Naturalistic changes in insomnia symptoms and pain in temporomandibular joint disorder: a cross-lagged panel analysis

An increasing number of prospective studies suggest a bi-directional association between the pain and sleep quality. Few of these investigations have controlled for synchronous correlations, an important source of extraneous variance in lagged associations, which may have confounded conclusions of prior investigations. Despite high rates of insomnia in temporomandibular joint disorders (TMD), no studies have examined temporal associations between naturalistic fluctuations in insomnia and pain in TMD. We conducted cross-lagged panel analysis to examine reciprocal temporal associations between 1-month changes in insomnia symptom severity and self-reported pain over 3 months among 53 TMD patients. This rigorous analytic strategy represents a comprehensive method to explore possible reciprocal temporal associations between insomnia and pain that controls for both auto- and synchronous correlations. Analyses revealed that initial-month increases in insomnia were associated with next-month increases in average daily pain, but not vice versa. The direction of the effect was such that initial-month increases in insomnia symptom severity were associated with next-month increases in average daily pain. These data suggest that naturally occurring fluctuations in insomnia symptom severity are prospectively associated with fluctuations in daily pain experience for persons with TMD. Potential mechanisms by which insomnia might influence pain in TMD and therapeutic implications of these findings are discussed.