Estimates of Diabetic Retinopathy Incidence, Progression Lower Than Previously Reported in American Indians

The incidence and progression of diabetic retinopathy (DR) was found to have lower estimates than had been reported for American Indian and Alaska Native individuals in the past, according to a study published by JAMA Ophthalmology. Extending the time between evaluations for DR for certain patients could be helpful in this case as long as compliance and visual acuity outcomes are not in jeopardy.

The prevalence of diabetes is higher in American Indian and Alaska Native individuals compared with other ethnic groups, with 14.7% of American Indian/Alaska Native individuals having a diagnosis of diabetes, the authors explained. Diabetes is also being diagnosed in this subgroup at younger ages. The prevalence of diabetic eye disease has declined in this subset according to recent studies, but data on incidence of DR are not current and based on older data. This study aimed to estimate the cumulative incidence, incidence rates, and progression of DR in American Indian/Alaska Native patients who are served by the Indian Health Service (IHS) teleophthalmology program.

This study used medical data from routine clinical operations of the IHS teleophthalmology program in 20 states. The teleophthalmology program evaluates patients from the participating primary care clinics and graders identify the clinical levels of DR and diabetic macular edema (DME) severity.

The baseline period for this study was January 1 to December 31, 2015, with a follow-up period of January 1, 2016, to December 31, 2019. Patients were eligible if they had 1 IHS teleophthalmology exam in both periods, were 20 years or older, and had no evidence of DR or mild nonproliferative DR (NPDR) at baseline. Patients were excluded if they had severe NPDR, proliferative DR, and/or had any level of DME.

Severity of DR was assessed through image acquisition. Images from different retinal regions and the optic disc, with the macula and retina, were obtained. Images were graded as having no evidence of DR, mild NPDR, moderate NPDR, severe/very severe NPDR, proliferative DR, or were ungradable. Grading was assessed with the more severely affected eye. Incidence and progression were measured as any increase in level of DR, an occurrence of 2 or more steps, and with the severity level of DR.

There were 8374 patients included in this study, of which 57.0% were women and collectively had a mean (SD) age of 53.2 (12.2) years. The mean time from baseline to follow-up exam was 20.7 (9.5) months. The mean duration of diabetes was 8.6 (7.4) years, with 52.6% of the population managing their diabetes with oral medication alone.

A total of 18.0% of the patients with no evidence of DR at baseline had some level of DR at follow-up; 65.5% of cases were mild NPDR and cumulative incidence of proliferative DR was 0.1%. A total of 6.2% of these patients also had a step increase in DR of 2 or more.

A total of 27.2% of patients with mild NPDR at baseline developed more severe DR after follow-up, with 2.3% experiencing a step increase of 2 or more. Cumulative incidence of severe/very severe NPDR was 0.2% and proliferative DR was 2.2%.

Longer diabetes duration of more than 15 years with DR (risk ratio [RR], 2.0; 95% CI, 1.7-2.4), higher hemoglobin A1C level (any DR: RR, 1.1; 95% CI, 1.1-1.2), and diabetes therapy (any DR: RR, 2.2; 95% CI, 1.6-3.0) were all associated with DR incidence and occurrence of a step increase of 2 or more. Longer duration of diabetes of more than 15 years (RR, 1.8; 95% CI, 1.2-2.5), higher hemoglobin A1C levels (RR, 1.1; 95% CI, 1.0-1.1), and presence of peripheral neuropathy (RR, 1.5; 95% CI, 1.2-2.0) were associated with progression from mild NPDR.

A total of 36.9% of American Indian and Alaska Native patients who had been diagnosed with diabetes before the age of 30 years and taking insulin alone or with oral medications developed DR within 4 years. A total of 28.5% of American Indian and Alaska Native patients diagnosed with diabetes at 30 years or older and taking insulin developed new DR.

The authors noted that this study focused on DR and omitted DME, which could have underestimated the burden of diabetic eye disease incidence. Another limitation was that the follow-up rate is lower than other studies at only 61.2%.

The researchers concluded that the incidence and progression of DR in American Indian and Alaska Native individuals was lower than it was 30 years prior, making it more in line with other populations.

Reference

Fonda SJ, Bursell S-E, Lewis DG, Clary D, Shahon D, Cavallerano J. Incidence and progression of diabetic retinopathy in American Indian and Alaska Native individuals served by the Indian Health Service, 2015-2019. JAMA Ophthalmol. Published online March 9, 2023. doi:10.1001/jamaophthalmol.2023.0167