Variability in objective sleep is associated with Alzheimer's pathology and cognition

Area of Science:

• Neuroscience
• Sleep Medicine
• Gerontology

Background:

• Sleep duration and efficiency are linked to Alzheimer's disease (AD) risk.
• Traditional studies often overlook sleep variability, focusing on average measures from self-reports.
• Objective sleep measures are crucial for understanding sleep's role in AD pathology.

Purpose of the Study:

• To investigate the association between intra-individual variability in objective sleep duration and efficiency with AD biomarkers (amyloid-beta and tau).
• To examine the relationship between sleep variability and cognitive function in older adults with early mild cognitive impairment.
• To explore the modifying effects of apolipoprotein E4 status on these associations.

Main Methods:

• Cross-sectional study of 52 older adults with early mild cognitive impairment.
• Objective sleep measures (duration, efficiency) assessed using accelerometry.
• In vivo AD pathology evaluated via positron emission tomography imaging for amyloid-beta and tau.
• Cognitive function assessed across multiple domains (memory, executive function).

Main Results:

• Less variability in sleep duration was associated with lower amyloid-beta burden, higher global cognition, and better inhibitory control.
• Less variability in sleep efficiency correlated with lower amyloid-beta burden and higher global cognition.
• Longer sleep duration was linked to better visual memory and inhibitory control.
• Apolipoprotein E4 status modified associations, with less sleep efficiency variability and longer sleep duration showing greater protective effects against amyloid-beta in carriers.

Conclusions:

• Lower intra-individual variability in sleep duration and efficiency, alongside longer mean sleep duration, are associated with reduced amyloid-beta pathology and improved cognition.
• Sleep consistency and duration may be particularly protective against amyloid-beta burden in apolipoprotein E4 carriers.
• Further longitudinal and intervention studies are needed to confirm causality and inform targeted sleep interventions for AD prevention.