Parkinson's disease sleep scale--validation of the revised version PDSS-2.

BACKGROUND: The previous Parkinson's disease sleep scale (PDSS) is a 15-item visual analogue scale that assesses the profile of nocturnal disturbances in Parkinson's disease (PD) patients.
OBJECTIVE: To extend the scale so that it becomes a frequency measure scale with five categories and encompasses unmet needs such as restless legs syndrome, akinesia, pain, and sleep apnea.
METHODS: For validation of the PDSS-2, PD patients' ratings and investigators' interviews were compared to ratings from a semistructured interview with a caregiver/partner, and to related scales. PDSS-2 was repeated for test-retest-reliability after 1-3 days.
RESULTS: A total of 113 PD patients showed a mean (SD) total score of 16.5 (±8.9) (range: 2-40) indicating mild to moderate sleep disturbances. PDSS-2 item-total correlation for proving internal consistency was satisfactory (correlations >0.30). From a factor analysis, three subscales were derived: (1) "motor problems at night," (2) "PD symptoms at night" and (3) "disturbed sleep." The alpha coefficient for the total score was 0.73, for subscales 0.47 to 0.66. The test-retest-reliability intra-class-coefficient for the total score was 0.80, with 0.69 and 0.77 within the subscales. For discriminative validity, significant differences were found in the PDSS-2 total score depending on CGI and Hoehn and Yahr severity levels. A comparison between caregivers' and patients' ratings was carried out.
CONCLUSION: The PDSS-2, with an extended spectrum of nocturnal disabilities and easier use for patients, is a reliable, valid, precise, and potentially treatment-responsive tool for measuring sleep disorders in PD.