Validation of the Japanese version of the REM sleep behavior disorder questionnaire (RBDQ-JP)

Abstract Background The rapid eye movement (REM) sleep behavior disorder (RBD) questionnaire (RBDQ)- Hong Kong was the first tool developed for quantifying the severity of RBD. This study was conducted to validate the Japanese version of the questionnaire and to investigate its reliability, validity, and responsiveness. Methods Patients with idiopathic RBD and sex and age-matched healthy controls completed the Japanese version of the questionnaire (RBDQ-JP). In addition to the evaluation of its reliability and validity, the questionnaire scores were compared between those earned before and those earned after pharmaceutical treatment to assess the questionnaire’s responsiveness. Results The questionnaire demonstrated high test–retest reliability and moderate internal consistency. The best cut-off score was 19/20 with a sensitivity of 97.2% and a specificity of 97.5%. Exploratory factor analysis revealed that the questionnaire consists of the following two factors: Factor 1 , Dream and dream-related behaviors and Factor 2 , Violent/complex behaviors. Among the patients, significant correlation was found between the rate of change of questionnaire score and the clinical global impression improvement score with pharmaceutical treatment ( rs = −0.829, p < 0.01). Conclusions The RBDQ-JP provides satisfactory reliability, validity, and responsiveness. The questionnaire is suitable for severity assessment and for assessing the RBD treatment outcome.