The Role of Childhood Trauma, PTSD Symptoms and Pain Coping Strategies in Individuals with Chronic and Acute Pain: A Strength-Based Approach

Introduction. Pain is classified as acute and chronic. Acute pain implies a painful condition with a rapid onset or of a short course, whereas chronic pain is referred to as a painful condition persisting beyond the normal time of healing. Chronic low back pain has also been correlated with stress-induced inflammation. Psychological distress aggravates pain symptoms and pain induces a stress response in the body by releasing cortisol from the adrenal cortex. The aim of the study. To investigate differences in levels of anxiety, depression, and cortisol blood concentration in patients with acute and chronic vertebral-sacral pain syndrome. Our main goal was to encrease our understanding of the development and persistence of acute and chronic back pain, define risk factors and improve treatment strategies for the patients. Materials and methods: We studied cortisol levels in blood plasma, levels of anxiety and depression in patients with back pain and LV-SI intravertebral disk herniation. The group under investigation included 125 patients, including 65 patients with acute, and 60 with chronic pain syndrome. A Visual Analogue Scale (VAS) was used to measure the patient`s pain assessment. Spielbergʼs anxiety test is designed to assess reactive and personal anxiety. Personal anxiety characterizes the degree of a person’s anxiety and emotional tension due to the action of stress factors in general. Reactive anxiety is a patient’s personal condition, which characterizes the degree of his anxiety, and emotional tension in response to the action of a stress factor. The Beck’s Depression Symptoms Questionnaire (BDSQ) includes 21 item, self-report rating inventory that measures characteristic attitudes and symptoms of depression. Results. We found no significant difference according to VAS between groups, at the time of hospitalization, patients in the acute pain group evaluated their pain as 7.15 ± 1.17 points, while in the chronic pain group it was estimated as 6.08 ± 0.96 points (p-value more than 0.05). The concentration of cortisol in blood plasma in the acute pain group patients was 313.3 ± 87.7 mmol/l, and in the chronic pain group – 450.7 ± 121.9 mmol/l, the difference between the groups was insignificant (p-value more than 0.05). The evaluation according to Spielbergʼs anxiety test demonstrated high anxiety levels at the time of examination: in the acute pain group reactive anxiety corresponded to 40.4 ± 12.6 points, in the chronic pain group the same index was 39.5 ± 11.3. Personal anxiety in the group of acute pain was 32.3 ± 13.6, in the group of chronic pain – 41.3 ± 9.7. According to Beck’s Depression Symptoms Questionnaire before the beginning of treatment average score in the acute pain group was estimated as 6.8 ± 1.1 points, while in the chronic pain group this index corresponded to 9.8 ± 0.8 points (probable difference between groups p-value less than 0.05). Comparisons of cortisol concentrations between groups of patients with different levels of pain, anxiety, and depression demonstrated no significant differences. However, cortisol level was higher in the acute pain group among patients who rated their pain syndrome as ʺsevere painʺ (6-7 points according to VAS) (280.2 ± 77.8 mmol/l in the group of acute pain, and 515.0 ± 80.1 mmol/l in the group of chronic pain), as well as among patients with mild depressive symptoms (393.5 ± 19.5 mmol/l in the group with an acute pain compared to 553.1± 68.0 mmol/l in the group with chronic pain syndrome). Conclusions. The study demonstrates differences in pain perception and assessment in patients that suffer from acute and chronic back pain. A high level of personal and reactive anxiety was found among participants. A higher level of depressive symptoms, as well as the disturbances in the diurnal fluctuations of cortisol were detected in the chronic pain group patients.

The aim. The primary aim of this study is to assess the variance in substance P concentration, taking into account pain intensity and the presence of a neuropathic component, among patients experiencing acute and chronic vertebral lumbosacral pain syndromes. Materials. Measurement of substance P concentration in serum blood, evaluation of pain syndrome using the VAS scale, and assessment of pain according to the DN4 questionnaire were performed in patients receiving comprehensive treatment. A total of 125 patients were included in the study, comprising 65 patients with acute pain and 60 patients with chronic pain syndrome. Results. Pain ratings according to the Visual Analog Scale (VAS) among patients from the acute pain group was 7.15±1.07 on the VAS scale, while patients in the chronic pain group rated it at 6.09±0.96. On the 7th day of treatment, patients in the acute pain group reported a pain rating of 4.46±0.73, whereas those in the chronic pain group reported a rating of 4.22±0.97. The level of substance p(SP) in serum blood on the first day of treatment was 13.96±1.93 ng/mL in the acute pain group and 10.34±2.92 ng/mL in the chronic pain group. By the 7th day of treatment, the level decreased to 7.72±1.90 ng/mL in the acute pain group and 8.03±2.14 ng/mL in the chronic pain group. According to the DN4 questionnaire, neuropathic component was ascertained in 38% of patients with acute pain syndrome and 56% of participants with chronic pain. The average DN4 score in the acute pain group was 2.26±1.01, while in the chronic pain group, it was 4.53±1.02. In the group of patients with chronic pain syndrome and the presence of a neuropathic component, the level of SP was 10.89±1.78 ng/mL. In contrast, without the presence of a neuropathic component, it was 6.51±1.94 ng/mL. Conclusions. The trajectory of acute and chronic pain syndromes in patients with lumbosacral vertebral pain syndromes exhibits dissimilarities. Patients experiencing acute pain displayed a more favorable trend characterized by a reduction in pain intensity and a decrease in pain-related neurotransmitter concentration in the bloodstream.

Diverse approaches exist for diagnosing and treating patients afflicted with acute and chronic low back pain syndromes (LBP), thereby necessitating a comprehensive evaluation of the pain syndrome and a meticulous analysis of the neuropathic component to enhance our scholarly comprehension of the distinct differences in pain progression among these individuals. A total of 125 individuals (56 females and 69 males) diagnosed with vertebral lumbar pain syndromes (LBP), aged between 20 and 68 years (42.8 ± 11.1 years), underwent comprehensive evaluation. Stratification into two distinct groups was based on the duration of the pain syndrome: an acute pain group (pain lasting up to 3 months) and a chronic pain group (pain persisting beyond 3 months). Pain assessment, administered upon hospitalization, involved utilizing of well-established tools such as the Visual Analogue Scale (VAS), DN4 Questionnaire, and McGill Pain Questionnaire. The initial pain intensity, measured by VAS upon admission, was recorded as 7.15 ± 1.17 in the acute pain group and 6.08 ± 0.96 in the chronic pain group. Analysis of responses to the DN4 questionnaire revealed that patients with acute pain syndrome obtained an average score of 2.26 ± 1.01, whereas those in the chronic pain group scored 4.53 ± 1.02. The presence of a neuropathic component was identified in 38 % of patients with acute pain and 56 % of patients with chronic pain. Correlational analyses indicated a weak positive correlation (r = 0.12, p < 0.05) between VAS scores and the assessment of neuropathic pain using the DN4 questionnaire in the acute pain group. However, the chronic pain group observed a moderate positive correlation (r = 0.41, p < 0.001). Patients experiencing chronic LBP expressed their pain sensations in a more emotionally descriptive manner. Notably, the chronic pain group exhibited a statistically significant elevation in the number of selected descriptors according to the Index of Chosen Descriptors (ICD) on the sensory scale, as well as an increased Pain Rank Index (PRI) on both sensory and affective scales, compared to the acute pain group. To summarize, individuals with chronic LBP exhibit a more prevalence of the neuropathic component. Moreover, patients in the chronic pain group demonstrated higher scores indicative of sensory and psychosocial aspects of pain. Key words: acute pain, chronic pain, neuropathic component of pain, verbal descriptors, McGill Pain Questionnaire

An observational study of pain self-management strategies and outcomes: does type of pain, age, or gender, matter?

Chronic pain in multiple sclerosis is common and difficult to treat. Its mechanisms remain incompletely understood. Dysfunction of the descending pain modulatory system is known to contribute to human chronic pain conditions. However, it is not clear how alterations in executive function influence this network, despite healthy volunteer studies linking function of the descending pain modulatory system, to cognition. In adults with multiple sclerosis-associated chronic neuropathic limb pain, compared to those without pain, we hypothesized altered functional connectivity of the descending pain modulatory system, coupled to executive dysfunction. Specifically we hypothesized reduced mental flexibility, because of potential importance in stimulus reappraisal. To investigate these hypotheses, we conducted a case-control cross-sectional study of 47 adults with relapsing remitting multiple sclerosis (31 with chronic neuropathic limb pain, 16 without pain), employing clinical, neuropsychological, structural, and functional MRI measures. We measured brain lesions and atrophy affecting descending pain modulatory system structures. Both cognitive and affective dysfunctions were confirmed in the chronic neuropathic limb pain group, including reduced mental flexibility (Delis Kaplan Executive Function System card sorting tests P < 0.001). Functional connectivity of rostral anterior cingulate and ventrolateral periaqueductal gray, key structures of the descending pain modulatory system, was significantly lower in the group experiencing chronic neuropathic pain. There was no significant between-group difference in whole-brain grey matter or lesion volumes, nor lesion volume affecting white matter tracts between rostral anterior cingulate and periaqueductal gray. Brainstem-specific lesion volume was higher in the chronic neuropathic limb pain group (P = 0.0017). Differential functional connectivity remained after correction for brainstem-specific lesion volume. Gabapentinoid medications were more frequently used in the chronic pain group. We describe executive dysfunction in people with multiple sclerosis affected by chronic neuropathic pain, along with functional and structural MRI evidence compatible with dysfunction of the descending pain modulatory system. These findings extend understanding of close inter-relationships between cognition, function of the descending pain modulatory system, and chronic pain, both in multiple sclerosis and more generally in human chronic pain conditions. These findings could support application of pharmacological and cognitive interventions in chronic neuropathic pain associated with multiple sclerosis.

BackgroundChronic pain in sickle cell disease (SCD) can begin in adolescence and impair quality of life (QOL) and functioning; however, very few studies have characterized chronic SCD-related pain in this age group. This study aimed to examine the sensory, inflammatory, and psychosocial characteristics of chronic pain in adolescents and young adults (AYA) with SCD and compare them according to the three ACTTION-APS Pain Taxonomy subtypes of chronic SCD pain.MethodA cross-sectional comparative design of AYA ages 9-23 with chronic SCD pain and pain-free AYA with SCD was used. Quantitative sensory testing (QST) and psychosocial questionnaires were administered and analyzed using independent t-tests to detect differences between chronic pain and pain-free groups and analysis of variance was used to test differences between chronic pain subtypes. Salivary samples were collected for analysis of inflammatory markers IL-1β, 6, 8, 10, and TNF-α using standardized enzyme-linked immunosorbent assay kits.ResultsNineteen chronic pain participants and four pain-free controls were enrolled. Participants with chronic SCD-related pain had a significantly higher pain burden, higher mechanical pain threshold, and lower warm detection threshold (WDT) compared with pain-free AYA with SCD. Statistical differences among the three chronic pain groups and the pain-free control group in psychosocial measures and WDT were also noted.DiscussionThe findings of this study can help nurses understand chronic pain in SCD youth. This study suggests that there are unique characteristics of chronic SCD-related pain in youth with varying disabilities and psychosocial needs; additional research is needed to explore these differences further.

BackgroundConsumer-grade wearables, such as Fitbits, are a promising, cost-effective methodology for objectively assessing sleep and physical activity in youth with pain.ObjectiveThis study investigated the acceptability and feasibility of implementing Fitbits for youth with acute and chronic pain in and out of hospital settings while maintaining data security and patient confidentiality.MethodsWe investigated participant experience of Fitbit use over 3 to 4 weeks for a sample of youth with acute pain undergoing either orthopedic or cardiac surgical procedures (N=34, mean age 14.46, SD 3.70 years, 47.06% [n=36] female) and a sample of youth with chronic pain enrolled in an intensive interdisciplinary pain treatment program (N=28, mean age 15.00, SD 2.33 years, 82.14% [n=23] female). We assessed the acceptability of Fitbit use through survey items probing comfort (0=extremely uncomfortable to 10=extremely comfortable), perceived burdensomeness (0=not burdensome at all to 10=extremely burdensome), and open-ended issues or concerns. Feasibility was assessed by tracking the daily compliant wear of the Fitbit device, which was operationalized as more than 600 minutes of daily wear time. We tested for group differences in acceptability and feasibility between orthopedic and cardiac patients within the acute pain sample and between the acute pain and chronic pain samples. We created an automated data pipeline to ensure data security, patient confidentiality, and quality.ResultsAcceptability findings revealed high levels of reported comfort (acute pain: mean 8.56, SD 1.43; chronic pain: mean 8.27, SD 1.69) and low levels of perceived burdensomeness (acute: mean 0.68, SD 1.17; chronic: mean 1.15, SD 1.38) related to Fitbit wearing in both samples. No significant differences in these acceptability outcomes emerged between orthopedic and cardiac patients or between the acute pain and chronic pain groups (P values>.10). Transient concerns of mild wrist irritation and sleep discomfort were occasionally reported across both samples (15.79% [n=9] of participants). Feasibility findings indicated high feasibility (acute: median compliance rate of 86.67%; chronic: median compliance rate of 96.65%) for the study duration in both samples. Mann-Whitney U tests indicated significantly higher median compliance rates per participant among orthopedic as compared with cardiac patients (U=146.5, P=.04) and significantly higher median compliance rates per participant among the chronic pain group as compared with the acute pain group (U=186, P<.001), including significantly higher median compliant days (U=162, P<.001) and study days (U=234.5, P<.001) per participant.ConclusionsThese findings support the use of Fitbits as an acceptable and feasible method for collecting objective data on sleep and physical activity for youth experiencing pain. Findings also highlight the logistics of implementing consumer-grade wearable devices throughout all stages of the clinical research process.

Context: Prescription opioid abuse and misuse is a significant public health crisis. In 2012, an opioid prescribing pathway for patients with chronic pain presenting to the Emergency Department (ED) was implemented. The objective of this study is to determine the impact of the pathway for administration of opioids in the ED as well as the prescribing of opioids for home use after discharge.Methods: Retrospective pre- and post-intervention time series study of consecutive patients presenting to the ED with acute and chronic pain complaints before and after implementation of the pathway. For the purposes of this study, we included patients with chronic abdominal or back pain – defined as pain present for greater than three months – and acute pain as acute long bone fracture.Results: Before pathway implementation, there was no statistically significant difference in the mean morphine equivalent (MEQ) dose administered for chronic or acute pain patients. After pathway implementation, there was a decrease in IV/IM morphine administered to patients with chronic pain (p = .0200) but not to patients with acute pain (p = .0820). Overall, MEQs administered did not change in either group. In the acute pain group, no significant differences were found in the number of patients who received opioid prescriptions upon discharge (p = .7749). However, in the chronic pain group, the number of patients who received opioid prescriptions upon discharge decreased with statistical significance (p = .0017).Conclusions: After the implementation of a chronic pain management pathway in an ED, there is a decrease noted in opioids administered to patients with chronic pain both in the ED and prescriptions on discharge. In patients presenting with acute pain, there was no change in administration or prescription of opioids.

Recent factor analytic investigations of post-traumatic stress disorder in military veterans suggest that symptoms are best described by either a hierarchical 2-factor model or a 4-factor inter-correlated model. Other recent evidence suggests that post-traumatic stress disorder and chronic pain are intricately related; however, the nature of this relationship is not well understood. Factor analysis provides one method for clarifying this relationship. In study 1, we compared competing models of post-traumatic stress disorder symptom structure in a sample of 400 male United Nations peacekeepers using confirmatory factor analysis. Results indicated that both the hierarchical 2-factor and the 4-factor inter-correlated models provided good fit to the data. In study 2, the reliability of these models was assessed in 427 male United Nations peacekeepers with chronic back pain and 341 without. Group comparisons of the confirmatory factor analysis results revealed that the structure of the hierarchical 2-factor and 4-factor inter-correlated models both provided good fit to the data in both the chronic back pain and the group without. However, the structure of the models for the group with chronic back pain group differed in significant ways from that of the group without chronic back pain. Post-traumatic stress disorder symptoms in military veterans can be adequately conceptualized using either a hierarchical 2-factor or 4-factor inter-correlated model. Chronic pain has a minimal influence on overall factor structure. The hierarchical 2-factor model, while parsimonious, does not provide the degree of symptom detail provided by the 4-factor inter-correlated model. Implications for conceptualization of post-traumatic stress disorder symptoms for patients with chronic back pain and significant post-traumatic stress disorder symptomatology are discussed.

Longitudinal analyses of the influence of chronic pain on pain-related regional brain volumes in general populations are warranted. This prospective cohort study investigated the association between the presence of chronic pain at baseline and the subsequent changes in pain-related regional brain volumes among Japanese community-dwelling older residents. Participants aged 65 years or older who underwent brain magnetic resonance imaging (MRI) scans in both 2012 and 2017 were included. According to the presence or absence of chronic pain (defined as pain lasting for longer than 3 months) in 2012, participants were categorized into a 'chronic pain' group and 'no chronic pain' group. Region-of-interest analyses for the ventrolateral prefrontal cortex, dorsolateral prefrontal cortex, orbitofrontal cortex, postcentral gyrus, insular cortex, thalamus, anterior cingulate cortex, posterior cingulate cortex, amygdala and hippocampus were performed using FreeSurfer software. Whole-brain analysis was conducted by voxel-based morphometry. Rates of change in regional brain volume at 5 years after baseline were estimated using analysis of covariance. Among the 766 participants included in the FreeSurfer analysis, 444 (58%) were female and 287 (37%) were categorized into the chronic pain group. The results of FreeSurfer analysis showed that the chronic pain group had significantly greater decreases in regional volume in the postcentral gyrus (-2.187% in the chronic pain group versus -1.681% in the no chronic pain group, P = 0.01), thalamus (-4.400% versus -3.897%, P = 0.006), anterior cingulate cortex (-2.507% versus -1.941%, P = 0.004) and amygdala (-4.739% versus -4.022%, P = 0.03) compared to the no chronic pain group after adjusting for age, sex, education attainment, marital status, hypertension, diabetes, serum total cholesterol level, body mass index, current smoking, current drinking, regular exercise, cerebrovascular lesions on MRI, activities in daily living disability and depressive symptoms. Among the 730 participants included in the voxel-based morphometry analysis, 433 (59%) were female and 272 (37%) were categorized into the chronic pain group. The voxel-based morphometry analysis showed that the chronic pain group had a significantly greater regional volume decrease in the right anterior insula than the no chronic pain group. Our findings suggest that the presence of chronic pain at baseline is associated with a significantly greater decrease in the volume of pain-related brain regions at 5 years after baseline in community-dwelling older Japanese.

The insufficient knowledge of biochemical mechanisms behind the emergence andmaintenance of chronic musculoskeletal pain conditions constrains thedevelopment of diagnostic and therapeutic tools for clinical use. However,physical activity and exercise may improve pain severity and physical functionduring chronic pain conditions. Nevertheless, the biochemical consequences ofphysical activity and exercise in chronic pain need to be elucidated to increasethe precision of this therapeutic tool in chronic pain treatment. Theendocannabinoid system has been suggested to play an important role inexercise-induced reward and pain inhibition. Moreover, glutamatergic signallinghas been suggested as an important factor for sensation and transmission ofpain. In addition, a link has been established between the endocannabinoidsystem and glutamatergic pathways. This study examines the effect of dynamicload arm cycling (30 min) on levels of lipid mediators related to theendocannabinoid system and glutamate in plasma of chronic pain subjects andpain-free controls. Pain assessments and plasma levels ofarachidonoylethanolamide (anandamide), 2-aracidonoylglycerol,oleoylethanolamide, palmitoylethanolamide, stearoylethanolamide and glutamatefrom 21 subjects with chronic neck pain (chronic pain group) and 11 healthycontrols were analysed pre and post intervention of dynamic load arm cycling.Pain intensity was significantly different between groups pre and post exercise.Post exercise, anandamide levels were significantly decreased in health controlsbut not in the chronic pain group. A strong positive correlation existed betweenanandamide and glutamate in the control group post exercise but not in thechronic pain group. Moreover, the glutamate/anandamide ratio increasedsignificantly in the control group and differed significantly with the chronicpain group post exercise. The altered relationship between anandamide andglutamate after the intervention in the chronic pain group might reflectalterations in the endocannabinoid-glutamate mechanistic links in the chronicpain group compared to the pain-free control group.

Traumatic brain injury (TBI) can lead to a variety of comorbidities, including chronic pain. Although brain tissue metabolite alterations have been extensively examined in several chronic pain populations, it has received less attention in people with TBI. Thus, the primary aim of this study was to compare brain tissue metabolite levels in people with TBI and chronic pain (n = 16), TBI without chronic pain (n = 17), and pain-free healthy controls (n = 31). The metabolite data were obtained from participants using whole-brain proton magnetic resonance spectroscopic imaging (1H-MRSI) at 3 Tesla. The metabolite data included N-acetylaspartate, myo-inositol, total choline, glutamate plus glutamine, and total creatine. Associations between N-acetylaspartate levels and pain severity, neuropathic pain symptom severity, and psychological variables, including anxiety, depression, post-traumatic stress disorder (PTSD), and post-concussive symptoms, were also explored. Our results demonstrate N-acetylaspartate, myo-inositol, total choline, and total creatine alterations in pain-related brain regions such as the frontal region, cingulum, postcentral gyrus, and thalamus in individuals with TBI with and without chronic pain. Additionally, NAA levels in the left and right frontal lobe regions were positively correlated with post-concussive symptoms; and NAA levels within the left frontal region were also positively correlated with neuropathic pain symptom severity, depression, and PTSD symptoms in the TBI with chronic pain group. These results suggest that neuronal integrity or density in the prefrontal cortex, a critical region for nociception and pain modulation, is associated with the severity of neuropathic pain symptoms and psychological comorbidities following TBI. Our data suggest that a combination of neuronal loss or dysfunction and maladaptive neuroplasticity may contribute to the development of persistent pain following TBI, although no causal relationship can be determined based on these data.

Characteristics of a Chronic Pain Phenotype in Adults with Sickle Cell Disease

Low peak alpha frequency (PAF) is an electroencephalography (EEG) outcome associated reliably with high acute pain sensitivity. However, existing research suggests that the relationship between PAF and chronic pain is more variable. This variability could be attributable to chronic pain groups typically being examined as homogenous populations, without consideration being given to potential diagnosis-specific differences. Indeed, while emerging work has compared individuals with chronic pain to healthy controls, no previous studies have examined differences in PAF between diagnoses or across chronic pain subtypes. To address this gap, we reanalysed a dataset of resting state EEG previously used to demonstrate a lack of difference in PAF between individuals with chronic pain and healthy controls. In this new analysis, we separated patients by diagnosis before comparing PAF across three subgroups: chronic widespread pain (n = 30), chronic back pain (n = 38), and healthy controls (n = 87). We replicate the original finding of no significant difference between chronic pain groups and controls, but also find that individuals with widespread pain had significantly higher global average PAF values than those of people with chronic back pain [p = 0.028, β = 0.25 Hz] after controlling for age, sex, and depression. These novel findings reveal PAF values in individuals with chronic pain may be diagnosis-specific and not uniformly shifted from the values of healthy controls. Future studies should account for diagnosis and be cautious with exploring homogenous 'chronic pain' classifications during investigations of PAF. Our work suggests that, contrary to previous hypotheses, inter-individual differences in PAF reflect diagnosis-specific mechanisms rather than the general presence of chronic pain, and therefore may have important implications for future work regarding individually-tailored pain management strategies.

Conditioned pain modulation (CPM) is a measurement of the descending pain pathways that inhibit or facilitate afferent noxious stimuli. The reliability of CPM in older individuals with or without chronic musculoskeletal pain has not been sufficiently reported. This study aimed to examine the inter-session reliability of CPM in these cohorts and the factors in CPM reliability. Individuals aged 65 or older were recruited in Narita, Japan. The measurements were performed on separate days 2 weeks apart (sessions 1 and 2). Each participant's hand was immersed in cold water, and we measured pressure pain threshold (PPT) before and after the immersion. The ratio before and after PPT measurements was presented as CPM index. The autonomic activities (heart rate variability, heart rate, and blood pressure) were simultaneously measured. An absolute reliability of CPM index was analyzed by the adjusted two-way analysis of variance (ANOVA) and the Bland Altman plot, and relative reliability was analyzed by intraclass correlation coefficient (ICC). Spearman's rho correlation and the adjusted multivariate regression analysis were utilized for examining the CPM reliability factors. Thirty-two participants were divided into two groups: chronic pain (n=19) and non-chronic pain (n=13) groups. The mean difference between session 1 and 2 in CPM index showed a systematic error in the chronic pain group at 17.3 (confidence interval, CI: 15.0 to 19.7), but none in the non-chronic pain group at 3.7 (CI: -0.02 to 7.4). The adjusted two-way ANOVA for CPM index did not identify any differences. ICC was not significant at p=-0.247 in the non-chronic and 0.167 in chronic pain. Multivariate regression analysis revealed total power and low/high frequencies as significant factors for CPM index. This study identified low inter-session reliability in older adults with chronic musculoskeletal pain and autonomic nervous system activities as factors in CPM reliability.