Retinal Vascular Changes and Their Correlation with Cardiovascular Risk Markers in an Adult Nigerian Cohort: A 5-Year Longitudinal Study

The retinal vasculature offers a non-invasive window into systemic microvascular health, and quantitative retinal vascular analysis has been proposed as a biomarker of cardiovascular risk. Longitudinal evidence linking retinal vascular changes to cardiovascular outcomes in African populations is absent from the literature. This study examines retinal vascular changes and their correlation with cardiovascular risk markers in an adult Nigerian cohort followed over five years. A prospective longitudinal cohort study will recruit 800 adults aged 35 to 65 years with no prior history of cardiovascular disease from community health enumeration areas in Ibadan, Oyo State. At baseline and annual follow-up visits, retinal fundus photography will be performed and retinal arteriolar-to-venular ratio (AVR), retinal arteriolar calibre, venular calibre, and retinal fractal dimension will be quantified using validated semi-automated software. Cardiovascular risk markers including blood pressure, fasting lipids, blood glucose, body mass index, carotid intima-media thickness, and electrocardiographic findings will be simultaneously recorded. Mixed-effects longitudinal models will examine temporal associations between retinal vascular parameters and cardiovascular risk trajectories. Retinal vascular analysis as a cardiovascular biomarker is well-validated in European and Asian longitudinal cohorts but entirely unstudied in sub-Saharan African populations where hypertension and stroke burden are highest globally. This study generates a foundational longitudinal dataset for Nigeria and contributes to understanding whether retinal imaging can serve as an affordable, non-invasive cardiovascular risk stratification tool in Nigerian primary care. Recommendations will address translation of retinal imaging findings into clinical cardiovascular risk prediction tools adapted for Nigerian settings. Keywords: retinal vasculature, cardiovascular biomarker, arteriolar-venular ratio, longitudinal cohort, Nigeria