Biomarkers

Sleep disorders are common comorbid pathology in patients with Alzheimer's disease (AD). It is generally accepted that sleep disorders may be a risk factor for AD development due to increased Aβ deposition in the brain and may contribute to more rapid progression of cognitive deficit. Increased deposition of Aβ occurs mainly as a result of disruption of the glymphatic system, which functions most effectively during slow-wave sleep. The diffusion tensor images analysis along perivascular spaces (DTI-ALPS) method is used for indirect assessment of the glymphatic system. In our study we compare polysomnographic (PSG) findings, DTI-ALPS indices in AD and controls, and identify the relationship between these indicators.

The study included 2 groups: 7 patients with the amnestic variant of AD (6 females, mean age 69 years) and 7 cognitively intact volunteers (5 females, mean age 61 years). All participants underwent brain MRI with evaluation of DTI-ALPS indices, PSG with determination of sleep efficiency (SE) and sleep staging (N1, N2, N3, R).

A statistically significant decreased SE and the increased duration of stage N1 (%) in AD were revealed. A tendency to a decrease in the duration of stage N3 (%), DTI-ALPS indices in AD is also noted, however statistically insignificant (Table 1). A correlation analysis of MRI and PSG findings revealed a significant inverse relationship between the right DTI-ALPS index and the duration of stage N1 (%) (p = 0.016*), between the left DTI-ALPS index and the duration of stage N2 (%) (p = 0.027*). Additionally, we found a tendency to a moderate direct relationship between the duration of stage N3 (%) and the right DTI-ALPS index (p = 0.089) as well as the left DTI-ALPS index (p = 0.081).

In AD patients the PSG findings of disturbed sleep were detected. The revealed correlations suggested possible relationship between altered sleep architecture and insufficient glymphatic system functioning in neurodegeneration that requires further study.