Impaired sleep after bedtime stress and worries
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.
References (34)
- et al.
Sleep disturbances, work stress and work hours. A cross-sectional study
Journal of Psychosomatic Research
(2002) - et al.
Cognitive approaches to insomnia
Clinical Psychology Review
(2005) - et al.
Apprehension of the subsequent working day is associated with a low amount of slow wave sleep
Biological Psychology
(2004) - et al.
Quantitative criteria for insomnia
Behavioral Research & Therapy
(2003) - et al.
Sleep homeostasis in primary insomnia
Sleep Medicine Reviews
(2006) - et al.
Sleep after spousal bereavement: A study of recovery from stress
Biological Psychiatry
(1993) - et al.
Self-evaluations of factors promoting and disturbing sleep: An epidemiological survey in Finland
Social Science & Medicine
(1988) ICSD – International Classification of Sleep Disorders, Revised: Diagnostic and Coding Manual
(2001)- et al.
The first night effect: an EEG study of sleep
Psychophysiology
(1966) - et al.
Characteristics of insomnia in the United States: results of the 1991 National Sleep Foundation survey. I.
Sleep
(1999)
EEG arousals: scoring rules and examples
Sleep
Effects of a stressful presleep experience on electroencephalograph-recorded sleep
Psychophysiology
The sleep of skydivers: a study of stress
Psychophysiology
Stress-Wirkungen in Labor- und Realsituationen in Abhängigkeit von REM-Schlaf und psychophysiologischer Aktivation
Zeitschrift für Experimentelle und Angewandte Psychologie
Eye movements during REM sleep: the influence of personality and presleep conditions
Journal of Personality and Social Psychology
Different levels of work-related stress and the effects on sleep, fatigue and cortisol
Scandinavian Journal of Work, Environment and Health
Vulnerability to stress-related sleep disturbance and hyperarousal
Sleep
Cited by (178)
Too stressed to sleep? Downsizing, job insecurity and sleep behavior
2023, Economics and Human BiologyInsomnia risk factors
2023, Encyclopedia of Sleep and Circadian Rhythms: Volume 1-6, Second Edition