Retinal venular vessel diameters are smaller during ten days of bed rest

Abstract

Introduction: Older individuals experience cardiovascular dysfunction during extended bedridden hospital or care home stays. Bed rest is also used as a model to simulate accelerated vascular deconditioning occurring during spacefight. This study investigates changes in retinal microcirculation during a tenday bed rest protocol. Ten healthy young males (22.9± 4.7 years; body mass index: 23.6± 2.5 kg·m–2) participated in a strictly controlled repeated-measures bed rest study lasting ten days. High-resolution images were obtained using a hand-held fundus camera at baseline, daily during the 10 days of bed rest, and 1 day after re-ambulation. Retinal vessel analysis was performed using a semi-automated software system to obtain metrics for retinal arteriolar and venular diameters, central retinal artery equivalent and central retinal vein equivalent, respectively. Data analysis employed a mixed linear model. At the end of the bed rest period, a signifcant decrease in retinal venular diameter was observed, indicated by a signifcantly lower central retinal vein equivalent (from 226.1 µm, CI 8.90, to 211.4 µm, CI 8.28, p= .026), while no signifcant changes in central retinal artery equivalent were noted. Prolonged bed rest confnement resulted in a signifcant (up to 6.5%) reduction in retinal venular diameter. These fndings suggest that the changes in retinal venular diameter during bedrest may be attributed to plasma volume losses and refect overall (cardio)-vascular deconditioning.