Cardiac autonomic regulation during sleep in idiopathic REM sleep behavior disorder

Objective: To assess cardiac autonomic and respiratory changes from stage 2 non-rapid eye movement sleep (NREM) to rapid eye movement (REM) sleep in subjects with idiopathic REM sleep behavior disorder (RBD) and controls. We tested the hypothesis that REM-related cardiorespiratory activation is altered in subjects with RBD. Design: Retrospective case-control study. Setting: University hospital-based sleep research laboratory. Patients: Ten subjects with idiopathic RBD (2 women, mean age 63.4 +/- 6.2 years) and 10 sex- and age-matched controls (mean age 63.9 +/- 6.3 years). Intervention: One-night polysomnography was used to assess R-R variability during NREM and REM sleep. Measurements and Results: Spectral analysis of R-R interval and respiration were performed. Mean R-R interval, low-frequency (LF) and high-frequency (HF) components in both absolute and normalized units (LFnu and HFnu), and the LF/HF ratio were obtained from 5-minute electrocardiogram segments selected during NREM and REM sleep under stable conditions (stable breathing pattern, no microarousals or leg movements). Respiratory frequency was also assessed. Values obtained were then averaged for each stage and analyzed by 2 x 2 analysis of variance with group (RBD subjects and controls) as factor and state (NREM and REM) as repeated measures. RR interval, HF, and HFnu components decreased from NREM to REM in controls but did not change in RBD subjects (Interaction P < 0.05). LFnu (interaction P < 0.001), LF/HF (interaction P < 0.001), and respiratory frequency (interaction P < 0.05) increased from NREM to REM sleep in controls but remained stable in RBD subjects. Conclusion: REM-related cardiac and respiratory responses are absent in subjects with idiopathic RBD.