1 Section of Social Medicine, Department of Public Health, Faculty of Health and Medical Sciences, Københavns Universitet2 Finnish Institute of Occupational Health, Helsinki, Finland ; Department of Psychology, University of Turku, Turku, Finland.3 Institute of Health Sciences, University of Oulu, Oulu, Finland.4 Division of Biological Psychology and Treatment Research, Stress Research Institute, Stockholm University, Stockholm, Sweden ; Department of Psychology, Swansea University, Swansea, UK.5 Finnish Institute of Occupational Health, Helsinki, Finland.6 Finnish Institute of Occupational Health, Helsinki, Finland ; Department of Epidemiology and Public Health, University College London Medical School, London, UK.7 Finnish Institute of Occupational Health, Helsinki, Finland ; Department of Public Health, University of Turku and Turku University Hospital, Turku, Finland.8 Section of Social Medicine, Department of Public Health, Faculty of Health and Medical Sciences, Københavns Universitet
Prospective Cohort Study of Finnish Public Sector Employees
OBJECTIVES: Employee control over work times has been associated with favorable psychosocial and health-related outcomes, but the evidence regarding sleep quality remains inconclusive. We examined cross-sectional and prospective associations between work time control and sleep disturbances in a large working population, taking into account total hours worked. METHODS: The data were from a full-panel longitudinal cohort study of Finnish public sector employees who responded to questions on work time control and sleep disturbances in years 2000-2001, 2004-2005, 2008-2009, and 2012. The analysis of cross-sectional associations was based on 129,286 person measurements from 68,089 participants (77% women) aged 17-73 years (mean 43.1). Data from 16,503 participants were used in the longitudinal analysis. Log-binomial regression analysis with the generalized estimating equations method was used. RESULTS: Consistently in both cross-sectional and longitudinal models, less control over work time was associated with greater sleep disturbances in the total population and among those working normal 40-hour weeks. Among participants working more than 40 hours a week, work time that was both very high (cross-sectional prevalence ratio compared to intermediate work time control [PR] 1.32, 95% confidence interval [CI] 1.05-1.65) and very low (PR 1.23, 95% CI 1.08-1.39) was associated with sleep disturbances, after adjustment for potential confounding factors. CONCLUSIONS: These data suggest that having few opportunities to influence the duration and positioning of work time may increase the risk of sleep disturbances among employees. For persons working long hours, very high levels of control over working times were also associated with increased risk of sleep disturbances. CITATION: Salo P, Ala-Mursula L, Rod NH, Tucker P, Pentti J, Kivimäki M, Vahtera J. Work time control and sleep disturbances: prospective cohort study of Finnish public sector employees. SLEEP 2014;37(7):1217-1225.