Abstract
Previous studies have demonstrated that sleep-breathing disorders, and especially obstructive sleep apnea (OSA), can be observed in patients with higher risk of progression to Alzheimer’s disease (AD). Recent evidence indicates that cerebrospinal fluid (CSF) AD-biomarkers are associated with OSA. In this study, we investigated these associations in a sample of patients with Mild Cognitive Impairment (MCI), a condition that is considered the first clinical phase of AD, when patients showed biomarkers consistent with AD pathology. Fifty-seven patients (mean age=66.19; SD=7.13) with MCI were included in the study. An overnight polysomnography recording was used to assess objective sleep parameters (i.e., Apnea/hypopnea index, total sleep time, sleep efficiency, sleep latency, arousal index, awakening, stage 1, 2, and slow wave sleep and REM sleep, periodic limb movement index, O2 saturation during sleep, and percentage of time O2 saturation <90%). Phosphorylated-tau (P-tau), total-tau (T-tau) and amyloid beta 42 (Aβ42) were measured in CSF. Unadjusted correlation analyses showed that a higher apnea/hypopnea index (reflecting higher OSA severity) was related to higher P-tau and T-tau (both results remained significant after Bonferroni correction, p=0.001). Importantly, these associations were observed even after adjusting for potential confounders (i.e., age, sex, Body Mass Index, sleep medication, smoking, hypertension, and heart disease). Although more research is needed to establish a causal link, our findings provide evidence that OSA could be related to the pathophysiological mechanisms involved in neurodegeneration in MCI patients.
