The role of polysomnography in Parkinson's disease: objective sleep assessment and clinical indications.

Sleep disorders (SDs) are highly prevalent in Parkinson's disease (PD), affecting up to 80% of patients during the disease and significantly contributing to impaired quality of life, cognitive decline, motor worsening, fall risk, and increased caregiver burden. Polysomnography (PSG) remains the gold standard for objective sleep assessment in PD and plays a central role in differential diagnosis and therapeutic planning. This review examines the spectrum of SDs identifiable by PSG, including rapid eye movement (REM) sleep behavior disorder (RBD), obstructive sleep apnea (OSA), periodic limb movements in sleep, and alterations in sleep architecture. Video-polysomnography (v-PSG) is essential for confirming REM sleep without atonia (RWA), which is the electrophysiological hallmark of RBD and a recognized prodromal marker of synucleinopathies. Also, PSG quantifies the apnea-hypopnea index (AHI), oxygen desaturation burden, and sleep fragmentation, parameters associated with cognitive impairment and disease progression. While home sleep apnea testing (HSAT, type 3) may be useful for selected cases with high suspicion of OSA, comprehensive in-laboratory (type 1) PSG provides superior diagnostic accuracy, particularly in patients with complex or overlapping sleep disturbances. Integrating objective sleep evaluation into routine PD management is crucial to identify treatable comorbidities, improve prognostic stratification, and optimize motor and non-motor outcomes.