Respiratory event-related physiological biomarkers and cognitive performance in obstructive sleep apnoea

Individuals with obstructive sleep apnoea (OSA) are at increased risk of cognitive impairment. However, the physiological mechanisms that link OSA to this impairment are unclear. We assessed the association between novel physiological biomarkers (i.e. respiratory event-related electroencephalography (EEG) activity and autonomic responses) and the risk of cognitive impairment.

Participants with OSA (apnoea-hypopnoea index ≥5 events·h^-1) from the Canadian Sleep and Circadian Network observational cohort were studied. Brain Response to Event (BReTE) was derived from EEG power (defined as mean (median post-event power/median pre-event power) (frequency range: 0.5-50 Hz)) for each individual. Event-related autonomic responses were measured by heart rate response to events (ΔHR: the difference between maximum post-event heart rate and minimum heart rate during event) and photoplethysmography (PPG)-derived vasoconstriction activity (event-related area and depth of PPG decline). Cognitive performance was assessed using the Montreal Cognitive Assessment (MoCA), Wechsler Digit Symbol Coding (DSC) and Rey Auditory Verbal Learning Test-Delayed Recall (RAVLT-DR). Multiple logistic regression examined the independent associations between biomarkers and outcomes.

We studied 537 individuals (42% female) with a median age of 55 years. In fully adjusted models, each 1sd decrease in BReTE was associated with higher odds of poor cognitive performance indicated by MoCA <26 (OR 1.42, 95% CI 1.13-1.79; p=0.003), DSC <25th percentile (OR 1.35, 95% CI 1.02-1.84; p=0.04) and RAVLT-DR <25th percentile (OR 1.50, 95% CI 1.13-2.02; p=0.007). Additionally, those with low ΔHR compared to the mid-range group were at increased risk of poor cognitive performance. Vasoconstriction indices were not associated with cognitive performance.

Blunted EEG and heart rate responses to respiratory events are linked to poorer cognitive performance in OSA, highlighting the value of EEG in identifying individuals at risk for cognitive impairment.