The effect of a self-help book for shift work disorder - a randomized controlled trial.

INTRODUCTION: This randomized controlled trial (NCT05633498) compared the effects of a self-help book for coping with shift work (intervention) with an active control condition consisting of sleep hygiene advice among healthcare workers. METHODS: Data were collected from 199 healthcare workers (100 in the intervention group and 99 in the control group) with shift work disorder (SWD) (86.9% females, mean age 39 years). Participants completed questionnaires on SWD and sleep, a knowledge test about shift work, turnover intention, self-reported sickness absence and work-related fatigue at baseline and 6 months follow-up. Linear mixed-effects models were used for continuous outcomes, mixed-effects logistic regression for binary outcomes, and mixed-effects negative-binomial regression for count outcomes. RESULTS: In total, 136 participants (68.3%) completed follow-up. SWD prevalence decreased to 83.1% in the control group and 79.0% in the intervention group (no significant interaction effect). Knowledge scores increased in the intervention (7.5 to 8.4), but not in control (7.2 to 7.1). No significant interaction effects were found for turnover intention (estimate = -0.64, SE = 0.42, p = 0.13), sickness absence (IRR = 0.85; 95% CI: 0.44-1.62; p = 0.62), or sleep related sickness absence (IRR = 0.59; 95% CI: 0.24-1.43; p = 0.24). For three of five fatigue dimensions; lack of energy (p = 0.014), lack of motivation (p = 0.018), and sleepiness (p = 0.021), the time × group interactions were statistically significant favoring the intervention. CONCLUSION: Compared with sleep hygiene advice, the self-help book was associated with greater improvements in knowledge about shift work and three dimensions of self-reported fatigue. However, it did not reduce SWD or insomnia, and the findings do not support the book as an effective treatment for SWD. CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/study/NCT05633498?cond=Shift%20Work%20Disorder&viewType=Card&rank=6, identifier NCT05633498.