Associations among sleep quality, cognitive decline, and Alzheimer's disease pathology in older adults: A longitudinal study

INTRODUCTION: This study aimed to investigate whether sleep quality predicts cognitive/functional decline, and whether Alzheimer's disease (AD) pathology modifies these relationships. METHODS: The Pittsburgh Sleep Quality Index was administered to 326 older adults (113 cognitively normal, 192 mild cognitive impairment, 21 dementia; mean age = 66.4 ± 8.0 years) enrolled in the 1Florida Alzheimer's Disease Research Center. The Clinical Dementia Rating Sum of Boxes (CDR-SB) assessed cognitive/functional decline at baseline and over time. Moderators included hippocampal volume (HV), amyloid beta (Aβ) positron emission tomography, and plasma phosphorylated tau (p-tau)217. RESULTS: Cross-sectionally, longer sleep duration and later wake time were associated with worse CDR-SB, with stronger associations observed among individuals with higher Aβ and p-tau217 levels, and smaller HV. Longitudinally, prolonged sleep duration was associated with faster cognitive decline, particularly in individuals with elevated Aβ or p-tau217 levels and smaller hippocampal volumes at baseline. DISCUSSION: Prolonged sleep duration and later wake times predicted worsening cognitive performance, and these effects were strengthened by greater AD pathology.