Risk factors for diabetic retinopathy in people with Type 2 diabetes: A case–control study in a UK primary care setting

• Numerous DR near the diabetes diagnosis suggest frequent delay in this diagnosis.
• Patients with glaucoma or retinal arterial occlusion showed a reduced risk of DR.
• Patients with retinal vein occlusion showed an increased risk of DR.
• Desirable HDL levels showed a decreased risk of DR.

AimTo identify risk factors of diabetic retinopathy (DR) among people with Type 2 diabetes mellitus in UK primary care.MethodsA case–control study nested in a cohort of incident Type 2 diabetes identified in The Health Improvement Network database from 2000 to 2007. Cases were people with DR (N = 7735) and controls were a DR-free sample (N = 9395). No age restrictions were applied. Adjusted odds ratios and 95% CIs were estimated.Results21% of DR cases were identified during the first semester after Type 2 diabetes diagnosis. After controlling for delay on the Type 2 diabetes diagnosis, the DR risk increased with the duration of diabetes. DR increased with a mean systolic BP ≥150 mmHg (1.18; 1.10–1.27), high alcohol consumption (1.34; 1.11–1.61), glycated haemoglobin (≥75 to <86: 1.14; 1.00–1.31; ≥86 to <97 mmol/mol: 1.25; 1.07–1.45; ≥97 mmol/mol: 1.21; 1.07–1.37), microalbuminuria (1.16; 1.06–1.27), and retinal vein occlusion (2.47; 1.67–3.66). Glaucoma and retinal arterial occlusion showed an OR of 0.71 (0.60–0.84) and 0.63 (0.40–1.01), respectively. HDL ≥1.55 mmol/l (0.88; 0.80–0.98), high triglycerides (2.3–5.6 mmol/l: 0.90; 0.82–0.99; >5.6 mmol/l: 0.85; 0.64–1.13) or smoking (0.89; 0.81–0.97) had a slightly reduced DR risk. Users of hypoglycaemic agents had an increased DR risk.ConclusionSome DR cases were identified near the diabetes diagnosis date suggesting that a delayed diabetes diagnosis is still common. Glaucoma, retinal arterial occlusion and high HDL levels were inversely associated with DR, while retinal vein occlusion, alcohol and other well-known risk factors were positively associated.