Exploring the intersection between orthostatic hypotension and daytime sleepiness in Parkinson's disease.

Introduction: Daytime sleepiness, reported in about 50 % of patients with Parkinson's disease (PD), is associated with high morbidity, poor quality of life and increased risk for accidents. While an association between dysautonomia and daytime sleepiness in early, de-novo PD has been reported, our understanding of the role of medications, cognitive status and co-morbidites on this relationship is inadequate.

Methods: Data were analyzed from the prospective Cincinnati Cohort Biomarkers Program. The primary outcome of interest was excessive daytime sleepiness (EDS), as measured by the Epworth Sleepiness Scale (ESS; ESS score > 10). The primary exposure variable was orthostatic hypotension (OH). Linear and logistic regression analyses followed by moderated graphical network analyses were conducted to explore the complex association between OH and ESS. Edge weight from graphical network analysis indicates the strength of the association.

Results: Data on 453 subjects with PD were analyzed. Median disease duration was 5.8 years and nearly 90 % were H&Y stage <3. OH was not associated with EDS. OH was associated with depression (edge weight, 0.22) in cognitively impaired patients but not in cognitively normal patients. In addition, depression was associated with ESS (edge weight, 0.37; moderation weight, 0.22) in cognitively impaired patients to a greater extent than in cognitively normal patients (edge weight, 0.22).

Conclusions: OH is not directly associated with daytime sleepiness in early, treated PD. However, OH seems to be associated with ESS via depression in cognitively impaired patients. This complex relationship deserves additional study.