No phenotypic or genotypic evidence for a link between sleep duration and brain atrophy

Area of Science:

• Neuroscience
• Sleep Science
• Medical Imaging

Background:

• Previous research suggested short sleep duration may lead to poorer brain health and structural decline.
• Understanding the relationship between sleep and brain structure is crucial for public health guidelines.

Purpose of the Study:

• To investigate the association between habitual sleep duration and brain structural decline in healthy adults.
• To determine if short sleep duration causally impacts brain structure.

Main Methods:

• Analysis of 8,153 longitudinal magnetic resonance imaging (MRI) scans from 3,893 healthy adults.
• Cross-sectional analyses of 51,295 observations to examine sleep duration and cortical thickness/brain volumes.
• Genome-wide association studies (GWAS) and Mendelian randomization to assess genetic predispositions and causality.

Main Results:

• No evidence was found linking habitual short sleep duration to increased brain atrophy in longitudinal analyses.
• Cross-sectional data revealed an inverse U-shaped relationship, with 6.5 hours of sleep associated with the thickest cortex and largest brain volumes.
• Mendelian randomization did not support a causal effect of sleep duration on brain structure.

Conclusions:

• The study challenges the hypothesis that habitual short sleep causes brain atrophy.
• Findings suggest that healthy brains may promote an adequate sleep duration, potentially shorter than currently recommended.
• Optimal sleep duration for brain health appears to be around 6.5 hours.