Changes Of Pain Empathy In Patients With Chronic Non-Specific Low Back Pain

Background:Chronic non-specific low back pain（CNLBP）is defined as a“bio-psycho-social”disorder in which patients often have mental health problems,such as negative emotions like anxiety and depression,and cognitive dysfunction,the interaction of these factors may lead to changes in social functioning with CNLBP.This social dysfunction and long-term chronic pain can impair neural circuits involved in cognitive and emotional control,worsening the onset and progression of chronic pain,which in turn can affect the rehabilitation and treatment outcomes of the disease.Pain empathy,as an important part of psychosocial emotions,emphasizes the individual’s perception,judgment,and emotional response to others’pain,and this ability to understand and indirectly experience others’pain is crucial for relieving anxiety and stress and for establishing a good relationship between doctor with patient and social participation,as well as for personal pain perception and understanding.However,there is a lack of research on the effects of CNLBP on pain empathy.In this study,we analyzed the effect of CNLBP on pain empathy and its neurophysiological mechanism through the behavioral paradigm of pain empathy and ERP.The purpose of this research was to inform the rehabilitation treatment and assessment of emotional and cognitive disorders with CNLBP in order to promote comprehensive“bio-psycho-social”rehabilitation of CNLBP.Methods:（1）Participants:A total of 30 patients with CNLBP and 30 healthy individuals were recruited;（2）Assessment scales:The basic empathy scale,psychological and pain-related scales;（3）The paradigm of pain empathy:According to previous studies,a total of 30pictures with pain condition and 30 matching neutral pictures were taken.The intensity of others pain and self-emotion scores for the collected pictures were assessed by a web questionnaire with the aim of verifying whether the collected stimulus material could significantly induce empathy in the participants.The experimental paradigm was compiled by E-prime 3.0 program.The experiment was conducted in two conditions:an explicit task condition（participants were asked to determine quickly and accurately whether the hand of the person in each picture felt pain or no-pain and to respond by pressing a button）;and an implicit task condition（participants were asked to judge the left and right of the hand in the picture and to respond by pressing a button）,and the program automatically recorded the reaction times and accuracies.Scalp EEG signals were recorded using a Neuroscan 64-channel EEG device while the task was in progress.At the end of the explicit and implicit tasks,participants were asked to rate other’s pain intensity and self-unpleasantness.Results:（1）Stimulus materials:to verify whether the stimulus materials could generate empathy,the pain intensity of others and self-unpleasantness ratings were assessed by questionnaires.The total of 87 questionnaires were included through screening,and the results showed that for all collected stimulus materials significantly induced emotional empathy（P<0.001）and cognitive empathy（P<0.001）.（2）Behavioral results:the basic empathy scale,the CNLBP group had significantly lower emotional empathy scores than the healthy group（20.13±3.91 vs 22.76±3.61,P<0.05）,and there was no significant difference between the two groups on cognitive empathy（32.43±2.98 vs 33.03±3.45,P>0.05）,in terms of both affective disconnection and total empathy scores,the CNLBP group scored significantly lower than the healthy group（21.30±3.81 vs 24.07±3.08,P<0.05）;（73.83±7.90 vs79.83±6.52,P<0.05）.Results at reaction time revealed a significant main effect of group(F_1,58=4.354,P<0.05,η_p²=0.070),with the CNLBP group having significantly slower reaction time to painful stimuli and neutral stimuli than the healthy group.In the explicit,neutral stimuli had significantly greater reaction times than painful stimuli(F_1,58=66.591,P<0.001,η_p²=0.534).On accuracies,the main effect of stimulus(F_1,58=77.258,P<0.001,η_p²=0.617)was significant,and both groups were significantly less correct than the neutral stimulus（0.84±0.08 vs 0.92±0.07,P<0.001）.The others’pain intensity in stimulus(F_1,58=500.322,P<0.001,η_p²=0.896)main effect was significant,with significantly higher pain stimulus others pain stimulus scores compared to neutral stimuli（4.43±1.47 vs 0.20±0.47,P<0.001）.The interaction effect between group and stimulus(F_1,58=10.594,P<0.05,η_p²=0.154)was significant.Post hoc test analysis,for pain stimuli,the CNLBP group had significantly lower others pain scores than the healthy group（3.86±1.36 vs 5.00±1.38,P<0.05）.For neutral stimuli,there was no significant difference between the two groups（0.15±0.23 vs0.24±0.616,P>0.05）.The main effect of self-unpleasantness scores in stimuli(F_1,58=492.411,P<0.001,η_p²=0.895)was significant,and self-unpleasantness scores were significantly higher for pain stimuli than neutral stimuli.Between-group(F_1,58=4.506,P=0.038,η_p²=0.072)main effects differed significantly,with significantly higher self-unpleasantness scores in healthy group than in CNLBP group.Group and stimulus(F_1,58=4.566,P=0.037,η_p²=0.073)interactions were significant.Post hoc test analysis,for painful stimuli,self-unpleasantness scores were significantly lower in CNLBP group than in healthy group（4.29±0.29 vs 5.21±0.29,P<0.05）.For neutral stimuli,there was no significant difference between the two groups（0.29±0.07 vs 0.24±0.07,P>0.05）.（3）ERP results:early component N1 was not significant for group main effect(F_1,58=0.336,P>0.05,η_p²=0.006)and stimulus main effect was not significant(F_1,58=0.070,P>0.05,η_p²=0.001).Early component N2 found a significant stimulus and group interaction effect(F_1,58=5.219,P<0.05,η_p²=0.083),Post hoc test analysis,for the healthy group,the difference between pain stimulus and neutral stimulus N2was not significant(F_1,58=0.996,P>0.05,η_p²=0.017),the CNLBP group differed significantly for painful and neutral stimuli N2(F_1,58=4.986,P<0.05,η_p²=0.079),and for the CNLBP group,painful stimuli evoked significantly lower N2 than neutral stimuli（-9.05±0.97μv vs-10.38±0.90μv）.For the late component P3,significant stimulus main effects(F_1,58=6.650,P<0.05,η_p²=0.103)and task main effects(F_1,58=31.914,P<0.001,η_p²=0.355)were found,in addition to significant stimulus and task interaction effects(F_1,58=7.857,P<0.05,η_p²=0.119).Post hoc test analysis,in explicit task,pain stimuli and neutral stimuli evoked significant differences in P3components(F_1,58=13.917,P<0.001,η_p²=0.194),with pain stimuli evoking significantly larger P3 than neutral stimuli（11.23±0.57μv vs 9.86±0.58μv,P<0.001）,and in implicit task,the difference in the P3 evoked by painful stimuli was not significant(F_1,58=0.026,P>0.05,η_p²=0.001).For the late component LPP,a significant stimulus main effect was found(F_1,58=28.988,P<0.001,η_p²=0.333).Task main effects were significant(F_1,58=31.175,P<0.001,η_p²=0.350),stimulus and task interaction effects were significant(F_1,58=22.950,P<0.001,η_p²=0.284),post hoc test analysis,in explicit task,pain stimuli and neutral stimuli evoked significant differences in LPP components(F_1,58=38.853,P<0.001,η_p²=0.401),the LPP evoked by pain stimuli was significantly greater than that of neutral stimuli（8.299±0.631μv vs 4.818±0.635μv）,and in implicit task,the difference between pain and neutral stimuli was not significant(F_1,58=0.791,P>0.05,η_p²=0.013).（4）Results of correlation analysis:in the correlation analysis between behavioral and EEG signals,a statistically significant correlation was found between the PCS（r=-0.310,P<0.05）and the N2 evoked by pain stimuli,and a statistically significant correlation was found between the behavioral index others pain intensity（r=-0.44,P<0.05）and the N2 evoked by pain stimuli meaningful correlation.There was a statistically significant correlation between the cognitive empathy（r=0.329,P<0.05）on the basic empathy scale and the LPP evoked by painful stimuli.Regarding the correlation between clinical characteristics of LBP and empathy,there was a statistically significant correlation between the PRI-A and self-unpleasantness scores（r=0.307,P<0.05）.there was a statistically significant correlation between the PRI（S+A）and self-unpleasantness scores（r=0.352,P<0.05）.the PRI-A（r=0.347,P<0.05）,PRI（S+A）（r=0.353,P<0.05）and emotional empathy all had statistically significant correlations.There was a statistically significant correlation between cognitive empathy and VAS scores（r=-0.381,P<0.05）.r=-0.320,P<0.05),PRI（r=-0.365,P<0.05）,VAS（r=-0.394,P<0.05）,and ODI（r=-0.305,P=0.051）were all correlated with the N2 evoked by painful stimuli.Conclusion:（1）Changes in emotional empathy in patients with CNLBP,which may lead to social dysfunction.（2）Pain perception and lumbar spine dysfunction significantly associated with changed emotional empathy in patients with CNLBP.（3）Early assessment of empathy for CNLBP can help us understand the emotional and cognitive disorder of CNLBP and provide new insights for clinical decision making by physicians and Physiotherapist.（4）The clinical rehabilitation of CNLBP should not only relieve the pain symptoms,but also consider the social and psychological factors of CNLBP and explore new intervention methods to better promote the“bio-psycho-social”comprehensive rehabilitation of CNLBP.