Sleep moderates the relationship between temporomandibular joint disorder and laboratory-induced pain

The prevalence of sleep disturbance in chronic pain exceeds 70%. Recent studies reveal a complex reciprocal relationship between pain and sleep. Pain disrupts both the continuity and depth of sleep, and in turn, disturbed sleep impairs endogenous pain modulation resulting in altered pain perception. Fragmented and shallow sleep is associated with poor sleep quality and excessive daytime sleepiness (EDS). This study examined whether subjective sleep quality and sleepiness moderate the relationship between temporomandibular joint disorder (TMD) and laboratory-induced pain. Fifty-three participants (62% TMD; 38% healthy controls) completed quantitative sensory testing (QST) procedures including a cold-pressor tolerance test, pressure pain threshold testing (masseter, thumb joint, & trapezius), and conditioned pain modulation. Subjective sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) and subjective sleepiness was measured with the Epworth Sleepiness Scale (ESS). TMD patients reported significantly lower sleep quality and greater daytime sleepiness than healthy controls. Clinical pain severity and pain catastrophizing were control variables due to the strong correlation of psychosocial factors and clinical pain with sleep and pain. The results demonstrated that TMD patients, and not healthy controls, reporting poor sleep quality and EDS also exhibited greater pain sensitivity. Moreover, TMD patients who reported high sleep quality and low levels of EDS showed decreased pain sensitivity, which suggests that deep and consolidated sleep exerts protective pain modulatory effects. These findings underscore the important role of sleep in the experience of pain. Thus, assessing sleep in chronic pain patients is important because interventions that target sleep disturbance may alleviate some of the adverse effects of persistent pain. Future studies should explore the ability of behavioral sleep interventions to attenuate laboratory-induced pain.