Browsing by Author "Nahi, Johanna"

Objectives: Sleep is sensitive to mental stress. Mental stress can be triggered by everyday psychosocially stressful life events evoking feelings of fear of social evaluation, social exclusion or pressure of attaining desired goals. Deterioration of subsequent sleep is in turn widely associated with different mental health outcomes. Here we examine, whether psychosocial stress experienced before night sleep affects non-rapid eye movement (NREM) sleep architecture and sleep spindles. Furthermore, we intend to elucidate whether the effects of stress are different between two halves of the night. To our knowledge this is the first study integrating these themes and covering the entire night EEG measurement. Methods: Subjects were 20- to 34-year-old healthy adults (n=34) distributed into two experimental groups, completing different virtual reality scenarios. Subjects of stress condition performed a public speaking task in front of an attentive virtual audience whereas the subjects of control condition listened a neutral presentation in otherwise identical except empty virtual seminar room. Following both virtual reality scenarios participants’ sleep parameter data were gathered with electroencephalography (EEG) during the following night in the sleep laboratory. Results and Conclusions: We found that participants in stress condition displayed significantly lower N2 proportion during the first half of the night in contrast to control condition, accompanying slight reduction in N3 and REM sleep. Psychosocial stress had no significant effect on the entire night sleep spindle parameters, compared to non-stressful condition. However, a significant interaction between group and time on central spindle density was found, as a significant increase of central spindle density in the stress group from first to second half of sleep. Thus, we conclude that pre-sleep psychosocially stressful experience is associated with decreased N2 proportion during the first half of the sleep and increased central spindle density from the first to second half of the sleep, and the pattern is significantly different compared to sleep after neutral experience. These findings might indicate potential sleep homeostatic mechanism, whereby the stress related reduction of N2 sleep observed earlier in the night may be compensated for by a denser appearance of spindles later in the night, thus promoting sleep continuity and compensating for effects which occurred closer to the stressor.