SCOPA-sleep and PDSS: two scales for assessment of sleep disorder in Parkinson's disease.

This study evaluated the comparative validity and usefulness of the Parkinson's Disease Sleep Scale (PDSS) and the Scales for Outcomes in PD-Sleep Scale (SCOPA-S), two disease-specific rating scales for assessing sleep disorders in Parkinson's disease (PD). Hoehn and Yahr staging (HY), SCOPA-Motor, Mini-Mental State Examination, Clinical Impression of Severity Index for PD, Hospital Anxiety and Depression Scale, EuroQoL, and SCOPA-Psychosocial, in addition to PDSS and SCOPA-S (night-time sleep (NS) and daytime sleepiness (DS) subscales), were applied to 187 consecutive PD patients. PDSS and SCOPA-S proved similar in acceptability, scaling assumptions, precision, and internal consistency (Cronbach's alpha = 0.82-0.84). Factor analysis revealed five separate factors for PDSS (67% of the variance) and one factor for each SCOPA-S subscale (60% of the variance for NS and 57% for DS). Correlation coefficient between PDSS and SCOPA-S NS was -0.60. Sleep scales correlated moderately with mood, low-to-moderate with HRQoL, and low with the rest of measures. PDSS and SCOPA-S DS discriminated between patients grouped by HY severity levels and disease duration. Cutoff points of 82/83 for PDSS and 6/7 for SCOPA-S NS were drawn to identify PD patients with sleep problems. Depression/anxiety scores explained 26% for PDSS and 22% for SCOPA-S NS scores. Both scales provide valid, reliable, and useful means to evaluate sleep disorders in PD. PDSS may be used to obtain a profile about potential causes of "bad sleep," but is barely useful to assess DS, whereas SCOPA-S assesses nocturnal sleep disorders and daytime somnolence at a similar extent, without exploring the potential causes.