Younger Age, Albuminuria Linked to Advanced Diabetic Retinopathy in South India

India has a 10% prevalence of type 2 diabetes, the second largest in the world, and South India is particularly affected by diabetes-related complications, including diabetic retinopathy (DR).

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To examine risk factors for DR and its subtypes, including those that might be population-specific, researchers at Mass Eye and Ear/Massachusetts General Hospital participated in the cross-sectional South Indian Genetics of Diabetic Retinopathy (SIGNATR) Study, which gathered data on demographic, clinical and genetic risk factors.

Lucia Sobrin, MD, MPH, associate chief of Clinical Data Science and director of the Morse Laser Center at Mass Eye and Ear, and co-principal investigators Sudha Iyengar, PhD, from Case Western University, and Sinnakaruppan Mathavan, PhD, from Sankara Nethralaya, and their respective teams, report in Current Eye Research that younger age and albuminuria are among the key, non-genetic risk factors for DR in South India.

Methods

The researchers prospectively enrolled 3,060 patients at a hospital, a community ophthalmic center, and temporary outreach clinics in urban and rural areas. They also visited home-bound individuals who had participated in an earlier study of DR.

Unique among epidemiologic studies of DR, at the hospital the team performed dilated ultrawide-field fundus imaging and used optical coherence tomography (OCT) to characterize diabetic macular edema. Outside the hospital, participants underwent non-mydriatic fundus photography and no OCT.

Images of 2,941 participants (56% male, mean age 58) were suitable for grading DR severity.

Results

In multivariate regression analyses, the significant risk factors were:

Proliferative DR

• Younger age—OR, 0.95 per year
• Male sex—OR, 1.91
• Longer duration of diabetes—OR, 1.10 per year
• Higher hemoglobin A1c—OR, 1.13 per percentage point
• Increased high-density lipoprotein cholesterol—OR, 1.02 per mg/dL
• Albuminuria—OR, 5.84

Clinically significant macular edema

• Younger age—OR, 0.98
• Male sex—OR, 1.59
• Longer duration of diabetes—OR, 1.06
• Higher HbA1c—OR, 1.12
• Albuminuria—OR, 3.90

Center-involved diabetic macular edema

• Younger age—OR, 0.97
• Male sex—OR, 2.49
• Longer duration of diabetes—OR, 1.06
• Albuminuria—OR, 3.24

Central subfield thickness

• Male sex—OR, 10.15
• Albuminuria—OR, 10.13

The findings differ in several ways from studies of African American, European, East Asian, and Latino populations.

A Contradiction

To investigate why both younger age and longer duration of diabetes were risk factors for DR, the researchers performed an exploratory analysis. Patients who had an onset of diabetes before age 40 had a mean HbA1c of 9.06% compared with 8.46% (P<0.001) for patients with later onset.

So, two opposing facts may be true: A group of patients may exist who have young onset of more severe diabetes and are at increased risk of advanced DR, but in general, a longer duration of diabetes is associated with increased DR risk.

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