The Parkinson's Disease Sleep Scale–2 (PDSS-2): Validation of the Spanish Version and Its Relationship With a Roommate-Based Version

Background: Because of the prevalence and impact of sleep disorders in Parkinson's disease (PD), valid instruments for their evaluation and monitoring are necessary. However, some nocturnal sleep disorders may go unnoticed by patients themselves. Objectives: To validate a pan-Spanish version of the Parkinson's Disease Sleep Scale Version 2 (PDSS-2) and to test the relationships between the PDSS-2 and a PDSS-2 roommate version. Methods: PD patients (n = 399) from seven Spanish-speaking countries were included. In addition to the tested PDSS-2 scales, valid measures for sleep disorders and both motor and nonmotor manifestations were applied. Acceptability, dimensionality, reliability, precision, and construct validity were explored, as well as discrepancies and agreement between the PDSS-2 and the roommate version. Results: PDSS-2 showed negligible floor and ceiling effects. Four factors (57% of the variance) were identified. Reliability parameters were satisfactory: alpha = 0.84; item homogeneity coefficient = 0.27; corrected item total correlation = 0.28 to 0.61; and test-retest reliability (average kappa = 0.70; intraclass correlation coefficient [ICC] = 0.83). The standard error of measurement was 5.84, and correlations with other scales assessing nocturnal sleep were high (r_S = 0.62–0.56). In comparison to the patient-based total score, the by proxy total score showed no significant difference, high correlation (r_S = 0.70), and acceptable agreement (ICC = 0.69), but there were discrepancies in two or more points in 18% of item scores. Conclusions: The Spanish version of the PDSS-2 has shown satisfactory clinimetric attributes. Acceptability and precision data are presented for the first time. The PDSS-2 roommate version could be useful to complement the patient-based evaluation, but additional studies are needed.