# The impact of bright light therapy on non-motor symptoms in patients with Parkinson’s disease: a systematic review and meta-analysis

## TL;DR

Bright light therapy improves nighttime sleep in Parkinson’s patients but does not significantly help with other non-motor symptoms like depression or anxiety.

## Contribution

This study provides a meta-analysis of bright light therapy’s effects on non-motor symptoms in Parkinson’s disease, identifying its limited efficacy beyond sleep improvement.

## Key findings

- Bright light therapy improves nighttime sleep in Parkinson’s patients compared to dim light.
- Bright light therapy does not significantly improve depression, anxiety, cognition, or quality of life compared to dim light.
- The distance of the light source affects the therapy’s impact on sleep and daytime sleepiness.

## Abstract

The non-motor symptoms of Parkinson’s patients seriously affect their quality of life. This meta-analysis intended to systematically examine the beneficial effect of bright light therapy (BLT) on non-motor symptoms in individuals with Parkinson’s disease (PD).

A systematic search was conducted in PubMed, Cochrane Library, Web of Science, Embase, Ovid Medline, China National Knowledge Infrastructure (CNKI), WanFang VIP and CBM to comprehensively collect RCTS and NRCTS relevant to BLT for Parkinson’s disease. Data extraction and literature screening were carried out separately by two researchers, and used the RoB2 tool and ROBINS-I tool to evaluate the risk of bias for the two types of studies, respectively. Software such as RevMan5.4 and Stata 18.0 were used to analyze the data.

Compared with dim light, BLT has a considerable benefit in improving the nighttime sleep of people with Parkinson’s disease. However, its therapeutic effects on depression, anxiety, exhaustion, cognition, sleep quality and quality of life are not superior to those of dim light. Moreover, the distance of the light source will alter the therapeutic effect of BLT on nighttime sleep and daytime sleepiness.

Compared with dim light, BLT has a considerable benefit in improving the nighttime sleep of people with PD. However, its therapeutic effects on depression, anxiety, fatigue, cognition, sleep quality and quality of life are not superior to those of dim light. Moreover, the distance of the light source will alter the therapeutic effect of BLT on nighttime sleep and daytime sleepiness.

BLT can be used to treat the non-motor symptoms of PD and may become a practical option for home self-management. However, the ideal therapy parameters (such as intensity, distance, cycle, etc.) still need further research.

https://www.crd.york.ac.uk/PROSPERO/view/CRD420251047102, identifier (CRD420251047102).