Elsevier

Biological Psychology

Volume 76, Issue 3, October 2007, Pages 170-173
Biological Psychology

Impaired sleep after bedtime stress and worries

https://doi.org/10.1016/j.biopsycho.2007.07.010Get rights and content

Abstract

Stress is assumed to impair sleep, but there is very little empirical evidence for this using sleep recordings. Here, we recorded sleep (at home) in 33 normal participants on three nights, which followed days with low, high and intermediate stress. The participants made daily ratings of the level of stress/worries at bedtime and also two-hourly ratings of stress. Only those 16 individuals who differed in stress/worries between two nights were analysed. There was a significantly lower sleep efficiency (81.0% versus 85.2%) a higher percent Wake (22.6% versus 15.6%) and a longer latency to Stage 3 (33.9 versus 18.3 min) during the nights with a higher stress/worry bedtime rating. None of the other sleep variables were affected. Also mean daytime stress ratings were significantly higher on the day preceding and following the high stress/worries sleep. It was concluded that moderate increases in stress/worries at bedtime are associated with moderately impaired sleep.

Introduction

The diagnostic classification of sleep disorders ICSD (2) has stress as the main aetiological factor of primary (psychophysiological) insomnia (AASM, 2001) and it has been demonstrated that a precipitating factor of insomnia may be an increased incidence of life events (Healey et al., 1981) .The relation of sleep to stress is also obvious from cross-sectional questionnaire studies (Ancoli-Israel and Roth, 1999, Urponen et al., 1988). Work demands per se are associated with reports of disturbed sleep (Åkerstedt et al., 2002). In the latter study, it was also found that it was the high effort component of work demands that was most closely related to disturbed sleep—not merely “having a lot to do”. It was also found that not being able to stop thinking about work in the evening was a better predictor of disturbed sleep than work demands. Similarly, rumination at bedtime is related to reports of disturbed sleep (Harvey et al., 2005)

With regard to sleep physiology (polysomnography (PSG) – electroencephalography, electro-oculography, and electromyography) and stress, the state of knowledge is less clear. Some early studies involving unpleasant films before sleep do not show much effect other than intensified REM sleep (Baekeland et al., 1968, Cohen, 1975, Goodenough et al., 1975). Among studies of real-life stress, the effect of losing a life partner involved increased REM intensity (Reynolds et al., 1993), an impending exam resulted in reduced total sleep time (TST) (Holdstock and Verschoor, 1974, Lester et al., 1967) (and sleep Stages 3 + 4 (slow wave sleep – SWS) in the latter study) or increased REM (Becker-Carus and Heyden, 1979), and an impending coronary by-pass operation led to increased sleep fragmentation (Edéll-Gustafsson, 2002). The latter was correlated with intrusive thoughts. Beaumaster et al. (1978), on the other hand, found no effect on PSG variables in inexperienced sky divers during the night before the first jump.

Several studies have used the first night in the sleep laboratory as a stressor and Drake et al., for example, have shown that those who report higher habitual sleep vulnerability to stress also show longer sleep latency and lower sleep efficiency on the first night in the laboratory (Drake et al., 2004). However, this study was cross-sectional. Hall et al. have demonstrated in a cross-sectional study that intrusive thoughts at bedtime are related to increased alpha and beta power in the sleep EEG (Hall et al., 2000). Similarly, increased cognitive arousal at bedtime is related to increased sleep latency (Haynes et al., 1981, Tang and Harvey, 2004), but the former did not report on other sleep parameters and the latter only included actigraphy.

Only three studies seem to have looked at some kind of work stress. Thus, Stage 2 increased and SWS decreased in merchant marine officers on call (on nights without calls to duty) compared to being off duty (Torsvall and Åkerstedt, 1988). Presumably, some kind of apprehension of being awakened was involved, but this was not formally investigated. In fact, none of the previously cited studies seem to have used the individual's perception of stress as a guide to whether the night supposedly representing stress exposure was actually perceived as such. In another study, early morning flights shortened sleep duration and reduced SWS. The latter was related to self-rated apprehension of the early awakening (measured at bedtime) (Kecklund and Åkerstedt, 2004, Kecklund et al., 1997). This may be related to the effect of rumination discussed above.

The above review suggests a need for more knowledge about the relation between normal day-to-day stress and physiological sleep parameters. This should be accomplished through a longitudinal approach to avoid the high risk of confounding in cross-sectional studies. However, an experiment which actually manipulates everyday stress might be difficult to carry out with full ecological validity. One could instead conceive of using before/after designs where knowledge is available on a future stressful situation like, for example, the pre-surgery sleep study cited above. Individuals may differ, however, in their response to stressors. Some of the absence of clear results in previous work could be due to the stressor being perceived as such only by some of the participants. Therefore, it might be more fruitful to record several sleep episodes across a few weeks and select those sleep episodes that are preceded by a perception of stress/worries at bedtime and compare this episode with a sleep episode with low levels of stress/worries. The combination of ratings of stress and worries at bedtime is based on the observations of rumination or preoccupation with work as a cause of disturbed sleep as discussed above. Furthermore, in contrast to previous studies of stress, sleep recordings should probably be carried out in the participant's home, rather than in a sleep laboratory, since the latter might influence the natural response to the stress exposure. The present study was designed to provide data on the relation between self-reported stress/worries at bedtime and sleep physiology.

Section snippets

Methods

A total of 52 individuals were approached, of whom 46 accepted and 33 went through the entire study. The loss of the 13 participants was mainly due to illness, travel, job schedules, etc. interfering with participation. All were recruited through advertisements and contacts. All participants were apparently healthy and, specifically, did not complain of insomnia. The mean age was 44 years (range 28–69), 75% worked (the remainder were students or retired), 87% were married and 28% had small

Results

Three participants had to be removed because of incomplete data. Of the 90 resulting sleep episodes 61% had a rating of 5 (no stress/worries), 30% had a rating of 4 and 5% had a rating of 3. Thus, the number of sleep episodes with any indication of stress/worries was rather low. A total of 17 participants showed a difference between at least 2 sleep episodes ≥1, but the mean difference was moderate (see Table 1). The high stress/worries night appeared as night 1 for 5 participants, night 2 for

Discussion

Bedtime stress/worries were related to increased SWS latency, decreased sleep efficiency and an increased WASO. Obviously, the latter forms part of the former and both are at the top of the list of indicators of disturbed sleep (Littner et al., 2003). SWS is not an established clinical indicator of disturbed sleep but impairment is frequently seen in insomnia (Pigeon and Perlis, 2006). The previously discussed reduction of TST on the night before an exam (Holdstock and Verschoor, 1974, Lester

Acknowledgement

This paper was supported by the Swedish Council for Research in Working Life and Social Science, the Swedish Council of Research Councils, and the Alecta AB insurance company.

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