Is shorter sleep linked to faster brain atrophy?

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Researchers asked whether short sleep, often held to cause poorer brain health, is associated with higher rates of structural brain decline. They analyzed 8,153 longitudinal MRI scans from 3,893 healthy adults and found no evidence of an association between sleep duration and brain atrophy.

In contrast, cross-sectional analyses of 51,295 observations showed inverse U-shaped relationships: 6.5 hours of sleep (95% confidence interval: 5.7–7.3 hours) was associated with the thickest cortex and largest brain volumes relative to intracranial volume. This finding fits converging evidence from mortality, health and cognition research linking roughly seven hours of sleep with good health.

Genome-wide association analyses suggested that genes associated with longer sleep in below-average sleepers were linked to shorter sleep in above-average sleepers. Mendelian randomization found no evidence of causal impacts of sleep on brain structure. Together, the results challenge the idea that habitual short sleep causes brain atrophy and suggest that normal brains promote adequate sleep duration, shorter than current recommendations.