Cyclic alternating pattern analysis in REM sleep behavior disorder.

Objective: Rapid eye movement (REM) sleep behavior disorder (RBD) is a type of REM parasomnia characterized by complex motor activity during REM sleep. In this study, cyclic alternating pattern (CAP) in patients with idiopathic RBD was analyzed to evaluate the expression of arousal instability of NREM sleep.

Methods: A total of 31 idiopathic RBD patients and age- and gender-matched 21 control subjects were consecutively recruited. Conventional sleep polysomnographic recording parameters and CAP parameters were compared between RBD and the control group.

Results: The number of CAP cycles (120.13 ± 113.56, p = 0.007), CAP sequences (20.9 ± 18.15, p < 0.001), CAP index (25.14 ± 24.44, p = 0.017), and CAP rate (24.07 ± 13.22, p = 0.016) were all significantly higher in RBD patients compared to the control group. The increase in CAP sequences was observed in phase A2 and A3 subtypes while phase A1 subtype was significantly lower in RBD patients. A significant positive correlation was observed between disease duration with total CAP time (r = 0.289, p = 0.042) and A3 index (r = 0.32, p = 0.024). There was a negative correlation between the age and A1 index (r = -0.4491, p = 0.0001).

Conclusion: To our knowledge this is the first polysomnographic clinical study which evaluated CAP parameters in RBD. Increased CAP rate found may be considered as a sign showing that NREM sleep may also be affected in RBD patients. Therefore, CAP analysis may be important to enlighten the pathogenesis of parasomnias.