To compare sleep and autonomic profiles in drug-naïve PD and MSA patients and to characterize disease-specific associations between these domains.

A retrospective sample of 136 drug-naïve PD and 67 MSA patients underwent overnight polysomnography (PSG) and autonomic evaluation, including autonomic function testing (AFT) and cardiac [I-123] MIBG scintigraphy. Group comparisons were performed for sleep and autonomic parameters. Variables showing significant associations and intergroup differences in Spearman correlation analyses were subsequently entered into structural equation models (SEM) to explore latent relationships.

The PD group was older than the MSA group, with no differences in sex, disease duration, or autonomic-related comorbidities. In MSA patients, PSG revealed reduced stage N3 sleep and higher apnea-hyponea index (AHI), periodic limb movement index (PLMI), and arousal index. Cardiac MIBG uptake was more reduced in PD. Autonomic testing in MSA showed greater blood pressure drop during head-up tilt and higher Composite Autonomic Severity Score (CASS), except for the cardiovagal subscore. SEM in MSA demonstrated a significant negative path from autonomic dysfunction to sleep parameters, indicating that greater autonomic impairment was associated with poorer sleep quality. A marginal covariance between autonomic and sleep constructs suggested a potential interrelationship rather than a strictly unidirectional effect.

In MSA, both autonomic and sleep parameters were significantly more impaired than in PD. SEM further indicated that these domains are closely linked, whereby greater autonomic dysfunction is associated with poorer sleep quality. This interrelationship highlights the need for integrated management strategies addressing both domains.