Biomarkers

Area of Science:

• Neuroscience
• Sleep Medicine
• Alzheimer's Disease Research

Background:

• Sleep's role in memory consolidation relies on the synchronized interaction of slow oscillations (SO), theta bursts, and spindles.
• Disrupted coupling of these sleep rhythms is observed in Alzheimer's disease (AD), but its progression and link to cognitive decline are unclear.

Purpose of the Study:

• To investigate the evolution of coupled sleep rhythm disruption across different stages of Alzheimer's disease (AD).
• To determine if disrupted sleep rhythms predict cognitive decline in individuals with AD.

Main Methods:

• Analysis of sleep electroencephalography (EEG), MRI, cerebrospinal fluid (CSF) AD biomarkers, and cognitive assessments in 93 participants.
• Populations included AD dementia (n=33), mild cognitive impairment (MCI) due to AD (n=38), and cognitively normal (CN; n=22).

Main Results:

• Coupled sleep rhythm disruption, specifically SO-theta burst and SO-spindle coupling, worsens with advancing AD stages (CN to MCI to AD dementia).
• Disruption is associated with APOE ε4 allele, amyloid and tau burden, and brain atrophy in the hippocampus and medial prefrontal cortex.
• Coupled sleep rhythm disruption predicts accelerated cognitive decline over two years.

Conclusions:

• The frequency and precision of coupled sleep oscillations decrease progressively during AD.
• These sleep rhythm changes are linked to cognitive decline over a 2-year period.
• Integrating sleep EEG with other biomarkers improves AD progression prediction.