Changes in cardiac variability after REM sleep deprivation in recurrent nightmares

Area of Science:

• Sleep Medicine
• Autonomic Neuroscience
• Cardiology

Background:

• Frequent nightmares (NMs) are associated with various psychological conditions.
• Autonomic nervous system (ANS) regulation during sleep, particularly REM sleep, is crucial for physiological stability.
• Heart rate variability (HRV) is a non-invasive measure of ANS function.

Purpose of the Study:

• To investigate if dysfunctional autonomic regulation during REM sleep, assessed by HRV, is a pathophysiological factor in frequent nightmares.
• To compare HRV parameters between individuals with frequent nightmares and healthy controls.

Main Methods:

• Polysomnography (PSG) and electrocardiography (ECG) monitored 16 frequent nightmare subjects and 11 healthy controls over 3 nights.
• REM sleep deprivation and recovery nights were included to assess ANS responses.
• ECG measures were analyzed during wakefulness, REM sleep, and Stage 2 sleep.

Main Results:

• Nightmare (NM) and control (CTL) groups showed differences in REM latency and cycle duration on the adaptation night.
• No significant differences in time or frequency domain HRV measures were found on adaptation or recovery nights.
• However, the NM group exhibited altered HRV, with higher LFnu, lower HFnu, and a higher LF/HF ratio during REM sleep, suggesting increased sympathetic drive.

Conclusions:

• Findings suggest heightened sympathetic nervous system activity in individuals with frequent nightmares, particularly during REM sleep.
• Altered HRV in nightmare sufferers supports a link between autonomic dysfunction and NMs.
• These results align with existing literature connecting anxiety disorders (e.g., PTSD) with abnormal HRV patterns.