Study Objectives: To evaluate the impact of sleep disorders on non-motor symptoms in patients with Parkinson disease (PD). Design: This was a cross-sectional study. Patients with PD were evaluated for obstructive sleep apnea (OSA), restless legs syndrome (RLS), periodic limb movement syndrome (PLMS), and REM sleep behavior disorder (RBD). Cognition was assessed with the Montreal Cognitive Assessment and patients completed self-reported questionnaires assessing non-motor symptoms including depressive symptoms, fatigue, sleep complaints, daytime sleepiness, and quality of life. Setting: Sleep laboratory. Participants: 86 patients with PD (mean age = 67.4 ± 8.8 years; range: 47-89; 29 women). Interventions: N/A. Measurements and Results: Having sleep disorders was a predictor of overall non-motor symptoms in PD (R 2 = 0.33, p < 0.001) while controlling for age, PD severity, and dopaminergic therapy. These analyses revealed that RBD (p = 0.006) and RLS (p = 0.014) were signifi cant predictors of increased non-motor symptoms, but OSA was not. More specifi cally, having a sleep disorder signifi cantly predicted sleep complaints (ΔR 2 = 0.13, p = 0.006), depressive symptoms (ΔR 2 = 0.01, p = 0.03), fatigue (ΔR 2 = 0.12, p = 0.007), poor quality of life (ΔR 2 = 0.13, p = 0.002), and cognitive decline (ΔR 2 = 0.09, p = 0.036). Additionally, increasing number of sleep disorders (0, 1, or ≥ 2 sleep disorders) was a signifi cant contributor to non-motor symptom impairment (R 2 = 0.28, p < 0.001). Conclusion: In this study of PD patients, presence of comorbid sleep disorders predicted more non-motor symptoms including increased sleep complaints, more depressive symptoms, lower quality of life, poorer cognition, and more fatigue. RBD and RLS were factors of overall increased non-motor symptoms, but OSA was not.
S C I E N T I F I C I N V E S T I G A T I O N SP arkinson disease (PD) is a progressive neurodegenerative disorder primarily characterized by motor symptoms and increasing motor-related disability, including bradykinesia, rigidity, and tremor.1 Non-motor symptoms (NMS) such as sleep dysfunction, sleepiness, fatigue, pain, and depressive symptoms, are common in PD. In a large multicenter study, NMS were reported by 99% of 1072 PD patients.2 The presentation of NMS in PD is highly variable, and the understanding of such heterogeneity in PD is limited and incomplete.3,4 Chaudhuri et al. 4 suggested that NMS dominate the clinical picture in patients with PD and contribute to the severe disability these patients experience, impair quality of life, and even shorten life expectancy. Studies have suggested that NMS, more than motor symptoms, may impact caregiver distress, quality of life, institutionalization rates, and overall costs related to PD .4-6 A 15-year follow-up study of patients with PD reported that the NMS that did not respond to dopamine therapy (e.g., dementia, sleep disruption) were "more disabling than endof-dose failure or dyskinesia" and were the major cause of morbidity and mortality. Sixty to 98% of pati...