Natural Age-Related Slow-Wave Sleep Alterations Onset Prematurely in the Tg2576 Mouse Model of Alzheimer's Disease.

Introduction: Sleep insufficiency or decreased quality have been associated with Alzheimer's disease (AD) already in its preclinical stages. Whether such traits are also present in rodent models of the disease has been poorly addressed, somewhat disabling the preclinical exploration of sleep-based therapeutic interventions for AD.

Methods: We investigated age-dependent sleep-wake phenotype of a widely used mouse model of AD, the Tg2576 line. We implanted electroencephalography/electromyography headpieces into 6-month-old (plaque-free, n = 10) and 11-month-old (moderate plaque-burdened, n = 10) Tg2576 mice and age-matched wild-type (WT, 6 months old n = 10, 11 months old n = 10) mice and recorded vigilance states for 24 h.

Results: Tg2576 mice exhibited significantly increased wakefulness and decreased non-rapid eye movement sleep over a 24-h period compared to WT mice at 6 but not at 11 months of age. Concomitantly, power in the delta frequency was decreased in 6-month old Tg2576 mice in comparison to age-matched WT controls, rendering a reduced slow-wave energy phenotype in the young mutants. Lack of genotype-related differences over 24 h in the overall sleep-wake phenotype at 11 months of age appears to be the result of changes in sleep-wake characteristics accompanying the healthy aging of WT mice.

Conclusion: Therefore, our results indicate that at the plaque-free disease stage, diminished sleep quality is present in Tg2576 mice which resembles aged healthy controls, suggesting an early-onset of sleep-wake deterioration in murine AD. Whether such disturbances in the natural patterns of sleep could in turn worsen disease progression warrants further exploration.