The effects of bright light therapy on depression and sleep disturbances in patients with Parkinson's disease: a systematic review and meta-analysis of randomized controlled trials

Background: Depression and sleep disturbance are well-recognized non-motor features in patients with Parkinson's disease (PD). This meta-analysis aimed to explore the potential role of bright light therapy (BLT) in depression and sleep disturbances in Parkinson's Disease (PD). Methods: Four databases were independently searched by two reviewers: PubMed, Cochrane, Web of Science and Embase until February 2021. We evaluated the following depression related scales: Beck's Depression Inventory (BDI); the Geriatric Depression Rating Scale, 30-item (GDS-30); the Hamilton Depression Rating Scale (HDRS); the Hospital Anxiety and Depression Scale (HADS); the Epworth sleepiness scale (ESS); the Fatigue Severity Scale (FSS); the Pittsburgh sleep quality index (PSQI); the Parkinson's disease sleep scale (PDSS); Scales for Outcomes in Parkinson's disease Sleep Scale (SCOPA) and the Insomnia severity index (ISI) to access the effects of bright light therapy on depression and sleep disturbances in patients with PD. Effect size (standardized mean deviation [SMD] and 95% confidence interval [CI]) were used to analyze the continuous results data of intervention group and control light group. Data from five randomized, controlled trials totaling 173 patients with PD was included. Results: BLT significantly improved depression symptoms (BDI, GDS-30, HDRS and HADS) of PD patients (0.34, 95% CI = 0.06-0.61). Insomnia symptoms (SCOPA and ISI) for patients with PD were significantly improved by BLT as well (1.15, 95% CI = 0.71-1.60). Whereas, no difference was observed in the control light group in improving the depression or insomnia symptoms of PD patients. Conclusion: BLT is an effective intervention for improving depressive symptoms and sleep disturbances in patients with PD. (C) 2021 Elsevier B.V. All rights reserved.