Effect Of Prolonged Sitting On Dynamic Cerebral Autoregulation

In contemporary society, prolonged sitting has become a widespread lifestyle habit, posing a risk factor for cerebral disease. However, the precise physiological mechanism through which prolonged sitting increases the risk of cerebral disease, especially in the posterior circulation, remains unclear. We hypothesize that prolonged sitting induces cerebrovascular dysfunction in both the anterior and posterior circulations. PURPOSE: To test this hypothesis, we examined the impact of a 4-hour continuous sitting period on dynamic cerebral autoregulation (dCA) in both the anterior and posterior circulations, fundamental in regulating cerebral blood flow in healthy young adults. METHODS: Thirteen young healthy participants remained seated for 4 hours without moving their lower limbs. Measurements of mean arterial pressure (MAP), and mean blood velocities of the middle and posterior cerebral arteries (MCA Vm and PCA Vm, respectively) were evaluated before and after a 4-hour continuous sitting period. To assess the dCA in both the anterior and posterior circulations, transfer function analysis (TFA) was employed using MAP and cerebral blood velocity in both the anterior and posterior circulations (i.e., MCA Vm and PCA Vm). RESULTS: After 4 hours of continuous sitting, a notable decrease in MCA Vm (69 ± 11 cm/s vs. 62 ± 11 cm/s, P = 0.011) was observed, whereas MAP and PCA Vm showed no significant change compared to baseline (MAP; 88 ± 8 mmHg vs. 90 ± 10 mmHg, P = 0.376 and PCA Vm; 45 ± 8 cm/s vs. 45 ± 7 cm/s, P = 0.914). In addition, the evaluation of dCA in both the anterior and posterior circulation using TFA low-frequency phase and normalized gain (ngain) indicated no significant changes following the 4-hour sitting period (anterior circulation: phase; 1.25 ± 0.24 radian vs. 1.25 ± 0.25 radian, P = 0.652 and ngain; 1.99 ± 1.09 db vs. 1.88 ± 0.88 db, P = 0.290, posterior circulation: phase; 1.13 ± 0.35 radian vs. 1.21 ± 0.23 radian, P = 0.481 and ngain; 2.02 ± 0.94 db vs. 1.93 ± 0.91 db, P = 0.751). CONCLUSION: Despite the decrease in anterior cerebral blood velocity due to prolonged sitting, it is remarkable that the dCA in both the anterior and posterior circulations remains consistent throughout the 4-hour sitting period. JST SPRING [grant number JPMJSP2159].