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The aim of this systematic review was to evaluate the effect of visual feedback techniques on pain perception by analysing the effect of normal-sized, magnified or minified visual feedback of body parts on clinical and experimentally-induced pain. Databases searched: Medline, Embase, PsychInfo, PEDro, CINAHL, CENTRAL and OpenSIGLE. Studies investigating pain patients and pain-free participants exposed to experimentally-induced pain were analysed separately. Risk of bias was assessed and data were meta-analysed. Thirty four studies were included. A meta-analysis of clinical data favoured mirror visual feedback (six trials; mean difference = -13.06 mm; 95% CI = -23.97, -2.16). Subgroup analysis favoured mirror visual feedback when used as a course of treatment (three trials; mean difference = -12.76 mm; 95% CI = -24.11, -1.40) and when used for complex regional pain syndrome for complex regional pain syndrome (three trials; standard mean difference = -1.44; 95% CI = -1.88, -0.99). There is insufficient evidence to determine differences between normal-sized view and a size-distorted view of the limb. Mirror visual feedback was not superior to object view or direct view of the hand for reducing experimental pain in pain-free participants. There were inconsistencies in study findings comparing normal-sized reflection of a body part and a reflection of an object, or a magnified or minified reflection. There is tentative evidence that mirror visual feedback can alleviate pain when delivered as a course of treatment, and for patients with complex regional pain syndrome. It was not possible to determine whether normal-sized, magnified or minified visual feedback of body parts affects pain perception because of contradictory findings in primary studies., Significance: It was not possible to determine whether normal-sized, magnified or minified visual feedback of body parts affected pain perception in clinical or experimental settings because of contradictory findings in primary studies. This emphasizes the need for higher quality studies., (© 2017 European Pain Federation - EFIC®.)

Background: Studies suggest that observing magnified and minified body parts using mirrors, lenses and virtual reality may affect pain perception. However, the direction of effect varies between studies. The aim of the present study was to evaluate the effect of observing a normal-sized, magnified and minified reflection of a hand on perceptual embodiment and contact-heat stimuli., Methods: Participants (n = 46) observed a normal-sized, magnified and minified reflection of the hand and a no-reflection condition while performing synchronized finger movements for 3 min (adaptive phase). Measurements of embodiment were taken before adaptive phase, pre- and post-contact-heat stimuli., Results: There were no differences in pain threshold nor tolerance between reflection and no-reflection conditions. Altering the size of the reflection of the hand did not affect estimates of pain threshold nor tolerance. The temperature for warm detection threshold was lower when participants were observing the magnified reflection of the hand compared with the no-reflection condition. Perceptual embodiment of the reflection of the hand was stronger after an adaptive phase with visuo-motor feedback, and the painful stimuli did not weaken the perceptual experience., Conclusion: Observing a reflection of the hand in front of a mirror did not alter heat pain threshold nor tolerance when compared with a no-reflection condition, and altering the size of the reflection did not affect pain perception. Researchers and clinicians using visual feedback techniques may consider including an adaptive phase with visuo-motor feedback to facilitate embodiment of the viewed body part., Significance: An adaptive phase with visuo-motor feedback enhances the perceptual experience of embodiment of a reflection of a hand and a painful stimulus does not weaken the experience. This should be considered when using visual feedback techniques for pain management., (© 2017 European Pain Federation - EFIC®.)

Background: The aim of this study was to investigate the influence of body fat percentage and its distribution on sensory detection and pain sensitivity responses to experimentally induced noxious stimuli in otherwise pain-free individuals., Methods: Seventy-two participants were divided into three equal groups according to their body mass index (BMI: normal, overweight and obese). Percentage body fat was estimated using a four-site skinfold method. Measurements of cold pressor pain threshold, tolerance and intensity; contact thermal sensory detection and heat pain threshold and tolerance (TSA-II - NeuroSensory Analyzer, Medoc); and blunt pressure pain threshold (algometer, Somedic SenseLab AB) were taken at the waist and thenar eminence., Results: Mean ± SD pressure pain threshold of the obese group (620.72 ± 423.81 kPa) was significantly lower than normal (1154.70 ± 847.18 kPa) and overweight (1285.14 ± 998.89 kPa) groups. Repeated measures ANOVA found significant effects for site for cold detection threshold (F 1,68  = 8.3, p = 0.005) and warm detection threshold (F 1,68  = 38.69, p = 0.001) with waist having lower sensory detection thresholds than thenar eminence. For heat pain threshold, there were significant effects for site (F 1,68  = 4.868, p = 0.031) which was lower for waist compared with thenar eminence (mean difference = 0.89 °C)., Conclusion: Obese individuals were more sensitive than non-obese individuals to pressure pain but not to thermal pain. Body sites may vary in their response to different types and intensities of stimuli. The inconsistency of findings within and between research studies should catalyse further research in this field., Significance: This study provided evidence that body mass index and distribution of body fat can influence sensory detection and pain sensitivity. Obese individuals were more sensitive than normal range body mass index individuals to pressure pain but not to thermal pain. Pain response varied according to subcutaneous body fat at different body sites. These findings strengthen arguments that weight loss should be a significant aspect of a pain management programme for obese pain patients., (© 2017 Crown copyright. European Journal of Pain © 2017 European Pain Federation - EFIC®.)

Literature suggests that pain perception diminishes in old age. The most recent review used search strategies conducted over a decade ago and concluded that study findings were equivocal. The aim of this systematic review, with meta-analysis, was to determine age-related changes in pain sensitivity in healthy pain-free adults, children and adolescents. A search of PubMed, Science Direct, and PsycINFO identified studies that compared pain sensitivity response to noxious stimuli at different time points in the lifespan of healthy individuals. Selected studies were assessed for methodological quality and data pooled and meta-analysed. Publication bias was tested using Funnel plots. Twelve studies were included in the review (study sample sizes 30-244 participants). Seven of nine studies found statistically significant differences in pain sensitivity response between old (mean ± SD 62.2 ± 3.4 to 79 ± 4 years) and younger adults (22 ± 1.5 to 39.1 ± 8.8 years), but the direction of change was inconsistent. Meta-analysis found that pressure pain threshold was lower in old adults compared with younger adults (p = 0.018, I 2  = 60.970%). There were no differences in contact heat pain thresholds between old and younger adults (p = 0.0001, I 2  = 90.23%). Three studies found that younger children (6-8.12 years) were more sensitive to noxious stimuli than older children (9-14 years). Methodological quality of studies was high, with a low risk of publication bias. There was substantial statistical and methodological heterogeneity. There is tentative evidence that pressure pain threshold was lower in old adults compared with younger adults, with no differences in heat pain thresholds. Further studies are needed., Significance: There is tentative evidence that old adults may be more sensitive to mechanically-evoked pain but not heat-evoked pain than young adults. There is a need for further studies on age-related changes in pain perception., (© 2017 European Pain Federation - EFIC®.)

Background: Gender role expectations of pain (GREP) have been shown to mediate sex differences in experimental pain. Few studies have investigated the role of ethnicity in shaping GREP. The aim of this study was to examine interactions between ethnicity and GREP on experimentally induced pressure and ischaemic pain in Libyan and white British students in their respective countries., Methods: Libyan (n = 124) and white British (n = 51) students completed a GREP questionnaire and their response to experimental pain was measured. Blunt pressure pain threshold (PPT) was measured over the 1st interosseous muscle using algometry. Pain intensity and pain unpleasantness (100 mm visual analogue scale) were measured at 1-min intervals during a submaximal effort tourniquet test on the forearm., Results: Multivariate analysis of variance detected significant effects for Sex and Ethnicity on pain measurements. Men had higher PPTs than women (p < 0.001). Libyans had higher PPTs than white British participants (p < 0.001). There were significant effects for Sex and Ethnicity for pain intensity ratings (p < 0.01) but no significant differences between the sexes in pain unpleasantness (p > 0.05). Libyan participants had higher pain intensity (p < 0.01) and pain unpleasantness (p < 0.05) ratings compared with white British participants. There were effects for Sex and Ethnicity for all GREP dimensions. Libyan participants exhibited stronger stereotypical views in GREP than white British participants (p < 0.001)., Conclusions: GREP was the mediator of sex but not ethnic differences in pain report, suggesting that gender stereotypical attitudes to pain account for differences in pain expression between men and women., (© 2012 European Federation of International Association for the Study of Pain Chapters.)

Gender role refers to the culturally and socially constructed meanings that describe how women and men should behave in certain situations according to feminine and masculine roles learned throughout life. The aim of this meta-analysis was to evaluate the relationship between gender role and experimental pain responses in healthy human participants. We searched computerized databases for studies published between January 1950 and May 2011 that had measured gender role in healthy human adults and pain response to noxious stimuli. Studies were entered into a meta-analysis if they calculated a correlation coefficient (r) for gender role and experimental pain. Searches yielded 4465 'hits' and 13 studies were eligible for review. Sample sizes were 67-235 participants and the proportion of female participants was 45-67%. Eight types of gender role instrument were used. Meta-analysis of six studies (406 men and 539 women) found a significant positive correlation between masculine and feminine personality traits and pain threshold and tolerance, with a small effect size (r = 0.17, p = 0.01). Meta-analysis of four studies (263 men and 297 women) found a significant negative correlation between gender stereotypes specific to pain and pain threshold and tolerance, with a moderate effect size (r = -0.41, p < 0.001). In conclusion, individuals who considered themselves more masculine and less sensitive to pain than the typical man showed higher pain thresholds and tolerances. Gender stereotypes specific to pain scales showed stronger associations with sex differences in pain sensitivity response than masculine and feminine personality trait scales., (© 2012 European Federation of International Association for the Study of Pain Chapters.)

Previous studies found a relationship between response to experimentally-induced pain and scores for the gender role expectations of pain (GREP) questionnaire. Findings were similar in individuals from America, Portugal and Israel suggesting that gender role expectations may be universal. The aim of this study was to translate and validate Arabic GREP using Factor Analysis and to investigate if sex differences to cold-pressor pain in healthy Libyan men and women are mediated through stereotypical social constructs of gender role expectations and/or pain-related anxiety. One hundred fourteen university students (58 women) underwent two cycles of cold pressor pain test to measure pain threshold, tolerance, intensity, and unpleasantness. Participants also completed the Arabic GREP questionnaire and the Pain Anxiety Symptom Scale-Short form (PASS-20). It was found that Libyan men had higher pain thresholds and tolerances than women (mean difference, 95% CI: threshold = 4.69 (s), -0.72 to 10.1, p = 0.005; tolerance = 13.46 (s), 0.5-26.4, p = 0.018). There were significant differences between sexes in 6 out of 12 GREP items (p < 0.004 after Bonferonni adjustment). The results of mediational analysis showed that GREP factors were the mediators of the effects of sex on pain threshold (z = -2.452, p = 0.014 for Self Sensitivity); (z = -2.563, p = 0.01, for Self Endurance) and on pain tolerance (z = -2.538, p = 0.01 for Self Endurance). In conclusion, sex differences in response to pain were mediated by gender role expectations of pain but not pain-related anxiety., (© 2011 European Federation of International Association for the Study of Pain Chapters.)

Aim: We investigated the literature of randomised placebo-controlled trials to find out if transcutaneous electrical nerve stimulation (TENS) or acupuncture-like transcutaneous electrical nerve stimulation (ALTENS) can reduce analgesic consumption after surgery., Results: Subgroup analysis for adequate treatment (pulse frequency: 1-8Hz [ALTENS] or 25-150Hz [TENS], current intensity: "strong, definite, subnoxious, maximal tolerable" or above 15mA, and electrode placement in the incision area) were performed. Twenty-one randomised, placebo-controlled trials with a total of 1350 patients were identified. For all trials, the mean reduction in analgesic consumption after TENS/ALTENS was 26.5% (range -6 to +51%) better than placebo. Eleven of the trials compromising 964 patients, had reports which stated that a strong, subnoxious electrical stimulation with adequate frequency was administered. They reported a mean weighted reduction in analgesic consumption of 35.5% (range 14-51%) better than placebo. In nine trials without explicit confirmation of sufficient current intensity and adequate frequency, the mean weighted analgesic consumption was 4.1% (range -10 to +29%) in favour of active treatment. The difference in analgesic consumption was significantly (p=0.0002) in favour of adequate stimulation. The median frequencies used in trials with optimal treatment was 85Hz for TENS and 2Hz in the only trial that investigated ALTENS., Conclusion: TENS, administered with a strong, subnoxious intensity at an adequate frequency in the wound area, can significantly reduce analgesic consumption for postoperative pain.