Cross-cultural adaptation and measurement properties of the Brazilian Portuguese version of the Parkinson’s disease sleep scale-2 (PDSS-2)

Objectives

The Parkinson’s Disease Sleep Scale-2 (PDSS-2) is an updated tool designed to identify specific sleep disturbances in individuals with Parkinson’s disease (PD). However, for its application in Brazil, a process of cross-cultural adaptation and validation of its measurement properties is required.

Methods

This methodological study adapted the PDSS-2 to Brazilian Portuguese (PDSS-2-Br) and assessed its measurement properties, including internal consistency, test-retest reliability, measurement error, construct validity, and interpretability. The adapted scale was administered on two occasions within a 7-day interval to 50 individuals with PD. Test–retest reliability was evaluated using kappa statistics (k) for individual items, the intraclass correlation coefficient (ICC) for total scores, the standard error of measurement (SEM), the minimal detectable change (MDC), and a Bland-Altman plot. Construct validity was assessed through Spearman correlation coefficients between the PDSS-2-Br and independent variables, while interpretability was evaluated by examining ceiling and floor effects.

Results

The PDSS-2-Br showed satisfactory semantic, idiomatic, cultural, and conceptual equivalence. It also demonstrated good internal consistency (α=0.64), adequate test-retest reliability between items (κw 0.42–0.94, 95 % CI=0.30–0.95) and total score (ICC=0.94; 95 % CI=0.89–0.96), acceptable measurement error (SEM, 2.07 points; MDC, 5.74 points), with no ceiling and floor effects, and 87.5 % of pre-defined hypotheses were confirmed, indicating adequate construct validity (Spearman correlations coefficients for the r_s=0.50, p<0.001) of the PDSS-2-Br.

Conclusion

The measurement properties of the PDSS-2-Br are consistent with those of the original version, confirming the scale's validity and reliability in assessing sleep disorders among the Brazilian population with PD.