Autonomous nervous system response to laser acupuncture in painful TMD patients with altered cortisol rhythm: a preliminary randomized placebo-controlled trial

Purpose: Temporomandibular disorder (TMD) is a condition affecting the temporomandibular joint, chewing muscle, and surrounding structures, and often characterized by pain. Laser acupuncture (LA), consisting in the stimulation of traditional acupoints with low-intensity laser irradiation, has been reported as effective for treating chronic musculoskeletal disorders, including TMD. It has also been reported that LA can influence various autonomic nervous system (ANS) parameters, including heart rate variability. The aim of this preliminary study was to investigate LA effects on ANS parameters in patients affected by painful TMD. Methods: TMD patients (N = 52) (F = 42; M = 10; mean age = 33.79 ± 10.91) were enrolled in the study according to DC/TMD diagnostic criteria. Half of the patients were randomly allocated to LA group (LG) and aand the other half to the placebo-LA group (PLG). Before treatment, all patients underwent an evaluation of bioelectric impedance analysis (BIA). Before (T0) and after (T1) one session of active or placebo LA treatment (duration = 10 min), ANS parameters were measured using a non-invasive plethysmograph (PPG). The main outcome was the difference in ANS parameters before and after the active/placebo LA application. Results: No significant differences were found between LG and PLG, and within each group (T0-T1), for all ANS parameters evaluated using the PPG device. Considering age and BMI, a significant decrease in total power was observed between T0 and T1 in the PLG group (p = 0.009). Conclusion: LA application on acupuncture points was not effective in modulating ANS parameters in patients affected by painful TMD. Alteration of cortisol circadian rhythm in patients undergoing LA therapy may have affected the results obtained.