The intra-day link between sleep disturbance and pain severity among individuals with temporomandibular joint disorder: Pain expectancy as a potential mechanism

Most individuals with temporomandibular joint disorder (TMD) report experiencing sleep disturbance, which can maintain and exacerbate pain severity. However, the factors underlying the sleep-pain link, especially at the within-person level, have not been fully elucidated. Previous studies suggest that sleep disruption can induce biased attentional and interpretative processes, which can potentially elevate pain expectancy—a potent psychological factor that shapes pain experience. We examined whether morning pain expectancy serves as a mediator in the association between previous night sleep disturbance and pain severity the following evening. The sample included 170 women (mean age=36.3 [SD=11.4]) with co-morbid TMD and insomnia. Sleep was assessed for 14 days using actigraphy. Sleep parameters, including total sleep time (TST), wake after sleep onset (WASO), and sleep onset latency (SOL), were extracted from the data. Subjective reports of previous night sleep and current pain expectancy were measured upon participant's waking, and subsequent pain-related reports were collected at end-of-day during the same 14-day period. Multilevel structural equation modeling was employed to analyze the nested data. The Rmediation software was used to test the significance of the mediated effects. Shorter previous night TST predicted higher pain expectancy (B=-.001, p=.021), such that shorter TST was associated with higher pain expectancy. TST (B=-.002, p=.007) and WASO (B=.002, p=.047) significantly predicted morning pain. Morning pain expectancy (B=.140, p