Experienced Demand Does Not Affect Subsequent Sleep and the Cortisol Awakening Response

Abstract

Purpose

Stress is associated with subjective and objective sleep disturbances; however, it is not known whether stress disrupts sleep and relevant physiological markers of stress immediately after it is experienced. The present study examined whether demand, in the form of cognitive tasks, disrupted sleep and the cortisol awakening response (CAR), depending on whether it was experienced or just anticipated.

Participants and Methods

Subjective and objective sleep was measured in 22 healthy adults on three nights (Nights 0–2) in a sleep laboratory using sleep diaries and polysomnography. Saliva samples were obtained at awakening, +15, +30, +45 and +60 minutes on each subsequent day (Day 1–3) and CAR measurement indices were derived: awakening cortisol levels, the mean increase in cortisol levels (MnInc) and total cortisol secretion (AUC_G). On Night 1, participants were informed that they were required to complete a series of demanding cognitive tasks within the sleep laboratory during the following day. Participants completed the tasks as expected or unexpectedly performed sedentary activities.

Results

Compared to the no-demand group, the demand group displayed significantly higher levels of state anxiety immediately completing the first task. There were no subsequent differences between the demand and no-demand groups in Night 2 subjective sleep continuity, objective sleep continuity or architecture, or on any Day 3 CAR measure.

Conclusion

These results indicate that sleep and the CAR are not differentially affected depending on whether or not an anticipated stressor is then experienced. This provides further evidence to indicate that the CAR is a marker of anticipation and not recovery. In order to disrupt sleep, a stressor may need to be personally relevant or of a prolonged duration or intensity.

Keywords:

• stress
• cortisol
• polysomnography
• sleep
• anticipation

Abbreviations

ANOVA, analysis of variance; AUC_G, area under the curve with respect to ground; CAR, cortisol awakening response; EEG, electroencephalography; EMG, electromyography; MnInc, mean increase; N1, non-rapid eye movement stage 1; N2, non-rapid eye movement stage 2; N3, non- rapid eye movement stage 3; NWAK, number of awakenings; PSG, polysomnography; REM, rapid eye movement; SE, sleep efficiency; SOL, sleep onset latency; TIB, time in bed; TST, total sleep time; WASO, wake after sleep onset.

Ethics Approval and Informed Consent

This study was ethically approved by the Northumbria University Faculty of Health and Life Sciences ethics committee. All participants provided written informed consent.

Acknowledgments

We would like to thank all study participants. We thank Dr. Zoe Gotts, Dr. Rachel Sharman, Dr. Umair Akram for their assistance with data collection and Anthea Wilde for conducting the saliva analyses. This study was financially supported by Northumbria University.

Author Contributions

GE led data analysis and wrote and drafted the manuscript. All authors (GE, MW, TP, NB and JE) contributed to the study design, data analysis and subsequent drafts of the manuscript. All authors contributed to data analysis, drafting and revising the article, gave final approval of the version to be published, and agree to be accountable for all aspects of the work.

Disclosure

The authors declare that they have no financial or non-financial competing interests.

Additional information

Funding

This study was financially supported by Northumbria University.