Sleep disturbances in patients with Parkinson's disease (PD) are common but frequently under recognized and ineffectively treated. Depression is also a common cause of sleep problems in the elderly. Both are important factors for health and quality of life and interact with many medical conditions.

The aim of this study was to examine the associations between disease severity, sleep-related problems, severity of depression, and quality of life in a sample of PD patients taking dopamine antagonists.

Fifty-two patients with PD included in the study. During the trial, patients were examined two times. At the first follow-up, all patients were classified according to the Hoehn and Yahr (H-Y) classification. At the second follow-up within 1 month, each patient underwent diagnostic evaluation by a trained psychiatrist using a detailed assessment battery including Parkinson's disease Sleep Scale, Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, Parkinson's disease Quality of Life Questionnaire, and Beck Depression Inventory. Patients with clinical signs of dementia were not included in this study.

Severity of depressive symptoms was significantly correlated with subjective sleep troubles in PD patients. Moreover, severity of sleep problems and to a lesser degree depression contributed significantly to the overall variance in quality of life.

Depression and troubled sleep were associated with poor quality of life in patients with PD. It is important to examine for the presence of sleep disorders and depression in PD, because recognition of these conditions may become an important part of treatment of PD.