Parkinson's Disease Sleep Scale: validation study of a Spanish version

The Parkinson's Disease Sleep Scale (PDSS) is the first published bedside clinical tool to specifically measure sleep disturbances in Parkinson's disease (PD). The objective of the present study was to carry out a metric analysis of a Spanish version (PDSS-SV) using a cross-sectional study of 100 PD patients who participated in the study. Usual measures for PD and mental status were applied by neurologists. Patients completed the Epworth Sleepiness Scale, Parkinson's Disease Questionnaire-39 Items (PDQ-39), and PDSS-SV. PDSS internal consistency (Cronbach's alpha, 0.77; significant item-total correlation for 11 items) was satisfactory. PDSS showed high test-retest reliability (intraclass correlation coefficient for items, 0.79-0.99; for total score, 0.94). Standard error of measurement was 9.80 (crossover) and 5.01 (longitudinal). Scores were distributed uniformly, with low floor and ceiling effect (1%). PDSS scores were correlated significantly with depression (Hamilton Depression Rating Scale, r(S) = -0.55; P < 0.0001) and quality of life (PDQ-39 Summary Index, r(S) = -0.26; P = 0.007), but not with clinical variables. Self-perception of mood disorder, pain, or hallucinations correlated individually with PDSS scores, and a factor explaining 65% of the variance was found. The assessment of PD sleep disorders with the PDSS met some basic standards required for health status measures.