Predictors of Long-Term Temporomandibular Disorder Pain Intensity: An 8-Year Cohort Study

Aims: To investigate, in individuals with pain-related temporomandibular disorder (TMD), the association of long-term pain intensity with baseline health-related quality of life (HRQoL) and jaw functional limitation. Methods: Of 513 cases with baseline pain-related TMD (masticatory muscle and/or temporomandibular joint [TMJ] pain), 273 were reevaluated after 8 years, and 258 of them had complete baseline data for Jaw Functional Limitation Scale (JFLS) scores and HRQoL measured by the Physical Component Summary (PCS) and Mental Component Summary (MCS) scores of the 12-item Short Form Health Survey and follow-up data for Characteristic Pain Intensity (CPI) from the Graded Chronic Pain Scale. Secondary analyses of existing data quantified the effects of primary (PCS, MCS) and secondary (JFLS) predictors on follow-up CPI by using multivariable linear regression. Sensitivity analyses considered differences between the included participants (n = 258) and those who were not included (n = 255) by using inverse probability weighting. Interactions of baseline predictors with age, sex, and baseline CPI were evaluated using multivariable linear regression. Results: The score for baseline PCS, but not MCS or JFLS, was associated with follow-up CPI (P = .012). One standard deviation (SD = 9.0)-higher baseline PCS score predicted an overall 3.2-point-lower follow-up CPI (95% confidence interval -5.8 to -0.7) after adjusting for age, sex, MCS, JFLS, and baseline CPI scores. However, the effect of PCS score was not uniform: the association between PCS and follow-up CPI scores was statistically significant for participants with baseline CPI ≥ 51.3/100 and clinically significant for participants with baseline CPI ≥ 68.7/100. Adjustment for TMD treatments and sensitivity analyses had negligible effect. Conclusion: In participants with moderate to severe baseline TMD pain intensity, higher baseline physical HRQoL predicted lower TMD pain intensity at 8 years follow-up. PCS score could contribute to a multifactorial long-term TMD pain prediction model. Keywords: chronic pain, epidemiology, facial pain, quality of life, temporomandibular disorders