Glycated hemoglobin A1C level and the risk of diabetic retinopathy in Africa: A systematic review and meta-analysis

Diabetic retinopathy is a frequent cause of acquired blindness worldwide. Various studies have reported the effects of glycemic control on the risk of diabetic retinopathy, but the results remain inconclusive. Therefore, this meta-analysis was performed to determine the association between glycated hemoglobin A1C levels and diabetic retinopathy in Africa. A systematic search was performed using the PubMed, African Journals Online, Google Scholar, Scopus, and Wiley Online Library from inception to June 11, 2020, for observational studies addressing the association of hemoglobin A1c levels with diabetic retinopathy. The I2 statistic was used to check heterogeneity across the included studies. A random-effects model was applied to estimate the pooled effect size (OR) and respective 95% confidence interval across studies. A funnel plot and Egger's regression test were used to determine the presence of publication bias. Sensitivity analysis was used to determine the effect of a single study on the overall estimation. All statistical analyses were performed using STATA™ Version 14 software. A total of 23 articles with 18,099 study participants were included in this meta-analysis. In the present review, when HbA1c was analyzed as a categorical variable, poor glycemic control (HbA1c >7%) was associated with an increased risk of diabetic retinopathy when compared with good glycemic control (OR = 1.25; 95% CI; 1.14, 1.38). Similarly, when HbA1c was analyzed as a continuous variable, a higher HbA1c was associated with an increased risk of diabetic retinopathy (MD: 0.42, 95% CI; 0.11, 0.98). Our meta-analysis indicated evidence for poor glycemic control as an independent risk factor for the development of diabetic retinopathy in patients with diabetes mellitus. Therefore, the authors suggest that clinicians should advise their patients with diabetes to maintain their HbA1c levels within the normal range.