RESEARCH – October 2018

Sleep disorders in patients with Parkinson’s disease: validation of the Parkinson’s Disease Sleep Scale 2nd version in Estonian

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Introduction. Non-motor features of Parkinson’s disease (PD) include several nocturnal disturbances. There are different questionnaires for assessing sleep disorders in patients with PD. The Parkinson’s Disease Sleep Scale 2nd version (PDSS-2) has been widely used since 2010. The aim of this pilot study was to linguistically validate the scale and to test it among Estonian speaking PD patients.

Methods. The study consisted of two parts: the PDSS-2 validation process in accordance with the Mapi Research Trust guidelines, and subsequent testing of the translated version of the PDSS-2 in patients. For this study, we recruited 39 patients with previously diagnosed PD who were all native Estonian speakers. In addition to sleep disturbances, we evaluated severity of the disease (based on the Movement Disorders Society Unified Parkinson’s Disease Rating Scale, Schwab and England Activities of Daily Living Scale and Hoehn and Yahr staging), depression (based on the Beck Depression Inventory), patients’ cognitive status (based on Mini Mental State Examination) and quality of life (based on the 39-item Parkinson’s Disease Questionnaire).

Results. The median duration of patients’ sleep was 7.0 (3.5–14) hours. The PDSS-2 average total score was 13 (0–37) points out of 60 (higher score indicated greater burden of nocturnal disturbances). The PDSS-2 score correlated negatively with duration of sleep; and positively with declined cognitive status, reduced quality of life, depression and severity of PD. According to linear regression analysis, the main factors determining PDSS-2 total score were duration of sleep, depression, quality of life and other non-motor features of PD.

Conclusion. Sleep disorders are widespread in Estonian patients with PD, correlating with depression, declined cognition, and