Shift work can lead to mental health issues such as sleep disturbances and cognitive impairment. Neural activation in response to external sleep-related stimuli may vary according to shift work patterns. In this study, we investigated the differences in brain activity in response to sleep-related stimuli between shift-worker (SW) nurses and healthy controls (HCs), and we also assessed the relationships between sleep-related problems and brain activity. The hypothesis was that shift workers would exhibit altered activation in the prefrontal cortex (PFC) when processing sleep-related stimuli, reflecting attentional biases associated with sleep disturbances.Participants completed a cognitive task during functional magnetic resonance imaging that involved viewing sleep-related and neutral pictures. Subjective sleep was assessed using self-reported questionnaires and a 1-week sleep diary. Objective sleep parameters, along with the 24-h rest-activity rhythm, were evaluated via actigraphy conducted over 1 week. We analyzed group differences in the neural processing of sleep-related stimuli and conducted correlation analyses to explore the associations between brain activity and sleep parameters.This study included 44 SWs and 37 HCs. Compared to HCs, SWs demonstrated significantly lower activity in the dorsomedial prefrontal cortex (DMPFC) and lateral prefrontal cortex (LPFC) in response to sleep-related pictures than neutral pictures. DMPFC activity was significantly negatively correlated with subjective sleep problems (e.g., self-reported insomnia and fatigue), whereas LPFC activity was strongly correlated with actigraphy-measured 24-h rest-activity rhythm parameters (e.g., a robust 24-h rhythm).The decreased activation of the prefrontal cortex in response to sleep-related stimuli in SWs may reflect diminished attentional control over sleep and increased rumination on intrusive sleep-related thoughts. These findings enhance our understanding of the neurobiological mechanisms underlying sleep-related issues in SWs and may inform interventions to mitigate mental health problems in this population.
