This study examined how the cessation of work at retirement affects daily measures of actigraphy-measured and self-rated sleep quality. Time in bed or asleep and stress at bedtime were examined as potential mechanisms. In total 117 employed participants who were aged 60-72 years and planned to retire soon were recruited to the Swedish Retirement Study. Sleep quality was measured in a baseline week using accelerometers, diaries, and questionnaires. Subjective sleep measures were sleep quality, restless sleep, restorative sleep, getting enough sleep, estimated wake after sleep onset, difficulties falling asleep, too early final awakening, and difficulties waking up. Actigraphy measures were sleep efficiency, wake after sleep onset, and average awakening length. After 1 and 2 years, the measurements were repeated for the now retired participants. Daily variations in sleep quality before and after retirement were analysed using multilevel modelling, with time in bed or asleep and stress at bedtime as potential mediators. We found that several self-reports of sleep improved (e.g., +0.2 standard deviations for sleep quality and +0.5 standard deviations for restorative sleep) while objective sleep quality remained unchanged or decreased slightly with retirement (e.g., -0.8% for sleep efficiency). Increased time in bed or asleep and stress at bedtime accounted partially for the improvements in self-rated sleep quality at retirement. In conclusion, actigraph-measured and self-reported sleep quality do not change in concert at retirement, highlighting the interest of studying both outcomes. The main effects of retirement from work concern subjective experiences of recovery more than sleep quality per se.

Work may affect sleep by reducing the time available for recovery and, via work stress, by reducing sleep quality. Further, people experiencing sleep disturbance may be less resistant to work stress. These processes may lead to the development of a vicious cycle between work and sleep, in which stress has a central role.

Knowledge of the prospective relations between work, stress and sleep is limited, particularly from studies examining relationships from sleep to work stress and large-scale studies using objective measures of sleep.

Consequently, this thesis aims to analyse the prospective relations, including directions of effects, between work-related factors, in particular work stress, and self-rated and objective measures of sleep.

The first two studies used the Swedish Longitudinal Occupational Survey of Health, with biennial self-rated measures of work-related factors (demands, control, support, stress, physical factors, scheduling) and sleep. We used structural equation models to analyse the direction of effects between work-related factors and sleep. The next two studies used the Swedish Retirement Study, a prospective study using self-reports and actigraphy, which followed people into retirement. We used multilevel modelling to analyse within-individual changes in sleep duration, timing and quality over three waves across retirement.

We observed prospective reciprocal relations between work stressors (demands, control and support), perceived stress and self-rated sleep quality. Work was associated with earlier timing of sleep and sleep deprivation of 30 minutes per night. Improvements in self-rated sleep quality after retirement were not accompanied by improvements in actigraph-measured sleep quality.

In conclusion, this thesis has demonstrated that work, stress and sleep form a vicious cycle. Interventions targeting sleep disturbance could improve people’s experience of their work environments. Likewise, interventions aiming to lower stress and increase the flexibility of work could reduce the impact of work on sleep, and thereby on health, contributing to a decent and sustainable working life.

Sammanfattning

Arbete kan påverka sömnen både genom att minska tiden för återhämtning, och genom att arbetsrelaterad stress kan ge en försämrad sömnkvalitet. Sömnstörningar kan i sig minska motståndskraften mot stress, vilket riskerar att skapa en negativ spiral mellan arbete och sömn. 

Evidensen kring hur arbete, stress och sömn påverkar varandra över tid är bristfällig. Framför allt saknas studier om hur sömn kan påverka arbete samt större studier med objektiva sömnmått.

Avhandlingens syfte är därför att studera hur arbete, stress och sömn relaterar till varandra över tid, och effekternas riktning, där sömn mäts både med objektiva och självrapporterade mått. 

I de två första studierna användes Svenska Longitudinella studien Om Sociala förhållanden, arbetsliv och Hälsa (SLOSH) med självskattade mätningar vartannat år. Genom strukturell ekvationsmodellering (SEM) analyserade vi riktning av effekter mellan arbetsrelaterade faktorer (krav, kontroll, socialt stöd, stress, fysisk arbetsmiljö och arbetstider) och sömn över två år. I de två senare studierna användes data från den svenska Pensioneringsstudien, i vilken vi följt människor i övergången från arbete till pension och mätt deras sömn, arbetsrelaterade faktorer och hälsa. För att analysera hur arbete påverkade sömnlängd och sömnkvalitet använde vi oss av flernivåmodellering där vi jämförde deltagarna med sig själva, innan och efter pensionering. 

Vi fann att krav, kontroll, socialt stöd och upplevd stress var kopplat till självskattad sömnkvalitet över tid, i båda riktningar. Arbete kunde kopplas till tidigare uppstigande och 30 minuters kortare sömn per natt. Förbättringarna vi fann i självskattad sömn efter pension följdes inte av motsvarande förbättringar i sömn mätt med aktigrafi.

Avhandlingen visar på hur arbete, stress och sömn kan skapa en negativ spiral. I ljuset av detta skulle förbättringar av arbetsmiljö och arbetstider kunna minska stress, öka sömnlängden och förbättra sömnkvaliteten hos arbetande, samtidigt som insatser mot sömnproblem skulle kunna leda till en bättre upplevelse av arbetsmiljön – och tillsammans kunna bidra till ett anständigt och hållbart arbetsliv.

Several strands of research indicate that work competes for time with sleep, but to what extent the timing and duration of sleep is affected by work is not known. Retirement offers a quasi-experimental life transition to study this in a within-individual study design. The few existing studies report that people sleep longer and later after retirement but mainly rely on self-reported data or between-individual analyses. We recruited 100 participants aged 61–72 years who were in paid work but would soon retire and measured them in a baseline week with accelerometers, diaries and questionnaires. After 1 and 2 years, the measurements were repeated for the now retired participants. Changes in sleep duration, timing, efficiency, chronotype and social jetlag were analysed using multilevel modelling. Gender, chronotype at baseline and partner's working status were analysed as potential effect modifiers. Sleep duration increased by 21 min, whereas sleep efficiency remained similar. Time of sleep onset and final awakening were postponed by 26 and 52 min, respectively, pushing midsleep forward from 03:17 to 03:37 hours. Changes in duration and timing of sleep were driven by weekday sleep, whereas weekend sleep stayed about the same. Social jetlag decreased but still occurred after retirement. Changes at retirement in sleep duration and timing were smaller for participants with a later chronotype and who had full-time working partners. These findings indicate that paid work generates sleep loss and hinders people from sleeping in line with their biological time.

Work stress and poor sleep are closely related in cross-sectional data, but evidence from prospective data is limited. We analysed how perceived stress and work stressors (work demands, decision authority and workplace social support) are related to key dimensions of insomnia over time, using structural equation modelling. Biennial measurements from a large sample of the working population in Sweden enabled us to analyse both the relationship from stress to sleep as well as that from sleep to stress. Overall, we found reciprocal relations between insomnia and all four stress measures. However, looking at the relation between each dimension of insomnia and each stress measure, there were some differences in direction of effects. In the direction from stress to sleep, all work stressors as well as perceived stress predicted both difficulties initiating sleep and difficulties maintaining sleep. The same was found for non-restorative sleep, with the exception for decision authority. In the opposite direction, difficulties maintaining sleep predicted increased levels of work demands and perceived stress. Difficulties initiating sleep stood out among the insomnia symptoms as not predicting any of the stress measures, while non-restorative sleep was the only symptom predicting all stress measures. The results advance the understanding of the stress-sleep relationship and indicate a potential vicious circle between insomnia and perceived stress as well as work stressors, suggesting that the workplace could be an arena for interventions to alleviate insomnia.

Purpose The aim of this longitudinal three-wave study was to examine (i) reciprocal associations among job demands, work-related perseverative cognition (PC), and sleep quality; (ii) PC as a mediator in-between job demands and sleep quality; and (iii) continuous high job demands in relation to sleep quality and work-related PC over time.

Method A representative sample of the Swedish working population was approached in 2010, 2012, and 2014, and 2316 respondents were included in this longitudinal full-panel survey study. Structural equation modelling was performed to analyse the temporal relations between job demands, work-related PC, and sleep quality. Additionally, a subsample (N = 1149) consisting of individuals who reported the same level of exposure to job demands during all three waves (i.e. stable high, stable moderate, or stable low job demands) was examined in relation to PC and sleep quality over time.

Results Analyses showed that job demands, PC, and poor sleep quality were positively and reciprocally related. Work-related PC mediated the normal and reversed, direct across-wave relations between job demands and sleep quality. Individuals with continuous high job demands reported significantly lower sleep quality and higher work-related PC, compared to individuals with continuous moderate/low job demands.

Conclusion This study substantiated reciprocal relations between job demands, work-related PC, and sleep quality and supported work-related PC as an underlying mechanism of the reciprocal job demands-sleep relationship. Moreover, this study showed that chronically high job demands are a risk factor for low sleep quality.

Daytime workers tend to have shorter sleep duration and earlier sleep onset during work days than on days off. Large individual differences in sleep onset and sleep duration may be observed on work days, but work usually synchronizes sleep offset to a similar time. The present study describes individual differences in sleep behaviour of 48 daytime workers (25 men, aged 20-58 years) from an iron ore mine in Northern Sweden. The aim of the study was to determine whether differences in sleep patterns during work days were associated with the outcomes of sleepiness and sleep complaints. Cluster analysis was used to group workers into two categories of sleep onset and sleep duration. The "Late Sleep Onset" cluster comprised workers who slept 1.30 h later than the "Early Sleep Onset" cluster (p < 0.0001 for all weekdays). The "Long Sleep Duration" cluster slept 1.10 h longer than the "Short Sleep Duration" cluster (p < 0.0002 for work nights). The "Late Sleep Onset" cluster reported less refreshing sleep (p < 0.01) and had lower sufficient sleep scores (p < 0.01) than the "Early Sleep Onset" cluster. The "Short Sleep Duration" cluster also reported lower scores for sufficient sleep (p < 0.04) than the "Long Sleep Duration" cluster. For combined characteristics (phase and duration), workers with a late phase and short sleep duration reported greater sleep debt and sleepiness than workers with an early phase and short sleep duration (p < 0.02). Work schedule and commuting time modulate both sleep phase and sleep duration independently. Workers, classified as having an intermediate sleep phase preference, can organize their sleep time in order to minimize sleep debt and sleepiness symptoms. Individual differences in sleep phase and duration should be considered when promoting well-being at work even among groups with similar sleep needs. In order to minimize sleep debt and sleepiness symptoms, successful sleep behaviour could be promoted involving extend use of flexitime arrangement (i.e. later starting times) and reduce use of alarm clocks.

OBJECTIVES: This study aimed to investigate the relationship between individual natural light exposure, sleep need, and depression at two latitudes, one extreme with a few hours of light per day during winter, and the other with equal hours of light and darkness throughout the year.

METHODS: This cross-sectional study included a sample of Brazilian workers (Equatorial, n = 488 workers) and a Swedish sample (Arctic, n = 1,273).

RESULTS: The reported mean total natural light exposure per 4-week cycle differed significantly between the Equatorial and Arctic regions. However, shiftworkers from both sites reported similar hours of natural light exposure. Short light exposure was a predictor for insufficient sleep.

CONCLUSION: Reduced exposure to natural light appears to increase the perception of obtaining insufficient sleep. Arctic workers were more prone to develop depression than Equatorial workers.

Study Objectives: There is limited knowledge about the prospective relationship between major work characteristics (psychosocial, physical, scheduling) and disturbed sleep. The current study sought to provide such knowledge. Design: Prospective cohort, with measurements on two occasions (T1 and T2) separated by two years. Setting: Naturalistic study, Sweden. Participants: There were 4,827 participants forming a representative sample of the working population. Measurements and Results: Questionnaire data on work factors obtained on two occasions were analyzed with structural equation modeling. Competing models were compared in order to investigate temporal relationships. A reciprocal model was found to fit the data best. Sleep disturbances at T2 were predicted by higher work demands at T1 and by lower perceived stress at T1. In addition, sleep disturbances at T1 predicted subsequent higher perception of stress, higher work demands, lower degree of control, and less social support at work at T2. A cross-sectional mediation analysis showed that (higher) perceived stress mediated the relationship between (higher) work demands and sleep disturbances; however, no such association was found longitudinally. Conclusions: Higher work demands predicted disturbed sleep, whereas physical work characteristics, shift work, and overtime did not. In addition, disturbed sleep predicted subsequent higher work demands, perceived stress, less social support, and lower degree of control. The results suggest that remedial interventions against sleep disturbances should focus on psychosocial factors, and that such remedial interventions may improve the psychosocial work situation in the long run.