Bright Light Therapy for Non-motor Symptoms in Parkinson's Disease

Inclusion criteria

• Diagnosis of idiopathic PD as defined by the United Kingdom PD Society Brain Bank Criteria
• PD Hoehn and Yahr stage 2-4
• Pittsburgh Sleep Quality Index (PSQI) score ≥ 5
• Treatment with levodopa and/or dopamine agonist; adjunctive PD medications will be allowed
• Stable dose of PD medications for at least 4 weeks prior to the study screening.

Exclusion criteria

• Atypical or secondary forms of parkinsonism
• Co-existent significant sleep apnea (as assessed by polysomnography- derived apnea/hypopnea index ≥15 events/hr of sleep)
• Co-existent restless legs syndrome (RLS), as assessed by the International Classification of Sleep Disorders (ICDS) diagnostic criteria for RLS
• Cognitive impairment as determined by the Mini-Mental State Examination (MMSE) score of ≤ 26
• Presence of depression defined as the Beck Depression Inventory (BDI) score >14
• Untreated hallucinations or psychosis (drug-induced or spontaneous)
• Use of hypno-sedative drugs for sleep or stimulants; participants will be allowed to taper these drugs and will become eligible 4 weeks after the taper is completed
• Use of Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs) antidepressants, unless the participant has been on a stable dose for at least 3 months prior to the screening
• Use of medications known to affect melatonin secretion, such as lithium, alpha- and beta-adrenergic antagonists
• Shift work, currently or within the prior 3 months
• Travel through ≥ 2 time zones within 60 days prior to study screening
• Hematocrit <32 mm3
• Pre-existing glaucoma/retinal disease contraindicated for light therapy (LT)
• Dense cataracts
• Use of medications known to photosensitize retinal tissue (phenothiazines, chloroquine, amiodarone, St. John's Wort)
• Unstable/serious medical illness.
• Pregnancy