Hypoxemia during rapid eye movement sleep mediates memory impairment in older adults at risk for dementia via CA1 hippocampal volume loss.
Level 4 - case-series / case-control
Cross-sectional observational study assessing mediation pathways between sleep indices, MRI volumetric measures, and cognitive performance.
PubMed 39302096 · doi:10.1111/ene.16491
What was done
Researchers evaluated 338 adults aged ≥50 years with subjective or mild cognitive impairment using clinical assessments, Rey Auditory Verbal Learning Test (RAVLT), overnight polysomnography to measure REM and non-REM 3% Oxygen Desaturation Index (ODI), and high-resolution hippocampal MRI (n = 135). Mediation analyses tested whether CA1, CA3, subiculum, or dentate gyrus volumes mediated the relationship between hypoxemia and verbal learning or memory.
What was found
REM-ODI showed no direct effect on verbal learning (p > 0.05) or memory (p > 0.05). Mediation analyses demonstrated a significant indirect effect of higher REM-ODI on poorer verbal learning (β = -0.09, 95% CI = -0.238 to -0.005) and poorer memory (β = -0.100, 95% CI = -0.255 to -0.005), mediated specifically by CA1 volume loss. No such associations were found for non-REM sleep (p > 0.05).
Why it matters
These findings suggest that nocturnal hypoxemia occurring specifically during REM sleep may contribute to cognitive impairment in at-risk older adults via localized CA1 hippocampal vulnerability.
Limits
The study is cross-sectional, precluding causal conclusions. MRI hippocampal subfield data were available for only a subset of the cohort (n = 135 of 338). Long-term clinical progression was not assessed.
Cited by
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