Orthostatic hypotension and acute cognitive dysfunction in Parkinson's disease: insights from functional...

To examine short-term associations among position-dependent executive performance and cerebral hemodynamic changes using functional near-infrared spectroscopy (fNIRS) in participants with Parkinson's disease (PD) with and without orthostatic hypotension (OH).

Twenty-nine nondemented participants with PD (19 without OH (OH-), 10 with OH (OH+)) completed a verbal fluency test (VFT) in supine and upright positions on a tilt table, while their cerebral oxygenation was continuously monitored using a full-head fNIRS system. Age-adjusted ANCOVA examined the interaction effects of OH status and position on VFT scores, while linear mixed-effects models assessed changes in oxygenated (HbO) and deoxygenated hemoglobin (HbR) within the dorsolateral prefrontal cortex (DLPFC).

A significant interaction between OH status and position emerged for letter fluency (p = 0.043, η_p² = 0.148), with the OH+ group demonstrating poorer performance and more errors while upright. fNIRS analyses revealed that OH+ participants exhibited reduced HbR in both left (p = 0.010, d = 0.73, 95% CI: [0.19, 1.27]) and right DLPFC (p = 0.011, d = 0.73, 95% CI: [0.19, 1.27]) when upright, suggesting increased utilization of cognitive resources. No participants reported orthostatic symptoms during the cognitive task.

Despite lack of OH symptomatology, PD OH+ individuals demonstrated impaired cerebral hemodynamic regulation when upright, which was associated with poorer cognitive performance.

fNIRS-derived measures for monitoring cerebral hemodynamics in patients with autonomic failure may provide a clinically relevant indicator of postural changes in brain dysfunction.