Conceptual complexity of gender and its relevance to pain

Gender Biases in Estimation of Others' Pain

Caregiving and other interpersonal interactions often require accurate perception of others' pain from nonverbal cues, but perceivers may be subject to systematic biases based on gender, race, and other contextual factors. Such biases could contribute to systematic under-recognition and undertreatment of pain. In 2 experiments, we studied the impact of perceived patient sex on lay perceivers' pain estimates and treatment recommendations. In Experiment 1 (N = 50), perceivers viewed facial video clips of female and male patients in chronic shoulder pain and estimated patients' pain intensity. Multi-level linear modeling revealed that perceivers under-estimated female patients' pain compared with male patients, after controlling for patients' self-reported pain and pain facial expressiveness. Experiment 2 (N = 200) replicated these findings, and additionally found that 1) perceivers' pain-related gender stereotypes, specifically beliefs about typical women's vs. men's willingness to express pain, predicted pain estimation biases; and 2) perceivers judged female patients as relatively more likely to benefit from psychotherapy, whereas male patients were judged to benefit more from pain medicine. In both experiments, the gender bias effect size was on average 2.45 points on a 0-100 pain scale. Gender biases in pain estimation may be an obstacle to effective pain care, and experimental approaches to characterizing biases, such as the one we tested here, could inform the development of interventions to reduce such biases. Perspective: This study identifies a bias towards underestimation of pain in female patients, which is related to gender stereotypes. The findings suggest caregivers' or even clinicians' pain stereotypes are a potential target for intervention.

Cross-national trends of chronic back pain in adolescents: results from the HBSC study, 2001-2014

Chronic back pain is a common problem that negatively impacts the wellbeing of many adolescents. Prior research suggests that the prevalence of chronic back pain has increased over the last decades, but research on this issue is scarce, single country-based, and has yielded inconsistent results. This study aimed to examine trends in the prevalence of chronic back pain over time in adolescents aged 11, 13 and 15, using data from the Health Behavior in School-aged Children (HBSC) survey. We conducted a secondary analysis of data from 650,851 adolescents, retrieved from four waves (2001/02, 2005/06, 2009/10 and 2013/14) of HBSC data from 33 countries or regions. The prevalence of back pain was higher (1) in each successive survey over time (18.3% in 2001/02, 19.3% in 2005/06, 20.4% in2009/10 and 21.6% in 2013/14), (2) in girls (21.9%) compared to boys (17.8%), and (3) in older adolescents compared to younger ones (14.5% in 11-year-olds, 19.6% in 13-year-olds and 25.5% in 15-year-olds). The increase in prevalence from 2001/02 to 2013/14 was more marked in older girls compared to younger girls, and in older boys compared to younger boys, and it ranged between 1% for 11-year-old boys and 7% for 15-year-old girls. More resources should be allocated to the prevention and treatment of chronic back pain in adolescents, especially for older girls.

Mouse Anesthesia: The Art and Science

There is an art and science to performing mouse anesthesia, which is a significant component to animal research. Frequently, anesthesia is one vital step of many over the course of a research project spanning weeks, months, or beyond. It is critical to perform anesthesia according to the approved research protocol using appropriately handled and administered pharmaceutical-grade compounds whenever possible. Sufficient documentation of the anesthetic event and procedure should also be performed to meet the legal, ethical, and research reproducibility obligations. However, this regulatory and documentation process may lead to the use of a few possibly oversimplified anesthetic protocols used for mouse procedures and anesthesia. Although a frequently used anesthetic protocol may work perfectly for each mouse anesthetized, sometimes unexpected complications will arise, and quick adjustments to the anesthetic depth and support provided will be required. As an old saying goes, anesthesia is 99% boredom and 1% sheer terror. The purpose of this review article is to discuss the science of mouse anesthesia together with the art of applying these anesthetic techniques to provide readers with the knowledge needed for successful anesthetic procedures. The authors include experiences in mouse inhalant and injectable anesthesia, peri-anesthetic monitoring, specific procedures, and treating common complications. This article utilizes key points for easy access of important messages and authors’ recommendation based on the authors’ clinical experiences.

Attentional Biases Towards Body Expressions of Pain in Men and Women

This study investigated whether there are gender differences in attention to bodily expressions of pain and core emotions. Three experiments are reported using the attentional dot probe task. Images of men and women displaying bodily expressions, including pain, were presented. The task was used to determine whether participants' attention was drawn towards or away from target expressions. Inconsistent evidence was found for an attentional bias towards body expressions, including pain. While biases were affected by gender, patterns varied across the Experiments. Experiment 1, which had a presentation duration of 500 ms, found a relative bias towards the location of male body expressions compared to female expressions. Experiments 2 and 3 varied stimulus exposure times by including both shorter and longer duration conditions (e.g., 100 vs. 500 vs. 1250 ms). In these experiments, a bias towards pain was confirmed. Gender differences were also found, especially in the longer presentation conditions. Expressive body postures captured the attention of women for longer compared to men. These results are discussed in light of their implications for why there are gender differences in attention to pain, and what impact this has on pain behaviour. PERSPECTIVE: We show that men and women might differ in how they direct their attention towards bodily expressions, including pain. These results have relevance to understanding how carers might attend to the pain of others, as well as highlighting the wider role that social-contextual factors have in pain.

Female Gender Is Associated with a Higher Prevalence of Chronic Neck Pain, Chronic Low Back Pain, and Migraine: Results of the Spanish National Health Survey, 2017

OBJECTIVES

To assess the prevalence of chronic neck pain (CNP), chronic low back pain (CLBP), and migraine headache (MH) in the Spanish population and to identify sociodemographic and health-related variables associated with CNP, CLBP, and MH.

DESIGN

Observational study.

SETTING

Spain.

SUBJECTS

A total of 22,511 persons 18 years of age or older (10,304 males and 12,207 females) who participated in the 2017 Spanish National Health Survey.

METHODS

Stratified three-stage sampling was applied. CNP, CLBP, and MH were the dependent variables. The analysis was conducted separately by gender. Sociodemographic features, self-perceived health status, lifestyle habits, comorbidities, and pain features were analyzed by using logistic regression models.

RESULTS

Females reported a higher prevalence of CNP, CLBP, and MH (P < 0.001) than males. For both sexes, anxiety and/or depression and poor self-rated health were associated with a significantly increased prevalence of CNP, CLBP, and MH. For CNP and CLBP, the identified associated factors were older age and limitations to usual activity. For CNP and MH, the most common associated factor was comorbid respiratory disease.

CONCLUSIONS

Our study identified several factors associated with CNP, CLBP, and MH in Spanish female and male adults, with potential implications for health care providers.

A qualitative study of the experience and impact of neuropathic pain in people living with HIV

Painful distal symmetrical polyneuropathy is common in HIV and is associated with reduced quality of life. Research has not explored the experience of neuropathic pain in people with HIV from a person-centred perspective. Therefore, a qualitative interview study was conducted to more deeply understand the experience and impact of neuropathic pain in this population. Semistructured interviews were conducted with 26 people with HIV and peripheral neuropathic pain symptoms. Interviews explored the impact of pain and participants' pain management strategies. Interviews were transcribed verbatim and analysed using thematic analysis. Four themes and 11 subthemes were identified. Theme 1 reflects the complex characterisation of neuropathic pain, including the perceived unusual nature of this pain and diagnostic uncertainty. Theme 2 centred on the interconnected impacts of pain on mood and functioning and includes how pain disrupts relationships and threatens social inclusion. Theme 3 reflects the struggle for pain relief, including participants' attempts to "exhaust all options" and limited success in finding lasting relief. The final theme describes how pain management is complicated by living with HIV; this theme includes the influence of HIV stigma on pain communication and pain as an unwanted reminder of HIV. These data support the relevance of investigating and targeting psychosocial factors to manage neuropathic pain in HIV.

Pain in Women: A Perspective Review on a Relevant Clinical Issue that Deserves Prioritization

Introduction

Gender equity and gender medicine are opportunities not to be missed, and this Expert Group Opinion Paper on pain in women aims to review the treatment of pain conditions mainly affecting women, as well as the fundamental aspects of the different clinical response to drug treatment between the genders, and what can be done for gender-specific rehabilitation.

Methods

Perspective review.

Results

Genotypic and phenotypic differences in pain between the sexes are conditioned by anatomical, physiological, neural, hormonal, psychological, social, and cultural factors, such as the response to pharmacological treatment to control pain. The examination of these factors shows that women are affected by pain diseases more frequently and severely than men and that they report pain more frequently and with a lower pain threshold than men. Some forms of pain are inherently related to gender differences, such as pain related to the genitourinary system. However, other forms of chronic pain are seen more frequently in women than men, such as migraine, rheumatological, and musculoskeletal pain, in particular fibromyalgia.

Discussion

Research is needed into the pathophysiological basis for gender differences in the generation of acute pain and maintenance of chronic pain, including the factors that put women at higher risk for developing chronic pain. In addition, different specialties need to collaborate to develop gender-related diagnostic and therapeutic guidelines, and healthcare professionals need to upskill themselves in the appropriate management of pain using existing diagnostic tools and therapeutic options.

Confirmatory factor analysis of the International Pain Outcome questionnaire in surgery

Supplemental Digital Content is Available in the Text.

The reliability and validity of International Pain Outcome questionnaire Spanish adaptation is confirmed in a large heterogeneous sample. Factor scores can be used as a global outcome analysis tool.

Background:

Choosing perioperative suitable treatments requires reliable and valid outcome measurements. The International Pain Outcome (IPO) questionnaire has been widely used for quality improvement and research purposes within the PAIN-OUT network that has collected more than 550,000 data sets of postoperative patients in 200 hospitals worldwide. Our aim is to confirm psychometric properties of the Spanish version of the IPO questionnaire and its invariance by pain predictors.

Method:

Sample included 4014 participants within a large age range, who underwent different surgical procedures. Confirmatory factor analysis (CFA) assessed internal structure, considering invariance by sex, age, procedure, smoking, obesity, affective disorder, and chronic pain. Incremental predictive validity of factor scores on question would have liked more pain treatment and opioid requirement was also estimated with logistic binary regression.

Results:

Confirmatory factor analysis verified original structure in 3 factors measuring pain intensity and interference (F1), adverse effects (F2), and perceptions of care (F3), with good internal consistency. Multigroup CFA analysis confirmed invariance by assessed pain predictors. Good incremental predictive capacity to identify would have liked more pain treatment was achieved.

Conclusion:

Our study confirms the factor structure, supports reliability, and adds some evidence of convergent validity of the Spanish adaptation of the IPO questionnaire. The sum of scores in its main factors serves a global outcome analysis tool. Low scores in F1 and F2 with high scores in F3 would indicate optimal quality of care.

Sexual dimorphism in the contribution of neuroendocrine stress axes to oxaliplatin-induced painful peripheral neuropathy

ABSTRACT

Although clinical studies support the suggestion that stress is a risk factor for painful chemotherapy-induced peripheral neuropathy (CIPN), there is little scientific validation to support this link. Here, we evaluated the impact of stress on CIPN induced by oxaliplatin, and its underlying mechanisms, in male and female rats. A single dose of oxaliplatin produced mechanical hyperalgesia of similar magnitude in both sexes, still present at similar magnitude in both sexes, on day 28. Adrenalectomy mitigated oxaliplatin-induced hyperalgesia, in both sexes. To confirm the role of neuroendocrine stress axes in CIPN, intrathecal administration of antisense oligodeoxynucleotide targeting β₂-adrenergic receptor mRNA both prevented and reversed oxaliplatin-induced hyperalgesia, only in males. By contrast, glucocorticoid receptor antisense oligodeoxynucleotide prevented and reversed oxaliplatin-induced hyperalgesia in both sexes. Unpredictable sound stress enhanced CIPN, in both sexes. The administration of stress hormones, epinephrine, corticosterone, and their combination, at stress levels, mimicked the effects of sound stress on CIPN, in males. In females, only corticosterone mimicked the effect of sound stress. Also, a risk factor for CIPN, early-life stress, was evaluated by producing both stress-sensitive (produced by neonatal limited bedding) and stress-resilient (produced by neonatal handling) phenotypes in adults. Although neonatal limited bedding significantly enhanced CIPN only in female adults, neonatal handling significantly attenuated CIPN, in both sexes. Our study demonstrates a sexually dimorphic role of the 2 major neuroendocrine stress axes in oxaliplatin-induced neuropathic pain.

Allodynia by Splenocytes From Mice With Acid-Induced Fibromyalgia-Like Generalized Pain and Its Sexual Dimorphic Regulation by Brain Microglia

Fibromyalgia (FM), a disease of unknown etiology characterized by chronic generalized pain, is partly recapitulated in an animal model induced by repeated acid saline injections into the gastrocnemius muscle. Here, we attempted to investigate the sex difference in pain hypersensitivity (mechanical allodynia and hypersensitivity to electrical stimulation) in the repeated acid saline-induced FM-like generalized pain (AcGP) model. The first unilateral acid injection into gastrocnemius muscle at day 0/D0 and second injection at D5 (post day 0, P0) induced transient and long-lasting mechanical allodynia, respectively, on both sides of male and female mice. The pretreatment with gonadectomy did not affect the first injection-induced allodynia in both sexes, but gradually reversed the second injection-induced allodynia in male but not female mice. Moreover, the AcGP in male mice was abolished by intracerebroventricular minocycline treatments during D4–P4 or P5–P11, but not by early treatments during D0–D5 in male but not female mice, suggesting that brain microglia are required for AcGP in late-onset and sex-dependent manners. We also found that the intravenous treatments of splenocytes derived from male but not female mice treated with AcGP caused allodynia in naive mice. In addition, the purified CD4⁺ T cells derived from splenocytes of acid-treated male mice retained the ability to cause allodynia in naive mice. These findings suggest that FM-like AcGP has multiple sexual dimorphic mechanisms.

Risk factors and events in the adult intensive care unit associated with pain as self-reported at the end of the intensive care unit stay

Background

The short-term and long-term consequences of the most frequent painful procedures performed in the ICU are unclear. This study aimed to identify the risk factors associated with pain-related discomfort perceived by critically ill patients during the whole ICU stay as self-reported by patients at the end of their ICU stay.

Methods

The study involved 34 ICUs. Adult patients who survived an ICU stay of 3 calendar days or more were eligible for inclusion. Discomforts, including the pain-related discomfort, were assessed using the French 18-item questionnaire on discomfort in ICU patients, the “Inconforts des Patients de REAnimation” (IPREA). Patients scored each item from 0 (minimal discomfort) to 10 (maximal discomfort). Associations between patient characteristics at ICU admission, life support therapies and main potentially painful procedures performed during the ICU stay and pain-related discomfort scores assessed at the end of the ICU stay were analyzed.

Results

Patients with complete IPREA questionnaires (n = 2130) were included. The median pain-related discomfort score was 3 (IQR 0–5). From the univariate analysis, pain-related discomfort scores were negatively correlated with age and positively correlated with ICU stay duration; surgical patients reported significant higher pain-related discomfort scores than medical patients; chest drain insertion, chest drain removal, use of bladder catheter, central venous catheter (CVC) insertion, complex dressing change, and intra-hospital transport were associated with pain-related discomfort scores. From the multivariate analyses using generalized estimating equations models, only age, chest drain removal, use of a bladder catheter, CVC insertion, and intra-hospital transport were the main risk factors associated with pain-related discomfort scores.

Conclusion

Patients who underwent chest drain removal, bladder catheter, CVC insertion, and intra-hospital transport during their ICU stay reported higher pain-related discomfort scores (with respect to the whole ICU stay and assessed at the end of their ICU stay) than patients who did not experience these events. This study may pave the way for further targeted studies aiming at investigating a causal link between these common procedures in the ICU and adult critically ill patients’ perceptions of their ICU stay regarding recalled pain.

Trial Registration: Clinicaltrials.gov Identifier NCT02442934, retrospectively registered on May 13, 2015

The Relationship Between Education and Pain Among Adults Aged 30-49 in the United States

Pain is a major health problem among U.S. adults. Surprisingly little, however, is known about educational disparities in pain, especially among the nonelderly. In this study, we analyze disparities in pain across levels of educational attainment. Using data from the 2010 to 2017 National Health Interview Survey among adults aged 30 to 49 (N = 74,051), we estimate logistic regression models of pain prevalence using a dichotomous summary pain index and its 5 constituent pain sites (low back, joint, neck, headache/migraine, and facial/jaw). We find a significant and steep pain gradient: greater levels of educational attainment are associated with less pain, with 2 important exceptions. First, adults with a high-school equivalency diploma (GED) and those with "some college" have significantly higher pain levels than high school graduates despite having an equivalent or higher attainment, respectively. Second, the education-pain gradient is absent for Hispanic adults. After taking into account important covariates including employment, economic resources, health behaviors, physical health conditions, and psychological wellbeing, educational disparities in pain are no longer statistically significant except for the GED and "some college" categories, which still show significantly higher pain levels than high school graduates. We thus document the overall education-pain gradient in most younger U.S. adult populations, and identify groups where pain is higher than expected (certain educational categories) or lower than expected (eg, less-educated Hispanics). Understanding the causes of these anomalous findings could clarify factors shaping pain prevalence and disparities therein. PERSPECTIVE: Over 50% of U.S. adults age 30 to 49 report pain. Overall, more educated Americans report substantially less pain than the less educated. However, adults with a GED and "some college" report more pain than other groups. Understanding the causes could help illuminate the mechanisms through which social factors influence pain.

Molecular Mechanisms of Sex-Related Differences in Arthritis and Associated Pain

Clinical conditions leading to chronic pain show important sex-related differences in the prevalence, severity, and degree of functional disability. Decades of epidemiological and clinical studies have demonstrated that women are more sensitive to pain than men. Arthritis, including rheumatoid arthritis (RA) and osteoarthritis (OA), is much more prevalent in females and accounts for the majority of pain arising from musculoskeletal conditions. It is therefore important to understand the mechanisms governing sex-dependent differences in chronic pain, including arthritis pain. However, research into the mechanisms underlying the sex-related differences in arthritis-induced pain is still in its infancy due to the bias in biomedical research performed largely in male subjects and animals. In this review, we discuss current advances in both clinical and preclinical research regarding sex-related differences in the development or severity of arthritis and associated pain. In addition, sex-related differences in biological and molecular mechanisms underlying the pathogenesis of arthritis pain, elucidated based on clinical and preclinical findings, are reviewed.

Gender and palliative care: a call to arms

There has been a systematic and largely unconscious neglect of gender in palliative care research, practice and policy. This is despite significant, although previously uncollated, evidence that gender influences almost all aspects of end-of-life preferences, experiences and care. The social situations of women, transgender people and men often differ from one another while also intersecting in complex ways with sex differences rooted in biology. If palliative care is to meet its aspiration of providing universal benefit, it urgently needs to address a range of gender inequalities currently (re)produced at the level of the laboratory all the way through to government departments. In this call to arms, we spotlight specific instances where gender inequalities have been documented, for example, regarding end-of-life caregiving, end-of-life intervention and palliative care access and benefit. We highlight how gender inequalities intersect with other social determinants of health including ethnicity and economic status to exacerbate situations of marginality. We conclude by offering some practical steps that can be taken to support the discipline to adopt a more critical gender lens to support more equitable research, policy and practice.

The gender context of pain

Pain is a major source of global suffering, with women bearing the greatest burden. Alongside biology, psychological and social factors, including gender, help explain these differences. However, there has been no direct attempt to develop a unified social psychological model of men and women's pain. By drawing on approaches to both gender and pain, a gender context model of pain is presented. It proposes that pain is partly influenced by the gender context in which it occurs, which operates at both individual and interpersonal levels. The model is used to structure an appraisal of the existing evidence around gender and pain, and explore whether the model helps explain why such variation occurs. It is argued that despite evidence for an association between gender and pain, there are empirical gaps that need to be addressed. Implications and directions for future investigations into sex, gender and pain are considered.

Is There an Association between Diabetes and Neck and Back Pain? Results of a Case-Control Study

We aimed to assess if subjects with diabetes exhibit higher prevalence of chronic back pain than age-sex-province of residence-matched non-diabetic controls. We also aimed to identify predictors for chronic neck pain (CNP) or chronic low back pain (CLBP) among subjects with diabetes. A case control study was conducted using data obtained from the Spanish National Health Survey 2017. Multivariable conditional and unconditional logistic regression models were constructed. A total of 2095 diabetes sufferers and 2095 non-diabetic matched controls were analyzed. The prevalence of CNP and CLBP was 27.3% and 34.8%, respectively, in diabetes sufferers and 22.1% and 29.0% in non-diabetes controls (both, p < 0.001). After multivariable analysis, the ORs showed significantly higher adjusted risk of CNP (OR 1.34; 95% CI 1.19–1.51) and CLBP (OR 1.19, 95% CI 1.09–1.31) in diabetes cases. Diabetes sufferers with CNP or CLBP showed higher use of pain medication and higher prevalence of migraine/frequent headache than controls. Female sex, worse self-rated health and use of pain medication were predictors for CNP and CLBP in subjects with diabetes. CNP and CLBP are significantly more prevalent in diabetes sufferers than in controls. Current results can help to design better preventive and educational strategies for these highly prevalent and burdensome pains among diabetic patients.

Validity of Algorithms for Identification of Individuals Suffering from Chronic Noncancer Pain in Administrative Databases: A Systematic Review

BACKGROUND

Secondary analysis of health administrative databases is indispensable to enriching our understanding of health trajectories, health care utilization, and real-world risks and benefits of drugs among large populations.

OBJECTIVES

This systematic review aimed at assessing evidence about the validity of algorithms for the identification of individuals suffering from nonarthritic chronic noncancer pain (CNCP) in administrative databases.

METHODS

Studies reporting measures of diagnostic accuracy of such algorithms and published in English or French were searched in the Medline, Embase, CINAHL, AgeLine, PsycINFO, and Abstracts in Social Gerontology electronic databases without any dates of coverage restrictions up to March 1, 2018. Reference lists of included studies were also screened for additional publications.

RESULTS

Only six studies focused on commonly studied CNCP conditions and were included in the review. Some algorithms showed a ≥60% combination of sensitivity and specificity values (back pain disorders in general, fibromyalgia, low back pain, migraine, neck/back problems studied together). Only algorithms designed to identify fibromyalgia cases reached a ≥80% combination (without replication of findings in other studies/databases).

CONCLUSIONS

In summary, the present investigation informs us about the limited amount of literature available to guide and support the use of administrative databases as valid sources of data for research on CNCP. Considering the added value of such data sources, the important research gaps identified in this innovative review provide important directions for future research. The review protocol was registered with PROSPERO (CRD42018086402).

Sex differences in the role of atypical PKC within the basolateral nucleus of the amygdala in a mouse hyperalgesic priming model

Though sex differences in chronic pain have been consistently described in the literature, their underlying neural mechanisms are poorly understood. Previous work in humans has demonstrated that men and women differentially invoke distinct brain regions and circuits in coping with subjective pain unpleasantness. The goal of the present work was to elucidate the molecular mechanisms in the basolateral nucleus of the amygdala (BLA) that modulate hyperalgesic priming, a pain plasticity model, in males and females. We used plantar incision as the first, priming stimulus and prostaglandin E₂ (PGE₂) as the second stimulus. We sought to assess whether hyperalgesic priming can be prevented or reversed by pharmacologically manipulating molecular targets in the BLA of male or female mice. We found that administering ZIP, a cell-permeable inhibitor of aPKC, into the BLA attenuated aspects of hyperalgesic priming induced by plantar incision in males and females. However, incision only upregulated PKCζ/PKMζ immunoreactivity in the BLA of male mice, and deficits in hyperalgesic priming were seen only when we restricted our analysis to male Prkcz^-/- mice. On the other hand, intra-BLA microinjections of pep2m, a peptide that interferes with the trafficking and function of GluA2-containing AMPA receptors, a downstream target of aPKC, reduced mechanical hypersensitivity after plantar incision and disrupted the development of hyperalgesic priming in both male and female mice. In addition, pep2m treatment reduced facial grimacing and restored aberrant behavioral responses in the sucrose splash test in male and female primed mice. Immunofluorescence results demonstrated upregulation of GluA2 expression in the BLA of male and female primed mice, consistent with pep2m findings. We conclude that, in a model of incision-induced hyperalgesic priming, PKCζ/PKMζ in the BLA is critical for the development of hyperalgesic priming in males, while GluA2 in the BLA is crucial for the expression of both reflexive and affective pain-related behaviors in both male and female mice in this model. Our findings add to a growing body of evidence of sex differences in molecular pain mechanisms in the brain.

A myelin basic protein fragment induces sexually dimorphic transcriptome signatures of neuropathic pain in mice

In the peripheral nerve, mechanosensitive axons are insulated by myelin, a multilamellar membrane formed by Schwann cells. Here, we offer first evidence that a myelin degradation product induces mechanical hypersensitivity and global transcriptomics changes in a sex-specific manner. Focusing on downstream signaling events of the functionally active 84-104 myelin basic protein (MBP(84-104)) fragment released after nerve injury, we demonstrate that exposing the sciatic nerve to MBP(84-104) via endoneurial injection produces robust mechanical hypersensitivity in female, but not in male, mice. RNA-seq and systems biology analysis revealed a striking sexual dimorphism in molecular signatures of the dorsal root ganglia (DRG) and spinal cord response, not observed at the nerve injection site. Mechanistically, intra-sciatic MBP(84-104) induced phospholipase C (PLC)-driven (females) and phosphoinositide 3-kinase-driven (males) phospholipid metabolism (tier 1). PLC/inositol trisphosphate receptor (IP3R) and estrogen receptor co-regulation in spinal cord yielded Ca²⁺-dependent nociceptive signaling induction in females that was suppressed in males (tier 2). IP3R inactivation by intrathecal xestospongin C attenuated the female-specific hypersensitivity induced by MBP(84-104). According to sustained sensitization in tiers 1 and 2, T cell-related signaling spreads to the DRG and spinal cord in females, but remains localized to the sciatic nerve in males (tier 3). These results are consistent with our previous finding that MBP(84-104)-induced pain is T cell-dependent. In summary, an autoantigenic peptide endogenously released in nerve injury triggers multisite, sex-specific transcriptome changes, leading to neuropathic pain only in female mice. MBP(84-104) acts through sustained co-activation of metabolic, estrogen receptor-mediated nociceptive, and autoimmune signaling programs.

Cellular Circuits in the Brain and Their Modulation in Acute and Chronic Pain

Chronic, pathological pain remains a global health problem and a challenge to basic and clinical sciences. A major obstacle to preventing, treating, or reverting chronic pain has been that the nature of neural circuits underlying the diverse components of the complex, multidimensional experience of pain is not well understood. Moreover, chronic pain involves diverse maladaptive plasticity processes, which have not been decoded mechanistically in terms of involvement of specific circuits and cause-effect relationships. This review aims to discuss recent advances in our understanding of circuit connectivity in the mammalian brain at the level of regional contributions and specific cell types in acute and chronic pain. A major focus is placed on functional dissection of sub-neocortical brain circuits using optogenetics, chemogenetics, and imaging technological tools in rodent models with a view towards decoding sensory, affective, and motivational-cognitive dimensions of pain. The review summarizes recent breakthroughs and insights on structure-function properties in nociceptive circuits and higher order sub-neocortical modulatory circuits involved in aversion, learning, reward, and mood and their modulation by endogenous GABAergic inhibition, noradrenergic, cholinergic, dopaminergic, serotonergic, and peptidergic pathways. The knowledge of neural circuits and their dynamic regulation via functional and structural plasticity will be beneficial towards designing and improving targeted therapies.

Current perspectives on sex differences in tension-type headache

INTRODUCTION

Clinical and experimental evidence supports the presence of several gender differences in the pain experience.

AREAS COVERED

The current paper discusses biological, psychological, emotional, and social differences according to gender and their relevance to TTH. Gender differences have also been observed in men and women with tension-type headache and they should be considered by clinicians managing this condition. It appears that multimodal treatment approaches lead to better outcomes in people with tension-type headache; however, management of tension-type headache should consider these potential gender differences. Different studies have observed the presence of complex interactions between tension-type headache, emotional stress, sleep, and burden and that these interactions are different between men and women.

EXPERT OPINION

Based on current results, the authors hypothesize that treatment of men with tension-type headache should focus on the improvement of sleep quality and the level of depression whereas treatment of women with TTH should focus on nociceptive mechanisms and emotional/stressful factors. Future trials should investigate the proposed hypotheses.

Comparing the experience of individuals with primary and secondary lymphoedema: A qualitative study

BACKGROUND

Lymphoedema is a chronic condition that has significant detrimental impact on patients' quality of life. Secondary lymphoedema often results from anti-tumour treatment, in contrast to primary lymphoedema which is the result of genetic abnormalities that leads to an abnormal development of the lymphatic system.

OBJECTIVE

To describe and compare the experience of individuals with primary and secondary lymphoedema.

METHODS

A total of 19 patients (mean ± standard deviation age: 56.7 ± 16.2 years), 8 with primary and 11 with secondary lymphoedema, participated in this qualitative phenomenological study. Purposeful sampling method was applied. We recruited participants from specialised lymphoedema units of two physical therapy clinics and the Lymphoedema Patient Association in Spain. Data collection methods included unstructured and semi-structured interviews. An inductive thematic analysis was used.

RESULTS

The findings suggest differences between the experience of living with primary or secondary lymphoedema. Also, those with lower extremity lymphoedema have more pain, fatigue, and functional limitations. Three primary themes emerged: "Emotional challenge", "Adapting your life to a new situation," and "lymphoedema management".

CONCLUSIONS

The experience of living with lymphoedema involves aspects of fear, suffering, coping, and management of the disease and differs between secondary and primary causes. However, it seems to be more dependent on its location than its cause.

Qualitative sex differences in pain processing: emerging evidence of a biased literature

Although most patients with chronic pain are women, the preclinical literature regarding pain processing and the pathophysiology of chronic pain has historically been derived overwhelmingly from the study of male rodents. This Review describes how the recent adoption by a number of funding agencies of policies mandating the incorporation of sex as a biological variable into preclinical research has correlated with an increase in the number of studies investigating sex differences in pain and analgesia. Trends in the field are analysed, with a focus on newly published findings of qualitative sex differences: that is, those findings that are suggestive of differential processing mechanisms in each sex. It is becoming increasingly clear that robust differences exist in the genetic, molecular, cellular and systems-level mechanisms of acute and chronic pain processing in male and female rodents and humans.

Conducting gender-based analysis of existing databases when self-reported gender data are unavailable: the GENDER Index in a working population

OBJECTIVES

Growing attention has been given to considering sex and gender in health research. However, this remains a challenge in the context of retrospective studies where self-reported gender measures are often unavailable. This study aimed to create and validate a composite gender index using data from the Canadian Community Health Survey (CCHS).

METHODS

According to scientific literature and expert opinion, the GENDER Index was built using several variables available in the CCHS and deemed to be gender-related (e.g., occupation, receiving child support, number of working hours). Among workers aged 18-50 years who had no missing data for our variables of interest (n = 29,470 participants), propensity scores were derived from a logistic regression model that included gender-related variables as covariates and where biological sex served as the dependent variable. Construct validity of propensity scores (GENDER Index scores) were then examined.

RESULTS

When looking at the distribution of the GENDER Index scores in males and females, they appeared related but partly independent. Differences in the proportion of females appeared between groups categorized according to the GENDER Index scores tertiles (p < 0.0001). Construct validity was also examined through associations between the GENDER Index scores and gender-related variables identified a priori such as choosing/avoiding certain foods because of weight concerns (p < 0.0001), caring for children as the most important thing contributing to stress (p = 0.0309), and ability to handle unexpected/difficult problems (p = 0.0375).

CONCLUSION

The GENDER Index could be useful to enhance the capacity of researchers using CCHS data to conduct gender-based analysis among populations of workers.

Consultation prevalence among children, adolescents and young adults with pain conditions: A description of age- and gender differences

BACKGROUND

Pain is a common complaint presented in healthcare, but most epidemiological pain research has focused either on single pain conditions or on the adult population. The aim of this study was to investigate the 2017 consultation prevalence of a wide range of pain conditions in the general population of young people.

METHODS

We used the Skåne Healthcare Register, covering prospectively collected data on all healthcare delivered (primary and secondary care) to the population in the region of Skåne, southern Sweden (population 2017 n = 1,344,689). For individuals aged 1-24 in 2017 (n = 373,178), we calculated the consultation prevalence, stratified by sex and age, and the standardised morbidity ratio (SMR) to assess overall healthcare consultation.

RESULTS

A total of 58,981 (15.8%) individuals consulted at least once for any of the predefined pain conditions. Of these, 13.5% (n = 7,996) consulted four or more times for pain. Abdominal pain, joint pain/myalgia, headache and back/neck pain were the most common complaints. Overall, females had higher consultation prevalence than males: 17.6% versus 14.1% (p < .0001). SMR was 1.82 (95% CI = 1.74-1.87) for females with pain and 1.51 (95% CI = 1.42-1.56) for males with pain. Consultation prevalence increased with age, but this pattern varied between sex and pain condition.

CONCLUSIONS

Among individuals under the age of 25, a significant proportion consult for pain already in early ages, and they also have high healthcare consultation rates for conditions other than pain. The even higher consultation rates among young females need additional attention, both in the clinic and in research.

SIGNIFICANCE

We present comprehensive 1-year healthcare consultation prevalence data covering all levels of care. A significant proportion of children, adolescents and young adults consult for different pain conditions at multiple occasions warranting greater clinical awareness.

A Review of Strain and Sex Differences in Response to Pain and Analgesia in Mice

Pain and its alleviation are currently a highly studied issue in human health. Research on pain and response to analgesia has evolved to include the effects of genetics, heritability, and sex as important components in both humans and animals. The laboratory mouse is the major animal studied in the field of pain and analgesia. Studying the inbred mouse to understand how genetic heritable traits and/or sex influence pain and analgesia has added valuable information to the complex nature of pain as a human disease. In the context of biomedical research, identifying pain and ensuring its control through analgesia in research animals remains one of the hallmark responsibilities of the research community. Advancements in both human and mouse genomic research shed light not only on the need to understand how both strain and sex affect the mouse pain response but also on how these research achievements can be used to improve the humane use of all research animal species. A better understanding of how strain and sex affect the response to pain may allow researchers to improve study design and thereby the reproducibility of animal research studies. The need to use both sexes, along with an improved understanding of how genetic heritability affects nociception and analgesic sensitivity, remains a key priority for pain researchers working with mice. This review summarizes the current literature on how strain and sex alter the response to pain and analgesia in the modern research mouse, and highlights the importance of both strain and sex selection in pain research.

Psychological factors are associated with local and generalized pressure pain hypersensitivity, pain intensity, and function in people with chronic shoulder pain: A cross-sectional study

OBJECTIVES

To explore the association between psychological factors and shoulder pain intensity, function, as well as local and generalized pressure pain hypersensitivity.

DESIGN

a cross-sectional study.

METHODS

90 participants with chronic shoulder pain were included. Pressure pain thresholds determined the presence of pain hypersensitivity. Pain intensity, function, pain self-efficacy, emotional distress, and pain catastrophizing were also assessed. Analyses were adjusted for gender and age.

RESULTS

The diagnosis of depression (yes/no answer) was associated with both greater local (standardized β = -0.19[95%CI -0.37 to -0.00]) and generalized (standardized β = -0.20[95%CI -0.39 to -0.01]) pressure pain hypersensitivity. Greater pain self-efficacy was associated with lower local pressure pain hypersensitivity (standardized β = 0.19[95%CI 0.04 to 0.38]). The standardized beta coefficient for the diagnosis of depression indicated that this variable showed the strongest association with pressure pain hypersensitivity. Additionally, greater pain self-efficacy was associated with lower pain intensity (standardized β = -0.34[95%CI -0.51 to -0.17]) and better function (standardized β = -0.47[95%CI -0.63 to -0.30]). Greater pain catastrophizing was associated with more pain intensity (standardized β = 0.35[95%CI 0.18 to 0.52]) and worse function (standardized β = 0.26[95%CI 0.10 to 0.43]). The standardized beta coefficients for pain catastrophizing and pain self-efficacy indicated that both variables showed the strongest association with shoulder pain intensity and function, respectively CONCLUSION: Psychological factors were associated with local and generalized pressure pain hypersensitivity, pain intensity, and function in people with chronic shoulder pain.

"I can't have it; I am a man. A young man!" - men, fibromyalgia and masculinity in a Nordic context

Purpose: Research shows that gender has a substantial impact on the health behaviour such as expression of physical symptoms like persistent pains and aches. However, there is yet little knowledge about the gendered aspect of pain by men who suffer from typical female diseases like fibromyalgia. The purpose of the study was to elucidate the interplay between illness and gender by exploring life-stories of men who suffer from fibromyalgia. Methods: The data were collected through life-story interviews of eight men suffering from fibromyalgia. A narrative methodology for analysis was applied to explore the storytelling and the linguistic and performative aspects of the life-stories. Results: The masculine identity of the participants was re-negotiated by comparisons to other men and life before symptom onset, and by discussing expectations and beliefs of how men should act in contemporary societies. The transition from experiencing a strong, active and reliable body to experiencing a painful, vulnerable and helpless body was perceived as fundamental. Conclusions: Self-management and rehabilitation of fibromyalgia it is not only about learning to manage the symptoms but also about the struggle to find coherence in life through re-constructing gender identity that is acceptable both for the individual and for the community.

Exploring the relationship between male norm beliefs, pain-related beliefs and behaviours: An online questionnaire study

BACKGROUND

Gender beliefs help explain the variation found in pain among men and women. Gender norms and expectations are thought to affect how men and women report and express pain. However, less is known about how such beliefs are related to pain outside of laboratory settings. The aim of this study was therefore to consider the relationship between beliefs in male role norms, pain and pain behaviours in men and women.

METHODS

An online questionnaire study was conducted. A total of 468 adults (352 women), with or without pain, completed a series of self-report measures relating to beliefs about pain and male role norms, as well as pain and general health behaviours.

RESULTS

An experience of pain was associated with lower beliefs in traditional male norms. Endorsing stereotypical male norms was related to increased stigma associated with seeking professional help for pain in both men and women, but to a lesser extent associated with general health behaviours. There also seemed to be gender-based beliefs associated with the expression of pain.

CONCLUSIONS

Together these findings suggest that beliefs in gender (male) norms are relevant to pain, and that there is utility in exploring the variation in pain beyond binary male-female categories.