Obstructive sleep apnea may reduce a diagnostic accuracy of video-polysomnography for idiopathic REM sleep behavior disorder.

Background: Severe obstructive sleep apnea (OSA) in patients with rapid eye movement (REM) sleep behavior disorder (RBD) may result in frequent fragmentation of REM sleep and consequently lead to a false negative diagnosis of RBD on a video-polysomnography (video-PSG). Thus, we determined whether OSA has the negative impact on video-PSG diagnostic accuracy for RBD.

Methods: Patients with clinically diagnosed idiopathic RBD were included. RBD was confirmed if a video-PSG demonstrated complex motor behavior during REM sleep or REM sleep without atonia (RWA). Motor behavior was measured using the RBD Severity Scale. Cohen's kappa coefficient was calculated for qualitative assessment of RWA. A stepwise logistic regression analysis was performed.

Results: Of a total 254 patients included, a diagnosis of RBD was confirmed by a video-PSG in 221 patients (87.0%). RWA, vocalization, and axial or proximal muscle movements in REM sleep were noted in 86.6%, 58.3%, and 35.9%, respectively. A video-PSG diagnosis of RBD was less likely associated with severe OSA (odds ratio [OR] 0.284, p = 0.010) and moderate OSA (OR 0.404, p = 0.071) whereas was more likely associated with longer REM sleep time (OR 1.036, p < 0.001). In 43 patients who underwent a continuous positive airway pressure (CPAP) titration study, a diagnosis of RBD was more common on a CPAP titration study (88.4%) than on a first video-PSG (65.1%) (p = 0.013). Twelve (27.9%) of 43 CPAP patients were diagnosed with RBD according only to CPAP titration study.

Conclusions: OSA that requires CPAP may reduce a diagnostic accuracy for RBD by a video-PSG. False negative results were probably due to frequent electromyographic artifacts and/or severe sleep disruption from apneic events during REM sleep.