Effect of Prolonged Sitting on Cerebral Endothelial Function

Prolonged sitting increases the risk of cerebrovascular disease independent of physical inactivity. Since prolonged sitting has been reported to gradually decrease cerebral blood flow (CBF), we hypothesized that prolonged sitting causes cerebrovascular dysfunction. PURPOSE: To test this hypothesis, we examined whether cerebral endothelial function, one of the important functions of CBF regulation, is attenuated after prolonged recumbent sitting in healthy young adults. METHODS: 5 young healthy participants were asked to sit for 4 hours without moving their lower limbs. During sitting, the blood flow and shear rate (SR) in the internal carotid artery (ICA) were hourly assessed using duplex Doppler ultrasound. The cerebral endothelial function was evaluated by the flow-mediated dilation in the ICA (cFMD) via 30 s carbon dioxide (CO2) inhalation technique (end-tidal partial pressure of CO2: +9 mmHg) before and after 4 hours sitting. RESULTS: During 4 hours of sitting, ICA blood flow gradually decreased (P = 0.002), however, ICA SR was unchanged (P = 0.212). In addition, cFMD was maintained during 4 hours of sitting (P = 0.538). CONCLUSIONS: These results suggest that cerebral endothelial function may not be blunted by prolonged sitting, despite decreased CBF.