealed those of African-Caribbean ethnicity had 39% greater risk of developing STDR compared with non-African Caribbean people, independent of traditional risk factors.

“A large number of people with T1D are at risk for progression to STDR, with significant heterogeneity in the rates and risks of progression,” wrote the investigative team. “Studies such as ours in a distinctive urban cohort of ethnically diverse people with T1D can help identify new risk factors that aid risk stratification and better identify people at high risk of STDR.”

The team, led by Janaka Karalliedde, MBBS, PhD, King’s Health Partners and School of Cardiovascular Medicine & Sciences, King’s College London, suggested a “paucity of knowledge” surrounding the association between ethnicity and progression of DR to STDR in people with T1D. To investigative further, Karalliedde and colleagues analyzed baseline and long-term follow-up data in 1,876 people (median age, 29 years) with T1D undergoing routine examination for diabetic eye diseases in South London between 2004 - 2018. The cohort included 72.1% Caucasian patients, 17.3% African Caribbean patients, 2.9% Asian patients, and 7.6% reported as other races and ethnicities.

Diagnoses of T1D were extracted from eye screening and primary care records and investigators measured socioeconomic status using the Index of Multiple Deprivation (IMD), with a score of 1 indicating the highest level of deprivation and 10 the most affluent. As per the UK National Diabetic Eye Screening criteria, the primary study endpoint was the onset of STDR from baseline retinopathy grade R0 (no retinopathy) and maculopathy grade M0 to grade R2 (pre-proliferative retinopathy) or grade R3 (proliferative retinopathy) and/or the onset of grade M1. In those individuals who developed the primary end point of STDR between the baseline eye screening and follow-up eye screening, the time between those two screening events was used as the time taken for the primary end point to occur.

Upon analysis, 359 (19%) participants developed STDR at the end point, while 1,442 did not over the duration of follow-up. Data showed duration of diabetes, total cholesterol, systolic blood pressure (SBP), and HbA1c were higher in those with progression to STDR, while those of African Caribbean origin were additionally more likely to progress to STDR.

Of participants who reached the end point of STDR during follow-up, 66 developed R2, 293 developed maculopathy grade M1, and 27 (7.5%) developed R2 or R3 and M1. Data showed people of African Caribbean origin compared with non-African Caribbean people had a nearly two-fold higher risk of onset of ≥R2 (9.7% vs. 4.2%), with similar rates for the onset of M1 (21% vs. 15%, respectively).

Multivariable Cox regression models additionally revealed African Caribbean ethnicity (hazard ratio [HR], 1.39; 95% CI, 1.09 – 1.78; P = .009), baseline SBP (HR, 1.01; 95% CI, 1.00 - 1.01; P = .033), and baseline HbA1c (HR, 1.01; 95% CI, 1.00 - 1.01; P = .0001) as significant independent risk factors for progression to STDR. Karalliedde and colleagues noted the 39% greater risk of developing STDR in those of African-Caribbean ethnicity was independent of conventional risk factors for retinopathy, including baseline HbA1c or SBP.

They also indicated the mechanisms that explain the results of increased risk in those of African Caribbean descent requires further investigation, as the study was not designed to explain its cause. Karalliedde and colleagues suggested reasons could include a genetic predisporiton to STDR or a negative “legacy” of poor glycemic control.

“Further research is required to better understand pathophysiology that may explain the association between African-Caribbean ethnicity and higher risk of progression to STDR in people with type 1 diabetes,” investigators wrote.

References

1. Anastasios Mangelis, Piyumi Wijewickrama, Abbeyramei Nirmalakumaran, Nikolaos Fountoulakis, Prashanth Vas, Laura Webster, Samantha Mann, Julian Collins, David Hopkins, Stephen Thomas, Salma Ayis, Janaka Karalliedde; People With Type 1 Diabetes of African Caribbean Ethnicity Are at Increased Risk of Developing Sight-Threatening Diabetic Retinopathy. Diabetes Care 2023; dc222118. https://doi.org/10.2337/dc22-2118