Daily Relations Between Stress and Electroencephalography-Assessed Sleep: A 15-Day Intensive Longitudinal Design With Ecological Momentary Assessments

Abstract

Background: Recent studies have found bi-directional relations between stress and sleep. However, few studies have examined the daily associations between stress and electroencephalography (EEG) measured sleep.

Purpose: This study examined the temporal associations between repeated ecological momentary assessments of stress and EEG-estimated sleep.

Methods: Ninety-eight international or interstate undergraduate students (Mage = 20.54 ± 1.64, 76.5% female, 84.7% Asian) reported their stress levels four times daily at morning awakening, afternoon, evening, and pre-bedtime across 15 consecutive days (>4,000 total observations). Next-day stress was coded as an average of morning, afternoon, and evening stress. Z-Machine Insight+ recorded over 1,000 nights EEG total sleep time (TST), sleep onset latency, wake after sleep onset, sleep efficiency (SE), slow-wave sleep (SWS), and rapid eye movement (REM) sleep duration. Multilevel models, adjusted for covariates (i.e., sociodemographic, health factors, and daily covariates) and lagged outcomes, tested the daily within- and between-level stress-sleep associations.

Results: After adjusting for covariates, within-person shorter TST (b = -0.11 [-0.21, -0.01], p = .04), lower SE (b = -0.02 [-0.03, 0.00], p = .04), less SWS (b = -0.38 [-0.66, -0.10], p = .008), and less REM sleep (b = -0.32 [-0.53, -0.10], p = .004) predicted higher next-day stress. Pre-bedtime stress did not predict same-night sleep. No significant results emerged at the between-person level.

Conclusions: These findings demonstrate that poor or short sleep, measured by EEG, is predictive of higher next-day stress. Results for sleep architecture support the role of SWS and REM sleep in regulating the perception of stress. Given that only within-person effects were significant, these findings highlight the importance of examining night-to-night fluctuations in sleep affecting next-day stress and its impact on daytime functioning.

Keywords: Daily; EEG; EMA; International students; Sleep; Stress.

Graphical Abstract

Fig. 1.

Summary of the Stress and Health Study recruitment process. The recruitment period was between February 2019 and June 2020.

Fig. 2.

Diagram of the Stress and Health Study procedures. The top of the diagram shows the initial, baseline online survey phase after which eligible participants were invited to 15-day daily phase of the study, which always commenced on a Monday and completed on a Tuesday 2 weeks later. Daily measures were completed via the MetricWire mobile phone application and night-time EEG sleep via the Z-Machine Insight+. During the daily phase, participants completed five surveys per day via MetricWire (middle of diagram) assessing self-reported sleep via sleep diary and daytime and evening stress. Participants were provided training on how to complete the surveys and wear the Z-Machine Insight+ during the 1-hour, in-person orientation. Participants were instructed to clean their skin (with the provided alcohol wipes) and attach the disposable sensors (i.e., one-time use) approximately 30-minutes before their bedtime. Participants were instructed to only attach the cables to the EEG device when attempting to sleep. In addition to hands-on demonstration, participants also were provided with an instruction manual for reference at home. Surveys were available during a broad window with the median number of seconds to complete each survey shown in the figure as well as the median timing in minutes (min) of each survey, relative to wake, open of the available period, or bedtime. No. of Obs. is the number of observations available for each survey.