Biomarkers.

Area of Science:

• Neuroscience
• Gerontology
• Sleep Medicine

Background:

• Sleep disturbances are linked to Alzheimer disease (AD) pathology and cognitive decline.
• Longitudinal studies correlating sleep, AD biomarkers, and cognition are scarce.
• Understanding sleep changes in aging is crucial for AD 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 inform sample size calculations for longitudinal observational studies.

Main Methods:

• Longitudinal sleep assessment using self-reports and at-home electroencephalography (EEG) over ~3.5 years.
• Amyloid PET imaging and cognitive assessments were conducted longitudinally.
• Test-retest reliability (ICC) and power analysis were used to evaluate sleep metrics.

Main Results:

• EEG-derived spectral power demonstrated the highest test-retest reliability, followed by sleep staging and duration.
• Self-reported sleep measures showed lower reliability compared to objective EEG measures.
• Spectral power measures require smaller sample sizes for detecting longitudinal changes.

Conclusions:

• Objective EEG measures, particularly spectral power, are highly reliable for tracking sleep changes in older adults.
• These findings are vital for designing future longitudinal studies on sleep and Alzheimer disease.
• Reliable sleep metrics enhance the power of studies investigating the relationship between sleep and AD progression.