Objective: To examine the prospective effects of psychosocial job characteristics evaluated with the Demand-Control-Support (DCS) and Effort-Reward Imbalance (ERI) models on insomnia.
Methods: A prospective cohort study with a two-year observation was performed. The subjects were 1022 middle-aged (>or= 39 years) Japanese workers. The following associations were analyzed: high job strain, low social support, effort-reward imbalance, and overcommitment to work at the baseline with self-reported persistence and future onset of insomnia.
Results: Among those who were insomniacs at the baseline (N=292), low social support [adjusted odds ratio (95% CI): 2.00 (1.18, 3.40)] and effort-reward imbalance [2.40 (1.13, 5.10)] at the baseline had a significant relationship to insomnia at the follow-up. Among those who were not insomniacs at the baseline (N=730), overcommitment to work [1.75 (1.16, 2.66)] and high job strain [1.72 (1.06, 2.79)] at the baseline were associated with insomnia at follow-up.
Conclusions: Prospective effects of psychosocial job characteristics on insomnia differed between its persistence and future onset. Proportionate reward for work effort and sufficient support at work assist recovery from insomnia, while overcommitment to work and high job strain cause future onset of insomnia.