Natural age-related sleep-wake alterations onset prematurely in the Tg2576 mouse model of Alzheimer disease

Sleep insufficiency or decreased quality have been associated with Alzheimers 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. 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 months old (plaque-free, n=10) and 11 months old (moderate plaque-burdened, n=10) Tg2576 and age-matched wild-type (WT) mice and recorded vigilance states for 24 hours. Tg2576 mice exhibited significantly increased wakefulness and decreased non-rapid eye movement sleep over a 24-hour period compared to WT mice at 6, but not at 11 months of age. Concomitantly, delta power appeared decreased in 6-month old Tg2576 mice in comparison to age-matched WT controls, yielding a reduced slow-wave energy phenotype in the young mutants. Lack of genotype-related differences over 24 hours in overall sleep-wake phenotype at 11 months of age appears to be the result of the natural aging of WT mice. Therefore, our results indicate that at plaque-free stages of the disease, 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.