Alzheimer's Imaging Consortium.

Area of Science:

• Gerontology
• Neuroscience
• Biomarkers

Background:

• Sleep disturbances are linked to Alzheimer disease (AD) pathology and cognitive decline.
• Longitudinal studies combining sleep, AD biomarkers, and cognition are scarce.
• Understanding sleep changes in aging individuals with and without AD pathology is vital for future research design.

Purpose of the Study:

• To assess the longitudinal reliability of various sleep measures in older adults with and without amyloid positivity.
• To determine the most reliable sleep metrics for future aging and AD research.
• To estimate sample sizes needed for longitudinal observational studies.

Main Methods:

• Longitudinal assessment of sleep over ~3.5 years using self-reports and at-home electroencephalography (EEG).
• Amyloid PET imaging and cognitive assessments were conducted longitudinally.
• Test-retest reliability was measured using intraclass correlation coefficients (ICC); power analysis estimated sample sizes.

Main Results:

• EEG-derived spectral power measures exhibited the highest test-retest reliability, followed by EEG sleep staging/duration, and then self-reported sleep.
• Spectral power measures required the smallest sample sizes for detecting longitudinal changes.
• Factor analysis identified five distinct sleep factors from the collected data.

Conclusions:

• Objective EEG measures offer the greatest reliability for assessing sleep changes over time in older adults, irrespective of amyloid status.
• These findings are essential for optimizing the design of future longitudinal studies investigating the sleep-AD relationship.