Relationships of occupational stress to insomnia and short sleep in Japanese workers.

Study Objective: The aims of this study were to (a) examine the association between occupational stress and insomnia and short sleep in Japanese workers and (b) demonstrate the difference between 2 occupational stress models-Effort Reward Imbalance and the Demand Control Model. Design: All data were obtained via self-administrated questionnaires and annual health checkups. Insomnia was evaluated by the Athens Insomnia Scale, and short sleep was defined as less than 6 hours sleep per day. Setting: Employees at local governments and a transit company who had annual health checkups during the period from April 2003 to March 2004. Participants: After excluding participants without complete data, data from 6,997 men and 1,773 women were analyzed. Intervention: N/A. Measurements and Results: In men, high occupational stresses were significantly associated with insomnia, especially a high level of Effort Reward Imbalance (defined as the presence of high effort and low reward), had a remarkably higher odds ratio. In women, high occupational stresses were significantly associated with insomnia as well. High occupational stresses were significantly associated with short sleep in men. However, in women, only Effort Reward Imbalance showed a significant association with short sleep. Conclusions: This study suggested that occupational stress is a possible risk factor for insomnia and short sleep.