The associations of arterial stiffness with functional visual decline in U.S. adults – The NHANES 2005–2008 8 survey cycle

Background Arterial stiffness causally predicts metabolic syndrome, hypertension, obesity, insulin resistance, type 2 diabetes and cardiovascular morbidity and mortality among adolescents and adults. However, whether arterial stiffness predicts adverse visual health remains unclear. Retinal microvascularisation is linked to systemic circulation. Loss of vessel wall elasticity may result in excessive pressure fluctuations that enable retinal capillary malperfusion, ischaemia, and dysfunctional visual field defects. Purpose We examined the independent association of estimated pulse wave velocity (ePWV) with functional visual field sensitivity. Methods Altogether 4,853 adults (aged ≥ 40 years with gradable visual field image data) from the National Health and Nutrition Examination Survey 2005–2008 cycles were included. We calculated ePWV using age and arterial pressure stratified by cardiovascular risk as previously validated. Visual field damage was quantified as the total count of depressed points via Frequency Doubling Technology (FDT) perimetry. We estimated incidence rate ratios (IRRs) using multivariable Poisson regression, accounting for complex survey design and weights. The models were adjusted for sex, adiposity estimated with waist circumference to height ratio, smoking status, diabetes, and heart disease. Mediation analysis was performed to determine if diabetes mediates the pathway between arterial stiffness and total defect count. Age was omitted due to high correlation (r=0.89). We performed a sensitivity analysis by trimming the extreme upper 1% of visual field defects (n= 60), minimising the influence of non-vascular outliers. Results In the fully adjusted model, ePWV was significantly associated with visual field defects (IRR: 1.08; 95% CI: 1.06–1.11; p<0.001). Sensitivity analysis excluding individuals with pre-existing cardiovascular disease was consistent, such that ePWV was associated with visual field defect (IRR: 1.08; 95% CI: 1.05–1.12; p<0.001). Predictive marginal analysis across ePWV quartiles revealed a significant linear dose-response relationship. The number of predicted visual field defects rose from 3.06 in the most elastic (Q1) to 4.29 in the stiffest quartile (Q4), representing a 40.2% increase (p<0.001). Participants at Q4 had a worse association between ePWV and visual field defect (IRR: 1.40; 95% CI: 1.18–1.67; p<0.001). Type 2 diabetes partly mediated the association of arterial stiffness and field defect count (β=0.104, 95% CI: 0.047–0.162; p<0.001), accounting for 15.8% of the total effect of ePWV on total defect count. Conclusion Arterial stiffness was associated with functional visual field loss, partly mediated by type 2 diabetes. The observed dose-response relationship suggests that the retinal microvasculature may be susceptible to central artery stiffening-induced pulsatile haemodynamic stress.