The "respiratory REM sleep without atonia benefit" on coexisting REM sleep behavior disorder - obstructive sleep apnea.

Rapid eye movement sleep behavior disorder (RBD) is a parasomnia characterized by dream-enactment behaviors that emerge during a loss of REM sleep atonia. In patients with RBD, obstructive sleep apneas syndrome (OSAS) frequently occurs as a comorbid entity. It has been reported that the presence of muscle tone during REM sleep (REM sleep without atonia-RSWA) could play a protective role in patients with OSAS RBD. In OSAS, recurrent episodes of complete or partial collapse of the upper airway occur during both, NREM and REM sleep. Particularly during sleep, the withdrawal of excitatory noradrenergic and serotoninergic inputs to the upper airway motor neurons deeply reduces the pharyngeal muscle activity, increasing the propensity for superior airway collapse. The present study compared for the first time the impact of OSAS in RBD patients with a subtype of OSAS patients with predominantly or isolated REM sleep-related OSAS (OSAS REM group) in the search of an adequate model to evaluate future therapeutic strategies. Our study found a significant lower nadir of oximetry values in OSAS RBD in comparison with the OSAS REM group. This reduction, that we called the "respiratory RSWA benefit", is in accordance with the decrease of the nadir oximetry values observed in patients with Parkinson disease and OSAS with or without RBD. We suggest that the group of OSAS REM patients is a natural model to evaluate the respiratory protective role of RSWA in patients with coexisting RBD-OSAS and Parkinson's disease.