Disrupted sleep and alertness impact as many as 90% of people with Parkinson's disease and contribute to a poorer quality of life and impaired mood and cognition. The circadian system plays a critical role in the regulation of sleep and alertness and is most effectively synchronized by light. A previous clinical trial suggested potential beneficial effects of bright light therapy on sleep in individuals with Parkinson's disease. This study investigated the relationship between frequency of light therapy treatments and participant adherence, tolerability, and effectiveness in reducing sleep problems and improving quality of life.
