Reduced heart rate variability and increased saliva cortisol in patients with TMD

Temporomandibular disorders (TMD) are the most common source of non-dental pain. The pathogenesis of TMD is multifactorial, involving biological, psychological and behavioral factors. Those factors are involved with alterations of the autonomic nervous system (ANS) and stressful conditions. Heart rate variability (HRV) has been used as a marker of ANS function. Increased cortisol level (a stress indicator), has been found in chronic pain. Therefore, the present study aimed to compare pain intensity, HRV, psychological factors, and salivary cortisol level between TMD patients and a control group. Twenty-one TMD patients and twenty-three healthy control subjects participated in the study. All participants underwent 24-h-Holter monitoring to record HRV. Morning unstimulated saliva samples were collected from each participant for cortisol analysis. The pain intensity was assessed using a visual analog scale. The participants were evaluated for anxiety and depression via the Hospital Anxiety and Depression Scales. We found that pain intensity and psychological distress in the TMD group were significantly greater than those of the control (p < 0.01). Pain intensity showed a positive correlation with psychological distress (p < 0.01). HRV parameters in the TMD group were significantly lower than those in the control, suggesting reduced HRV in TMD patients. Pain intensity was negatively associated with HRV. Salivary cortisol level of the TMD group was greater than that of control. Our findings indicate that reduced HRV with higher psychological distress and increased salivary cortisol levels were observed in the TMD group. Therefore, TMD patients may benefit from interventions that can restore ANS function and stress balance.