Examining the association between sleep apnea and total hippocampal volumes in cognitive impairment

The prevalence of dementia is rising due to an aging population. Given the known risks of obstructive sleep apnea (OSA) on cerebrovascular health, we hypothesized that markers of OSA would correlate with reduced hippocampal volumes in individuals with cognitive impairment due to neurodegenerative, vascular, or mixed (NVM) etiologies.

Data from 166 patients were retrospectively analyzed. Participants underwent polysomnography or home sleep apnea tests, alongside structural brain magnetic resonance imaging (MRI). They were categorized into cognitive impairment due to NVM etiology or subjective cognitive complaints. Multiple linear regression models examined correlations between sleep variables and hippocampal volume.

The presence of OSA, time under 90% oxygen saturation, and mean SpO₂ were significantly associated with reduced hippocampal volumes in the NVM group, but not the subjective cognitive complaints.

These findings suggest that individuals with cognitive impairment due to NVM etiology experience underlying neurodegenerative processes, which increase susceptibility to the adverse effects of OSA.

Hypoxic burden, rather than AHI, was associated with hippocampal volume loss. The presence of OSA, T90%, and mean SpO₂ were linked with reduced hippocampal volume. Neurodegenerative and vascular processes may raise susceptibility to OSA harms.