Polysomnography, brain volumetry, and mismatch negativity as early biomarkers of amnestic mild cognitive impairment progression

Background: Mild cognitive impairment (MCI) is a heterogenous disorder in which a proportion of patients follow stationary or regressive courses while others undergo clinical progression to dementia. Methods: This study was conducted on 60 amnestic mild cognitive impairment (amMCI) and 20 healthy control subjects submitted to baseline Montreal Cognitive Assessment (MoCA) scale, one-night polysomnography (PSG), hippocampal/entorhinal cortex (HPC/ERC) MRI volumetry, and auditory mismatch negativity (MMN). Fifty-six amMCI subjects continued the study and underwent follow-up MoCA scale 1 year after their baseline evaluation, 17 showed amMCI progression (≥ 3 points decrease in MoCA scale), and 39 had stationary or regressive courses. Results: Progressive amMCI patients showed reduced sleep efficiency and shortened rapid eye movement (REM) sleep in PSG, decreased HPC/ERC–MRI volumetry and reduced amplitudes with delayed latencies of the MMN evoked potentials. Conclusions: PSG shortened REM sleep, MRI–HPC/ERC volumes reduction, and low amplitude delayed auditory MMN are valuable non-invasive screening predictors of amMCI progression.