Alzheimer's Imaging Consortium

Area of Science:

• Neuroscience
• Gerontology
• Sleep Science

Background:

• Sleep fragmentation and irregularity are linked to cognitive decline in older adults.
• Cognitive deficits in aging are associated with reduced brain volumes, particularly cortical gray matter and hippocampus.
• The interplay between sleep, brain structure, and cognition in older adults is not fully understood.

Purpose of the Study:

• To investigate the bidirectional mediation effects of sleep patterns and brain volume on cognitive performance.
• To explore how sleep regularity, fragmentation, and brain structure influence cognitive functions in community-dwelling older adults.

Main Methods:

• Utilized data from the SG70 study, including sleep data from Oura rings and neurocognitive assessments from 800 older adults.
• Employed partial least squares correlation (PLSC) to identify sleep profiles associated with cognitive performance.
• Conducted mediation analyses on a subset of 467 participants with MRI data to examine the bidirectional influence of sleep and brain volumes (cortical gray matter, hippocampus) on cognition.

Main Results:

• A sleep profile characterized by high regularity and low fragmentation was significantly associated with better cognitive performance.
• Brain volume partially mediated the relationship between sleep and cognition.
• Sleep partially mediated the relationship between brain volume and cognition, indicating a bidirectional influence.

Conclusions:

• A bidirectional, though small, mediation effect exists between brain volume and sleep in influencing cognition.
• Gray matter atrophy and irregular/fragmented sleep interact to negatively impact cognitive function in older adults.