Live probiotic supplementation mitigates caffeine-induced autonomic imbalance and nocturnal sympathetic predominance: implications for cardiovascular risk

Background Excessive caffeine intake is associated with sleep fragmentation and autonomic imbalance, particularly nocturnal sympathetic predominance, which may increase cardiovascular vulnerability. Emerging evidence suggests probiotics modulate gut–autonomic interactions; however, whether probiotic viability influences caffeine-related sleep and autonomic dysregulation remains unclear. Purpose To investigate whether live probiotic PS150 differentially improves sleep architecture and cardiac autonomic regulation compared with inactivated PS150 under conditions of caffeine-induced physiological stress. Methods Male rats exposed to high caffeine intake were randomized into three groups: caffeine control, caffeine plus live PS150, and caffeine plus inactivated PS150. Continuous 24-hour electroencephalography, electromyography, electrocardiography, and diaphragmatic electromyography recordings were performed. Sleep architecture and cardiac autonomic modulation were analyzed using heart rate variability (HRV) across vigilance states, including active wake (AW), quiet sleep (QS), and paradoxical sleep (PS). Results HRV analysis demonstrated that high caffeine exposure induced a shift toward sympathetic predominance during QS, as evidenced by increased low-frequency (LF) power and elevated LF/HF ratio. Supplementation with live probiotic PS150 significantly attenuated this sympathetic predominance, reflected by reductions in LF power and LF/HF ratio during QS, whereas inactivated PS150 exerted minimal effects. Notably, these autonomic improvements occurred without significant changes in overall heart rate or parasympathetic indices. In parallel, high caffeine exposure impaired sleep continuity, characterized by increased QS interruption frequency and reduced QS proportion. Live PS150 significantly reduced QS interruptions and increased QS duration compared with caffeine controls, while inactivated PS150 showed limited benefit. No significant intergroup differences were observed in paradoxical sleep. Conclusions Live probiotic PS150 selectively improves sleep continuity and reduces nocturnal sympathetic overactivity under caffeine-induced physiological stress. These findings highlight the importance of probiotic viability and suggest that modulation of gut–autonomic signaling may represent a promising non-pharmacological strategy to mitigate caffeine-related autonomic dysregulation and cardiovascular risk.