Age and orthostatic hypotension are associated with baroreflex sensitivity and cerebral oxygenation after postural change.

Baroreflex sensitivity (BRS), maintaining blood pressure (BP), and cerebral autoregulation, maintaining cerebral blood flow (CBF), are regulatory mechanisms to counteract posture-related BP changes and their effect on CBF. These mechanisms may fail in geriatric conditions such as orthostatic hypotension (OH) and cause symptoms and falls. This study aimed to determine the association of age, sex, antihypertensive use, comorbidity, and OH with BRS and cerebral oxygenation after postural change. Thirty-four younger adults (median age 25 years), 30 older adults (median age 77 years), and 41 geriatric outpatients (median age 76 years) performed 2-3 supine-stand transitions, while heart rate (electrocardiogram), BP (volume-clamp photoplethysmography), and cerebral oxygenation (near-infrared spectroscopy) were measured continuously. BRS, cerebral oxygenation and cerebral autoregulation were determined in the time and frequency domain. Associations were investigated using linear regression and group comparisons. Higher age and presence of OH (OH in at least one supine-stand transition during a continuous BP measurement) were associated with lower BRS (1 % per year, 30 % when having OH). Higher age was associated with higher cerebral oxygenation recovery (0.1 μmol/L per year) after 30 s, while OH was associated with lower cerebral oxygenation recovery (1.3 μmol/L when having OH) at 1 min after postural change. No evidence of cerebral autoregulation impairment was found across all three groups. Reduced BRS and cerebral oxygenation recovery specifically in participants with OH are in line with their assumed susceptibility to cerebral hypoxia. The role of cerebral autoregulation as a compensatory mechanism for failing BRS could not be confirmed.