Low-grade inflammation as a potential mediator between depressive symptoms and temporomandibular pain: an 11-year follow-up study on Finnish adults.

Background: Low-grade inflammation and depressiveness have been associated with chronic pain conditions.
Objective: To examine whether low-grade inflammation mediates the association between depressive symptoms and temporomandibular (TM) pain in Finnish adults based on the Health 2000/2011 Surveys (BRIF8901).
Methods: The sample comprised subjects who underwent clinical TM pain examination (pain on palpation of the masticatory muscles and temporomandibular joints) in 2000 and 2011 and responded to questions on TM pain symptoms in 2011. The serum level of hs-CRP was obtained in both years, and depressiveness was assessed using the Beck Depression Inventory-21 (BDI-21) in 2000 and BDI-13 in 2011. Four subgroups were formed based on the presence of TM pain: No pain, pain in 2000-only, pain in the 2011-only, and pain in both-years. Analyses included Rao Scott's chi-square test cross-sectionally, and multinomial logistic regression longitudinally with the level of hs-CRP and BDI-21 score in 2000 as predictors. Mediation was tested using Hayes A. Processv3.5.
Results: Higher BDI-21/-13 and hs-CRP levels corresponded to higher prevalences of TM pain in both years. Longitudinally, in men, higher hs-CRP level predicted TM pain in 2000-only and TM pain in both-years. Higher BDI-21 score predicted having TM pain in 2011-only. In women, higher BDI-21 score predicted TM pain in 2000-only and having TM pain in both-years. Both BDI-21 and hs-CRP had a direct effect on TM pain outcome with no mediation detected.
Conclusion: While depressiveness may increase the risk of chronic TM pain in women, the risk in men is increased by low-grade inflammation.