Effects of sleep and circadian rest–activity rhythms on daily pain severity in women with temporomandibular disorders

Abstract Although a robust connection between sleep and pain is established, the extent to which circadian rest–activity rhythms contribute toward unique variations in pain, beyond what is elucidated by sleep, remains uncertain. Furthermore, it is largely unknown whether sleep and circadian rest–activity rhythms have interactive effects on daily pain severity. Using wrist actigraphy and daily pain diaries, data from 140 women with temporomandibular disorders and insomnia symptoms were analyzed over a 14-day period. Sleep duration and continuity were quantified by using total sleep time (TST) and wake after sleep onset (WASO), and circadian rest–activity rhythms were characterized with the Relative Amplitude (indicating strength/robustness of rest–activity rhythm) and Intradaily Variability metrics (representing rhythm fragmentation). Linear mixed-effects modeling revealed that both TST ( b = −0.11, P = 0.006) and WASO ( b = 0.18, P = 0.006) from the previous night, along with Relative Amplitude ( b = −2.56, P = 0.001) from the past 24 hours, predicted next-day pain severity. Among the 4 interaction effects tested, both Intradaily Variability ( b = 1.52, P = 0.034) and Relative Amplitude ( b = −1.52, P = 0.003) moderated the relationship between WASO and next-day pain severity; on days characterized by less robustness (lower Relative Amplitude) or greater fragmentation (higher Intradaily Variability) in the circadian rest–activity rhythm, the positive association between previous night WASO and next-day pain severity intensified. These findings highlight the complex interplay among sleep, circadian rest–activity rhythms, and pain. While preliminary, our findings indicate that interventions aimed at improving both sleep and restoring circadian rhythms may provide enhanced benefits for managing chronic pain.