Sleep Disorders in Mild Cognitive Impairment

Abstract

Background: Previous studies have indicated that sleep disorders can be observed in patients with higher risk of progression to Alzheimer's disease (AD). Importantly, the relationship between cerebrospinal fluid (CSF) biomarkers for AD and objective sleep parameters in patients with Mild Cognitive Impairment (MCI) has not been studied. The aim of the present study was to analyze the relationship between objective and subjective sleep parameters and CSFAD-biomarkers in patients with MCI. Methods: Sixty-three patients (mean age=66.70; SD=7.88) with MCI were included in the study. Sleep subjective parameters were assessed by medical interview (tiredness during day, nocturnal awakening, excessive daytime sleepiness, nap, nod off and awakening accompanied by shortness of breath) and an overnight polysomnography recording were used to assess objective parameters (apnea/hypopnea index, total sleep time, sleep efficiency, sleep latency, arousal index, awakening, stage 1, 2 and slow wave sleep and REMsleep, number of stage shifts, periodic limb movement index, O2 saturation during sleep and wake time after sleep onset index). Phosphorylated-tau (P-Tau), total-tau (T-Tau) and amyloid beta 42 (Aβ42) were measured in CSF. Results: Regression analyses without covariates showed that higher apnea/hypopnea index was related to higher P-Tau and T-Tau and to lower Aβ42 levels (all p<0.025). Importantly, after adjusting for potential cofounders (i.e., age, sex, Body Mass Index, sleep medication, smoking, hypertension, cardiovascular and cerebrovascular diseases), higher apnea/hypopnea index was related to higher P-Tau (β=0.304, p=0.012) and T-Tau (β=0.350, p=0.003), but not to Aβ42 (β=-0.170, p=0.163). None of the other relationship between CSF and subjective and objective sleep parameters were statistically significant (p>0.126). Conclusions: Our results indicate that there is an association between subclinical apnea/hypopnea and AD-related neuronal injury biomarkers (i.e., P-Tau and T-Tau). These findings suggest that apnea/hypopnea may be associated with the development of AD in patients with MCI.