Association of insulin treatment versus oral hypoglycaemic agents with diabetic retinopathy and its severity in type 2 diabetes patients in Cameroon, sub-Saharan Africa

Background: Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease associated with multiple macro and microvascular complications, diabetic retinopathy (DR) being the commonest one. Recent literature has reported an increased risk of DR with insulin use. Methods: We carried out a cross-sectional study at the Ophthalmology Department of the Douala General Hospital (DGH) during a 2-year period to explore the association between insulin treatment and both DR and its severity as compared with oral hypoglycemic agents (OHAs) in Cameroonian T2DM patients aged >= 35 years, and who were all screened for DR through eye examination including exhaustive retinal evaluation. Results: In total, medical files of 134 T2DM patients were analyzed. The frequency of DR was 54.1% among patients on OHA and 73.9% among those on insulin treatment, giving an overall frequency of 57.5%. There were significantly more OHA treated patients than insulin treated patients (82.8% vs. 17.2%, P< 0.001). As expected, both the OHA and insulin groups were comparable by age, sex, duration of diabetes, past history of hypertension, alcohol misuse, and current tobacco smoking. DR was almost significantly more frequent in T2DM patients under insulin regimen than in patients under OHA [73.9% vs. 54.1%; odds ratio (OR) 2.4; 95% confidence interval (CI), 0.9-6.6; P= 0.06]. Proliferative diabetic retinopathy (PDR) was significantly more observed in insulin treated patients than in OHA treated patients (34.8% vs. 15.3%; OR 2.95; 95% CI, 1.1-8; P= 0.035). Irrespective of staging, the frequency of diabetic macular edema (DME) was significantly higher in the insulin group than in the OHA group (43.5% vs. 19.8%; OR 3.1; 95% CI, 1.2-8; P= 0.019). Conclusions: Compared with OHA, insulin therapy may be associated with DR, DR severity and DME in these T2DM sub-Saharan African patients.