Effort-reward imbalance at work and risk of sleep disturbances. Cross-sectional and prospective results from the Danish Work Environment Cohort Study

Objectives: This study aimed to analyze if adverse psychosocial working conditions, defined by the model of effort-reward imbalance (ERI), increase the risk of sleep disturbances in the Danish workforce. Methods: Analyses were conducted both cross-sectionally and prospectively in a representative sample of Danish employees. The cross-sectional sample included 2614 participants (50% women) aged 18-59 years, of whom 263 had sleep disturbances. Of the 2351 participants initially free of sleep disturbances, 304 (12.9%) developed sleep disturbances during the 5-year follow-up. Data were analyzed with gender-stratified, multivariate logistic and linear regression analyses, adjusted for numerous covariates. Results: Cross-sectionally, a 1 S.D. increase in the ERI ratio was associated with sleep disturbances among both men [odds ratio (OR)=1.65, 95% confidence interval (Cl)=1.20-2.27] and women (OR-1.82, 95% CI=1.46-2.28). In the prospective analysis, a I S.D. increase of the ERI ratio at baseline predicted the onset of sleep disturbances among men (OR=1.39, 95% CI=1.03-1.87) but not among women (OR=0.97, 95% CI=0.76-1.24). Conclusion: Among men, ERI is a risk factor for the development of sleep disturbances in the Danish workforce. Among women, an association between ERI and sleep disturbances was restricted to the cross-sectional sample. Improving psychosocial working conditions might reduce the risk of sleep disturbances and subsequently also help to prevent clinical disorders related to sleep disturbances. (c) 2009 Elsevier Inc. All rights reserved.