Effect of Acute Sleep Deprivation on Cardiac Autonomic Stress Reactivity in Healthy Young Adults

Background: Sleep deprivation is increasingly recognized as a significant contributor to autonomic imbalance and cardiovascular risk, being associated with reduced parasympathetic activity and heightened sympathetic drive; therefore, this study aims to evaluate the effect of acute sleep deprivation on cardiac autonomic stress reactivity in healthy young adults.Methods: This cross-sectional study included 30 healthy male participants.Cardiac autonomic function tests were performed under two conditions: after normal sleep and following acute sleep deprivation.Parasympathetic reactivity was assessed using the deep breathing test, Valsalva manoeuvre, and active standing test, while sympathetic reactivity was evaluated using the isometric handgrip test and orthostatic blood pressure response.Data were expressed as mean±SD or median (range).Results: Acute sleep deprivation resulted in a significant reduction in parasympathetic activity, evidenced by decreased ΔHR during deep breathing (p=0.0001) and reduced Valsalva ratio (p=0.02).Tachycardia latency decreased (p=0.007),whereas bradycardia latency increased (p=0.03).Sympathetic reactivity showed a significant increase, with elevated ΔDBP during the handgrip test at 1 and 2 minutes (p<0.05).Orthostatic systolic blood pressure changes were not statistically significant.Conclusion: Acute sleep deprivation leads to a significant shift toward sympathetic dominance with concomitant reduction in parasympathetic tone, indicating an autonomic imbalance that may predispose to cardiovascular morbidity.