Greater 24-hour Blood Pressure Variability Is Associated With Higher Retinal Microvascular Resistance And Smaller Lumen Diameter In Healthy Normotensive Adults

Introduction: Elevated blood pressure (BP) is associated with damage to high flow, low resistance target organs such as the retina. Recent evidence suggests that 24-hour BP variability (BPV) is a novel risk factor for cardiovascular disease, independent of 24-hour average BP. However, whether 24-hour BPV is related to concentric retinal arteriole remodeling in healthy adults is unknown. Thus, the purpose of our study was to determine the degree to which 24-hour BPV is associated with retinal lumen diameter and vascular resistance in healthy young/middle-aged adults, independent of 24-hour average BP. Methods: Healthy, normotensive adults aged 25 to 60 years (n=40; 50% female) underwent measurements of retinal arteriole diameter and flow using laser speckle flowgraphy. 24-hour brachial BP was determined using ambulatory BP monitoring. BPV was calculated as the standard deviation of all BP recordings for systolic and diastolic BP. Retinal vascular resistance was calculated as ocular perfusion pressure divided by mean retinal flow across 4 arterioles. Aortic stiffness was measured as carotid-femoral pulse wave velocity (cfPWV). Results: Higher 24-hour systolic and diastolic average BP were associated with smaller retinal lumen diameter and elevated vascular resistance (P<0.05). Although both systolic BPV (r=0.391, P=0.012) and diastolic BPV (r=0.315, P=0.048) were associated with higher retinal vascular resistance, only diastolic BPV was associated with smaller retinal arteriole lumen diameter (r=-0.393, P=0.012). The association of greater diastolic BPV with smaller retinal arteriole lumen diameter (β=-0.363, P=0.01) and higher retinal vascular resistance (β=0.395, P=0.007) remained after adjusting for age, body mass index, cfPWV, and 24-hour average diastolic BP. Conclusion: Higher diastolic BPV may contribute to adverse remodeling of retinal arterioles in healthy normotensive adults independent of arterial stiffness and traditional cardiovascular disease risk factors. Future studies could utilize local metabolic vasodilation via diffuse luminance flicker to examine whether retinal arteriole autoregulatory mechanisms are impaired in individuals with higher BPV.