Prior exposure to others' facial expressions of pain can lead to a facilitation of pain responses, including its corresponding response channel, namely facial responses to pain. It has been questioned, however, whether this vicarious pain facilitation occurs only when observing others' pain or whether the observation of other negative expressions can trigger similar facilitation of facial responses to pain. The study aimed to test this, by comparing the impact of viewing others' facial expressions of pain versus another negative expression (sadness) and two control expressions (neutral, happiness) on facial responses to pain.
Participants (N = 56; 31 females), watched short video clips of computer-generated facial expressions (pain, sadness, neutral & happiness) before they received painful and non-painful heat stimuli. Facial responses were analysed using the Facial Action Coding System. In addition, subjective and autonomic responses were assessed.
The prior exposure to others' expressions of pain and sadness versus neutral did not lead to significantly increased facial responses to pain. Likewise, subjective and autonomic pain responses were not facilitated. However, viewing others' expressions of happiness, consistently reduced facial as well as subjective and autonomic responses to pain compared to others' negative or neutral expressions. This dampening effect was not observed for non-painful heat.
Facial and other pain responses were most strongly affected by prior exposure to others' facial expressions of happiness, which led to a pain-dampening effect. In contrast, the evidence for vicarious facilitation of pain was rather weak in the present study, with no evidence of pain-specificity.
Facial responses to pain – along with subjective and autonomic responses – are reduced when observing others' expressions of happiness, demonstrating pain modulation by positive affective social signals, which may also transfer to clinical contexts.
The central sensitization inventory (CSI) is a questionnaire that has been widely used as a tool for assessing symptoms associated with sensitization. However, its ability to identify individuals with this phenomenon has recently been questioned. The aim of this study was to assess the correlation of CSI with psychosocial and psychophysical factors in patients with painful TMD diagnosed according to diagnostic criteria for temporomandibular disorders (DC/TMD) and asymptomatic controls, as well as to determine the influence of these variables on the CSI scores variations.
This cross-sectional study with 77 patients diagnosed with painful TMD according to DC/TMD and 101 asymptomatic controls realized correlations between CSI, WUR, PPT, CPM and psychosocial questionnaires (HADS, PSQI, PCS and PSS). In cases where significant correlations existed, the potential influence of these variables on CSI variation was explored through linear regression analysis.
It has been found that the CSI correlates with psychosocial variables (anxiety, depression, catastrophizing, sleep and stress) (p < 0.0006) regardless of the presence of TMD, and that 68.9% of the variation in CSI scores can be influenced by all these variables (except stress). On the contrary, the CSI does not correlate with psychophysical parameters indicative of pain amplification (wind-up ratio and conditioned pain modulation) (p > 0.320).
CSI is more associated with psychosocial factors than with more robust indicators of probable central sensitization (CS), thus limiting its utility in detecting this phenomenon both in TMD patients and healthy individuals.
The research highlights a noteworthy relationship between the central sensitization inventory and psychological factors, emphasizing their substantial influence on inventory values. This correlation offers crucial insights into mental health markers within the questionnaire. Additionally, the lack of connection with pain amplification implies a necessary re-evaluation of the inventory's diagnostic suitability, especially in cases of painful temporomandibular disorders. Thus, caution is urged in its application for identifying CS in these individuals.
Spatial acuity concerns the ability to localize and discriminate sensory input and is often tested using the two-point discrimination threshold (2PDT). Sensitization of the pain system can affect the spatial acuity, but it is unclear how 2PDTs of different testing modalities are affected. The aim was to investigate if the 2PDTs for mechanical and heat stimulation at different intensities were modulated by topical capsaicin sensitization.
30 healthy subjects were divided into either a capsaicin or a placebo group. The 2PDT was tested using two different modalities, mechanical and thermal (laser) delivered at innocuous and noxious intensities. The 2PDT were determined at baseline and re-assessed 48 h later. In the follow-up session, the subjects either had a capsaicin patch (8%) or placebo patch placed in the testing area for 30 min before re-testing the 2PDT.
The 2PDT was highly dependent on stimulation modality and intensity. The lowest 2PDT was found for innocuous mechanical stimuli (40.0 mm, 95% CI 38.1–41.9 mm), and the highest 2PDT was found for innocuous thermal stimuli (81.7 mm, 95% CI 73.9–89.5 mm). Topical capsaicin generally increased the 2PDT, but this was only significant for innocuous mechanical stimuli. The perceived intensity of the stimuli was increased following capsaicin and was generally higher for noxious stimuli than for innocuous stimuli (ANOVA, p < 0.001).
This study showed that capsaicin provoked pain sensitization increased the 2PDT. The 2PDT tested using innocuous mechanical stimuli showed less variable results indicating that this test is most suitable to detect this aspect of spatial acuity.
This study investigated how the two-point discrimination threshold (2PDT) can be modulated by topical capsaicin. The 2PDT was assessed for two different modalities (thermal and mechanical) and for two different intensities (innocuous and noxious) before and after capsaicin. The results showed that the 2PDT was generally impaired following capsaicin, but this was only significant for mechanical innocuous stimuli. Furthermore, it was shown that mechanical innocuous stimuli assessed the 2PDT with lower variability than other combinations.
Only few previous cohort studies examined simultaneously predictors of chronic pain (CP) onset and recovery. Furthermore, these studies used various sociodemographic and pain-related characteristics, without standardized measures of sleep and depression. The present study aimed at expanding and strengthening these findings in a large Swiss population.
We analysed data from a longitudinal cohort (n = 4602) collected at two time points separated by 5 years in Lausanne, Switzerland. We studied through two independent multivariable logistic regression models, the predictors of CP onset and recovery, including socio-demographic data as well as standardized measures of sleep and mood.
Chronic pain was reported by 43.1% and 44.4% of participants, with 11.6% at the second follow-up reporting moderate or intense pain. Neuropathic pain, regardless of intensity, had a more negative impact on quality of life. An inferential model (n = 1331) identified the male sex as predictive for recovering from CP. Older age, being overweight or obese (compared to normal weight), higher depression scores and pain medication intake were predictive for sustained pain at the second follow-up. A second model (n = 1886) identified being overweight or obese (compared to normal weight), low quality of sleep and being a former smoker (compared to a non-smoker) as predictive for developing CP, while the male sex was lowering the risk.
While sex and weight are associated with both recovery and new CP onset, separate variables also need to be considered in these processes, underlining specific factors to be addressed, depending on the context, whether preventive or therapeutic.
Multivariable models in a Swiss cohort (N = 4602) associate male sex, not taking pain medication, normal weight, lower depression scores and younger age with recovery from chronic pain, while females, obese or overweight, having worse sleep and former smokers are associated with onset of new chronic pain. These common and separate factors need to be considered in treatment and prevention efforts.
Despite the use of Patient-Drawn Pain Drawings (PDPDs) in clinical settings, their validity as indicators of psychological distress remains debated. We aimed to assess the association between PDPD areas and physical health and psychological variables.
This study analysed digitally-drawn PDPDs from 15,345 chronic low back pain (LBP) patients at a Danish outpatient hospital unit. We employed a novel quantitative approach to calculate four log-transformed geometric pain areas for each PDPD. We assessed six psychological constructs and seven physical health variables. Associations were modelled using multivariable linear regression.
Increasing leg pain intensity (estimates from 0.12 to 0.25), disability (estimates from 0.3 to 0.14), and pain duration (estimates from 0.10 to 0.33) had the strongest associations with increasing pain areas. Conversely, increasing fear of movement (estimates from −0.02 to −0.05) and catastrophizing (estimates from −0.02 to −0.03) were associated with slight reductions in pain areas. Anxiety and depression had the weakest and most uncertain relationships to pain area size.
Increasing levels of leg pain intensity, pain duration, and pain-related disability were consistently associated with larger geometric pain areas in PDPDs. Conversely, the associations between the psychological constructs and the geometric pain areas exhibited varying directions and were notably weaker. Clinicians are encouraged to focus on the association of PDPDs with physical symptoms rather than psychological conditions during clinical assessments.
This large-scale study demonstrates that extensive pain areas in pain drawings drawn by LBP patients do not signify psychological distress. Our findings reveal that these pain representations are more closely linked to increased pain intensity, pain duration, and disability rather than being independently associated with psychological factors. Clinicians are encouraged to focus on the association of extensive pain areas with physical symptoms rather than psychological distress during clinical assessments.
Fabry disease (FD) is a rare X-linked lysosomal disorder caused by alpha-galactosidase deficiency consecutive to a pathogenic variant in the GLA gene. Age at onset is highly variable, with a wide clinical spectrum including frequent renal, cardiac, skin and nervous system manifestations. Since pain can be an indicator of underlying FD, we wanted to estimate the prevalence of FD in a population of chronic pain patients.
Two studies, DOUFAB and DOUFABIS, were carried out in expert centers for chronic pain to assess the prevalence of FD by measuring alpha galactosidase A activity in men and analysing the GLA gene in women.
Analysis of 893 patients, essentially adults, led to the diagnosis of FD in one female patient, now treated with enzyme replacement therapy.
The prevalence of FD is estimated about 1/1000 in our population of men and women suffering from various chronic pain. This is nearly the prevalence of FD observed in other previously screened high-risk populations with renal failure.
Although a systematic search for FD does not seem relevant in the context of unexplained chronic pain in adults, a positive family history of FD or the presence of additional FD related organ features must lead to consider this rare disease diagnosis. Therefore, pain specialists need to be aware of main features of FD, including pain characteristics.
Chronic pain is known to be an important construct in clinical practice and a particular form of chronic pain, high-impact chronic pain (HICP), has gained recent interest and attention by pain clinicians, epidemiologists, and clinical researchers. The purpose of our Topical Review is to describe the historical development of measures of HICP and to explore the psychometric properties of HICP as well as to present alternative measurement methods.
We identified strengths and weaknesses of the psychometric characteristics of HICP measures. Limitations of existing HICP measures were discussed and summarized and alternatives to current methods were proposed.
HICP operational definitions show variability across studies. All definitions cannot be correct, but which ones are incorrect cannot be determined as there is no gold standard. Random measurement error and recall bias are among the other limitations of current HICP measures. Model-based definitions of HICP, the discrete (for epidemiologic applications) and continuous (for clinical applications) latent variable models are discussed as likely superior alternatives to current methods.
Limitations of existing HICP methods are discussed and alternative development approaches to HICP measures are presented. The use of either discrete or continuous latent variable models would improve upon the psychometric characteristics of current HICP evidence. Examples are used to illustrate the benefits of latent variable models over traditional observed variable conceptualizations as the measurement of HICP continues to develop.
This work takes the position that current methods of measuring high impact chronic pain (HICP) likely contain substantial error. We have endorsed an alternative approach for several psychometrically grounded reasons. We recommend that future work consider the discrete latent variable framework for dichotomous measures of HICP and the continuous latent variable framework for continuous measures of HICP. The paper provides illustrative examples of these methods for a different patient reported measure that is lacking a gold standard, much like HICP measures.
Low back pain (LBP) is a leading reason for opioid use and a closer examination of opioid use and productivity losses among these patients is needed. We identify opioid use trajectories using a group-based trajectory model (GBTM) and estimate productivity losses across the trajectories.
Patients diagnosed with LBP in Swedish specialty care between 2011 and 2015, between the ages of 20 and 60, were included. Two GBTMs were estimated on monthly opioid use (converted to oral morphine equivalents) during the two 12-month periods preceding and following diagnosis. Productivity losses were estimated using the human-capital approach.
In total, 147,035 patients were included. The mean age at diagnosis was 43 years of age and 49% of the patients were male. A qualitative assessment of the identified groups in the GBTM models was made based on the patterns of opioid use. We chose three pre-diagnosis groups characterized as ‘Pre-low’ (N = 109,492), ‘Pre-increase’ (N = 27,336) and ‘Pre-high’ (N = 10,207). Similarly, four post-diagnosis groups were chosen and characterized as ‘Post-low’ (N = 73,287), ‘Post-decrease’ (N = 39,446), ‘Post-moderate’ (N = 20,001) and ‘Post-high’ (N = 13,595). Only 50% of the patients in the ‘Pre-high’ group were in the ‘Post-high’ group. The total productivity losses by the pre-diagnosis groups were more than 2.7 billion Euros over the total 6-year study period.
This study highlights how patients with LBP and high use of opioids are highly correlated before and after diagnosis. Patients with high use of opioids also exhibit high work absence and productivity losses.
This was the first study to estimate trajectories of opioids in the two time periods before and after a diagnosis of low back pain. For the first time, productivity losses were also estimated across the identified opioid use trajectories.
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