Parasympathetic reactivity in fibromyalgia and temporomandibular disorder: associations with sleep problems, symptom severity, and functional impairment

Abstract

Despite evidence of autonomic disturbances in chronic multisymptom illnesses such as temporomandibular disorder (TMD) and fibromyalgia, additional work is needed to characterize the role of parasympathetic reactivity in these disorders. Given the high levels of comorbidity with psychiatric disorders characterized by stronger parasympathetic decline than controls in safe contexts (leading to higher arousal), it was hypothesized that individuals with TMD and fibromyalgia would respond similarly. In this preliminary investigation, 43 women with TMD (n = 17), TMD + fibromyalgia (n = 11), or neither (controls; n = 15) completed a baseline assessment of respiratory sinus arrhythmia (a measure of parasympathetic activity) followed by ongoing parasympathetic assessment during a questionnaire period. As predicted, patients showed greater parasympathetic decline during psychosocial assessment, suggesting an autonomic stance that supports defensive rather than engagement behaviors. Individual differences in parasympathetic reduction during the questionnaire period were related to a variety of physical and psychosocial variables. Although this study has a number of key limitations, including a convenience sampling approach and small group sizes, if replicated in larger samples, the findings would have important implications for the treatment of patients with these disorders.

Perspective: Compared to controls, individuals with TMD or TMD and fibromyalgia demonstrated greater parasympathetic decline during psychosocial assessment, and individual differences in parasympathetic decline predicted negative patient outcomes. Such parasympathetic decline may demonstrate a tendency to readily perceive danger in safe environments.

Keywords: Autonomic reactivity; chronic pain; fibromyalgia; polyvagal theory; respiratory sinus arrhythmia; temporomandibular disorder.

Figure 1

Graphs depicting mean levels of RSA and HP at the beginning and end of the assessment period by diagnostic group. Data points depicted are mean levels of RSA or HP within a given group during the first minute (“Beginning of Assessment Period) and last minute (“End of Assessment Period”) of the assessment phase of the study. In the upper panel, the observed decrease in RSA over time indicates “vagal withdrawal”, which is the term used to describe this phenomenon in the rest of this paper.

Figure 2

Graphs depicting the interaction between time and pain levels predicting RSA and HP during the assessment period. Lines represent the simple effects of time at the first minute (“Beginning of Assessment Period”) and last minute (“End of Assessment Period”) of the assessment period at both high (1 SD above the sample mean) and low (1 SD below the sample mean) levels of pain as indicated in the Brief Pain Inventory. In the upper panel, the observed decrease in RSA over time indicates “vagal withdrawal”, which is the term used to describe this phenomenon in the rest of this paper.