The utility of a Korean version of the REM sleep behavior disorder screening questionnaire in patients with obstructive sleep apnea

Purpose To explore the utility of a Korean version of the rapid eye movement sleep behavior disorder screening questionnaire (RBDSQ-K) to discriminate patients with idiopathic REM sleep behavior disorder (iRBD) from patients with obstructive sleep apnea (OSA) and healthy subjects. Methods Participants with iRBD (n = 47) and OSA (n = 213) were diagnosed by polysomnography. In healthy subjects (n = 58), RBD was excluded by medical history without polysomnography. Receiver operating characteristic curve analysis was used to identify the optimal cutoff value of the RBDSQ-K for iRBD. Results RBDSQ-K score was higher in iRBD subjects than in OSA subjects and healthy subjects (both p < 0.001). The optimal cutoff was 6.5 to distinguish iRBD subjects from OSA subjects and 4.5 to distinguish iRBD subjects from healthy subjects. The corresponding sensitivity and specificity was high for detecting iRBD from OSA and healthy subjects. The percentages of individuals with RBDSQ-K scores ≥ 5 and ≥ 7 were higher in OSA subjects with daytime sleepiness (36.1% and 13.8%, respectively) than in OSA subjects without daytime sleepiness (12.0% and 3.1%, respectively). Apnea-hypopnea index had no influence on RBDSQ-K score. Cronbach's alpha for the RBDSQ-K was 0.768, indicating a high degree of internal consistency. Conclusions The RBDSQ-K had acceptable sensitivity and specificity for screening persons with probable RBD from healthy subjects and OSA subjects when the cutoff score was 4.5 and 6.5 points, respectively. However, attention must be paid to the possibility of false positives when using this scale, especially in OSA subjects with daytime sleepiness.