A new longitudinal study found that sleeping too long and waking up late are linked to faster cognitive and functional decline in older adults — and those effects are amplified in people with biological markers of Alzheimer's disease. Using the Pittsburgh Sleep Quality Index across 326 older adults, researchers tracked cognitive decline over time using the Clinical Dementia Rating Sum of Boxes. Crucially, the harmful relationship between extended sleep and worsening cognition was strongest in individuals with high amyloid beta, elevated phosphorylated tau-217, and reduced hippocampal volume. The findings challenge the assumption that more sleep is always protective and suggest that prolonged sleep may be a symptom or accelerant of underlying neurodegeneration rather than a remedy.
