Incidence and risk factors of severe non‐proliferative/proliferative diabetic retinopathy: More than a decade follow up in the Tehran Lipids and Glucose Study

AIMS/INTRODUCTION: To examine the incidence rate of severe non-proliferative and proliferative diabetic retinopathy (severe-NPDR/PDR) and determine its potential risk factors. MATERIALS AND METHODS: The study consisted of 1,169 participants (675 women) with type 2 diabetes mellitus, aged ≥20 years. A trained interviewer collected information about the history of pan-retinal photocoagulation as a result of diabetic retinopathy. Multivariable Cox proportional hazards regression models were applied. RESULTS: We found 187 cases (126 women) of severe-NPDR/PDR during a median follow-up period of 12.7 years; the corresponding incidence rate was 13.6 per 1,000 person-years. Being overweight (hazard ratio [HR], 95% confidence interval [CI] 0.60, 0.39-0.92) and obese (HR 0.48, 95% CI 0.27-0.83) were associated with lower risk, whereas being smoker (HR 1.75, 95% CI 1.12-2.74), having fasting plasma glucose levels 7.22-10.0 mmol/L (HR 2.81, 95% CI 1.70-4.62), fasting plasma glucose ≥10 mmol/L (HR 5.87, 95% CI 3.67-9.41), taking glucose-lowering medications (HR 2.58, 95% CI 1.87-3.56), prehypertension status (HR 1.65, 95% CI 1.05-2.58) and newly diagnosed hypertension (HR 1.96, 95% CI 1.06-3.65) increased the risk of severe-NPDR/PDR. Among newly diagnosed diabetes patients, being male was associated with a 59% lower risk of severe-NPDR/PDR (HR 0.41, 95% CI 0.21-0.79). Furthermore, patients who had an intermediate level of education (6-12 years) had a higher risk of developing PDR (HR 1.86, 95% CI 1.05-3.30) compared with those who had <6 years of education. CONCLUSIONS: Among Iranians with type 2 diabetes mellitus, 1.36% developed severe-NPDR/PDR annually. Normal bodyweight, being a smoker, out of target fasting plasma glucose level, prehypertension and newly diagnosed hypertension status were independent risk factors of severe-NPDR/PDR. Regarding the sight-threatening entity of advanced diabetic retinopathy, the multicomponent strategy to control diabetes, abstinence of smoking and tight control of blood pressure should be considered.