Mediating role of obstructive sleep apnea in altering slow-wave activity and elevating Alzheimer's disease risk: Pilot study from a northern Taiwan cohort.

Objectives: Obstructive sleep apnea is associated with alterations in slow-wave activity during sleep, potentially increasing the risk of Alzheimer's disease. This study investigated the associations between obstructive sleep apnea manifestations such as respiratory events, hypoxia, arousal, slow-wave patterns, and neurochemical biomarker levels.

Methods: Individuals with suspected obstructive sleep apnea underwent polysomnography. Sleep disorder indices, oxygen metrics, and slow-wave activity data were obtained from the polysomnography, and blood samples were taken the following morning to determine the plasma levels of total tau (T-Tau) and amyloid beta-peptide 42 (Aβ) by using an ultrasensitive immunomagnetic reduction assay. Subsequently, the participants were categorized into groups with low and high Alzheimer's disease risk on the basis of their computed product Aβ × T-Tau. Intergroup differences and the associations and mediation effects between sleep-related parameters and neurochemical biomarkers were analyzed.

Results: Forty-two participants were enrolled, with 21 assigned to each of the low- and high-risk groups. High-risk individuals had a higher apnea-hypopnea index, oxygen desaturation index (≥3%, ODI-3%), fraction of total sleep time with oxygen desaturation (SpO90% ), and arousal index and greater peak-to-peak amplitude and slope in slow-wave activity, with a correspondingly shorter duration, than did low-risk individuals. Furthermore, indices such as the apnea-hypopnea index, ODI-3% and SpO90% were found to indirectly affect slow-wave activity, thereby raising the Aβ × T-Tau level.

Conclusions: Obstructive sleep apnea manifestations, such as respiratory events and hypoxia, may influence slow-wave sleep activity (functioning as intermediaries) and may be linked to elevated neurochemical biomarker levels. However, a longitudinal study is necessary to determine causal relationships among these factors.

Statement Of Significance: This research aims to bridge gaps in understanding how obstructive sleep apnea is associated with an elevated risk of Alzheimer's disease, providing valuable knowledge for sleep and cognitive health.