Is REM sleep behavior disorder a friend or foe of obstructive sleep apnea? Clinical and etiological implications for neurodegeneration

Rapid eye movement sleep behavior disorder (RBD) is a parasomnia characterized by loss of muscle atonia during rapid eye movement sleep, associated with complex motor enactment of dreams. Obstructive sleep apnea (OSA) is a relatively common sleep disorder characterized by repetitive episodes of upper airway obstruction while sleeping, which can result in hypoxemia and sleep fragmentation. Even though the nature of RBD and OSA is different, OSA may sometimes be accompanied by RBD symptoms. Accordingly, it is reasonable to distinguish these 2 sleep disorders in people with dream enactment behaviors. Although RBD and OSA share similar sleep phenomena, their association has yet to be elucidated. Herein we draw attention to various RBD-mimicking conditions, RBD combined with OSA, and the relationship between RBD and OSA. Furthermore, the clinical implications of OSA in neurodegeneration and the optimized management of RBD combined with OSA are also discussed in this review.