Changes in cardiac variability after REM sleep deprivation in recurrent nightmares

Abstract

Study objectives: To assess whether dysfunctional autonomic regulation during REM sleep as indexed by heart rate variability (HRV) is a pathophysiological factor in frequent nightmares (NMs).

Design: Monitoring with polysomnography (PSG) and electrocardiography (ECG) for 3 consecutive nights: Night 1 (N1), adaptation night; N2, administration of partial REM sleep deprivation; N3, recovery night. Differences between NM and control (CTL) groups assessed for ECG measures drawn from wakefulness, REM sleep, and Stage 2 sleep on both N1 and N3.

Setting: Hospital-based sleep laboratory.

Participants: Sixteen subjects with frequent NMs (> or = 1 NM/week; mean age = 26.1 +/- 8.7 years) but no other medical or psychiatric disorders and 11 healthy comparison subjects ( < 1 NM/month; mean age = 27.1+/- 5.6 years).

Results: NM and CTL groups differed on 2 REM sleep measures only on N1; the NM group had longer REM latencies and REM/NREM cycle durations than did the CTL group. No differences were found on time domain and absolute frequency domain ECG measures for either N1 or N3. However, altered HRV for the NM group was suggested by significantly higher LFnu, lower HFnu, and higher LF/HF ratio than for the CTL group.

Conclusions: Results are consistent with a higher than normal sympathetic drive among NM subjects which is unmasked by high REM sleep propensity. Results also support a growing literature linking anxiety disorders of several types (panic disorder, posttraumatic stress disorder (PTSD), generalized anxiety disorder) to altered HR variability.

Figure 1

Normalized low frequency (LFnu) and high frequency (HFnu) power in REM sleep, Stage 2 sleep, and Awake for Nights 1 and 3. From Night 1 to Night 3, REM LFnu decreases and REM HFnu increases for the CTL but not the NM group. The pattern reflects a continuing relative sympathetic activation and parasympathetic withdrawal following REM deprivation for the NM group. Plots are for 2 × 2, Groups (NM, CTL) × Nights (N1, N3), MANOVA interaction effects (see text). Group simple effects: ***P < 0.0005; **P < 0.01; *P < 0.05.

Figure 2

Pearson correlations between average home log dream anxiety ratings (1 to 9 scale) and normalized REM sleep, Stage 2 sleep and Awake state cardiac variability measures for laboratory Night 1 (N1, left panel) and Night 3 (N3, right panel). *P < 0.05; †P = 0.088.