Age related changes in sleep quantitative EEG brain activity and longitudinal relationship to cognitive function

Abstract

Introduction

Sleep microarchitecture including spindle characteristics evolves with normal ageing, and cognition declines with age. Sleep disturbance is a risk factor for cognitive impairment; however, the underlying pathophysiology remains incompletely understood. Altered sleep spindle metrics have been shown to be associated with an increased risk of MCI in cross-sectional studies, however the longitudinal relationship between sleep neurophysiology and cognition is unclear. This study examined sleep microarchitecture measured by single channel (F4-M1) EEG and cognitive performance assessed with the TMT and MMSE in a cohort of community dwelling men from the FAMAS over an 8-year period.

Objectives

1.

Examine changes in sleep microarchitecture, and changes in cognition, over 8 years.

2.

Investigate the longitudinal relationship between sleep microarchitecture and cognition.

Methodology

Participants from the FAMAS with no reported diagnosis of OSA underwent home-based PSG and cognitive testing at baseline and at follow-up, approximately 8 years apart. Power spectral analysis of EEG recordings was performed. Baseline and follow-up sleep parameters including sleep spindle characteristics, and baseline and follow-up cognition were compared using paired t-tests, and associations were examined with Pearson’s correlation.

Results

NREM (267.6 vs 299.2 minutes) sleep was higher during follow up PSG compared to baseline (p < .001). NREM spindle events (257.5 vs 351.7) and density (0.95 vs 1.17 events/ minute) were higher at follow up (p < .001). TMT performance declined (TMT-A: 15.4 vs. 38.7 seconds, TMT-B: 74.9 vs. 93.7 seconds, p <.001). There was no change in MMSE. The changes in sleep spindle metrics and cognition were not correlated.

Conclusions

In this cohort, significant differences were observed in sleep spindle metrics and cognitive function at follow-up compared to baseline. No longitudinal relationship between sleep microarchitecture and cognition was observed.