Sleep Fragmentation and Sleep-Wake Cycle Dysregulation Are Associated with Cerebral Tau Burden in Patients with Mild Cognitive Impairment due to Alzheimer’s Disease: A Case Series

Background: Although disturbed sleep is frequent in patients with mild cognitive impairment (MCI) and dementia due to Alzheimer's disease (AD), the association between sleep and tau pathology is unclear. Objective: This case series focused on measuring the sleep-wake rhythm over 7 days through actigraphy in patients diagnosed with MCI due to AD. Further, the association between sleep-wake cycle and tau deposition measured through positron emission tomography (PET) was explored. Methods: This case series included 6 MCI due to AD patients (2 women and 4 men, mean age 73.17 +/- 5.53 years), who completed neuropsychological testing, 7-day actigraphy, and tau PET imaging with radiolabeled compounds aimed to estimate the density and distribution of aggregated tau neurofibrillary tangles in the brain. Results: The case series indicated that patients with MCI due to AD who exhibited greater tau deposition in the frontal, parietal, and limbic regions, as well as in the precuneus and olfactory regions, also showed increased sleep fragmentation, as measured through actigraphy. Conclusion: The findings from this case series suggest a potential link between tau deposition in key brain regions associated with AD and both sleep fragmentation and sleep-wake cycle dysregulation in a small sample of patients with MCI due to AD. These preliminary results warrant further investigation in larger, more comprehensive studies to confirm and expand upon these findings.