Organizational justice and insomnia: a prospective cohort study examining insomnia onset and persistence

Insomnia is one of the most common health problems and causes a large social burden. Psychosocial work-related factors are reported to be associated with both insomnia onset and insomnia persistence. However, the association between organizational justice (OJ) and insomnia remains unclear. The objective of this study was to examine the effect of OJ on insomnia persistence, as well as insomnia onset. A prospective cohort study with a 1-year observational period was conducted. Self-reported questionnaire data from 1588 employees were analyzed. OJ was measured using the Japanese version of the OJ questionnaire, which has four components (distributive, procedural, interpersonal, and informational). Insomnia was assessed with the Athens Insomnia Scale. Logistic regression analysis was used to explore the effects of OJ on insomnia. Among non-insomniac subjects at the baseline (n = 1236), low overall OJ was a risk of insomnia onset even after adjustment for lifestyle and work-related variables (adjusted odds ratio 0.66; 95% confidence interval 0.51-0.85). The procedural, interpersonal, and informational justice components were also associated with insomnia onset. Among insomniac subjects at the baseline (n = 352), low overall OJ, as well as the procedural and interpersonal justice components, was associated with insomnia persistence. Although these associations became insignificant after adjustment, the interpersonal justice component showed a marginally significant association with insomnia persistence (p = 0.058). OJ, especially interpersonal justice, was revealed as an associated factor for both insomnia onset and persistence. These findings may provide useful information for prevention of insomnia among working population.