Gender differences in temporal summation of mechanically evoked pain

The Dose-Response Relationship between Opioid Agonist Therapy and Alterations in Pain Pathways in Patients with Opioid Use Disorders: A Cross-Sectional Study

INTRODUCTION

The administration of opioids can be followed by enduring neuroplastic changes in the peripheral and central nervous systems. This remodeling can lead to opioid-induced hyperalgesia, causing an increased sensitivity to painful stimuli. The description of opioid-induced changes in the somatosensory system has seldom been described in the setting of opioid agonist therapy in the treatment of opioid use disorders, and the few existing reports provide no guidance with respect to the effect of varied doses or substances.

OBJECTIVE

The aim of the present study was to assess alterations of pain pathways among patients receiving opioid agonist therapy and to elucidate the dose-response relationship.

METHODS

This study was planned as cross-sectional in an outpatient clinic in Graz, Austria. Patients receiving opioid agonist therapy for opioid use disorders (including methadone, levomethadone, buprenorphine, and extended-release morphine) were asked to fill out a questionnaire, including the central sensitization inventory. A battery of somatosensory system assessments was then performed.

RESULTS

A total of 120 patients participated (85 men/35 women). The mean oral morphine milligram equivalent (MME) was 694 ± 249 mg/day. Our study found significant alterations in pain perception, conditioned pain modulation, and wind-up. We demonstrated a moderate dose-response relationship between high-dose opioids and markers of central sensitization.

CONCLUSION

The present trial demonstrates the clear effects of opioid agonist therapy on the somatosensory system. Both central sensitization and descending pain modulation are negatively affected by high doses of opioids and our data elucidate a moderate dose-response relationship for these phenomena.

Impact of different CRPS phenotypes and diagnostic criteria on quantitative sensory testing outcomes: systematic review and meta-analysis

OBJECTIVES

This review and meta-analysis evaluated the impact of diagnostic criteria and clinical phenotypes on quantitative sensory testing (QST) outcomes in patients with complex regional pain syndrome (CRPS).

METHODS

Eight databases were searched based on a previously published protocol. Forty studies comparing QST outcomes between CRPS-I vs II, warm vs cold CRPS, upper vs lower limb CRPS, males vs females, or using Budapest vs older IASP criteria were included.

RESULTS

Studies investigating QST differences between CRPS-I vs II (n = 4), between males vs females (n = 2), and between upper and lower limb CRPS (n = 2) showed no significant differences. Four studies compared QST outcomes in warm vs cold CRPS, showing heat hyperalgesia in warm CRPS, with thermal and mechanical sensory loss in cold CRPS. Although CRPS diagnosed using the Budapest criteria (24 studies) vs 1994 IASP criteria (13 studies) showed similar sensory profiles, there was significant heterogeneity and low quality of evidence in the latter.

CONCLUSIONS

Based on the findings of this review, classifying CRPS according to presence or absence of nerve lesion into CRPS-I and II, location (upper or lower limb) or according to sex might not be clinically relevant as all appear to have comparable sensory profiles that might suggest similar underlying mechanisms. In contrast, warm vs cold phenotypes exhibited clear differences in their associated QST sensory profiles. To the extent that differences in underlying mechanisms might lead to differential treatment responsiveness, it appears unlikely that CRPS-I vs II, CRPS location, or patient sex would prove useful in guiding clinical management.

The effect of unpredictability on the perception of pain: a systematic review and meta-analysis

ABSTRACT

Despite being widely assumed, the worsening impact of unpredictability on pain perception remains unclear because of conflicting empirical evidence, and a lack of systematic integration of past research findings. To fill this gap, we conducted a systematic review and meta-analysis focusing on the effect of unpredictability on pain perception. We also conducted meta-regression analyses to examine the moderating effect of several moderators associated with pain and unpredictability: stimulus duration, calibrated stimulus pain intensity, pain intensity expectation, controllability, anticipation delay, state and trait negative affectivity, sex/gender and age of the participants, type of unpredictability (intensity, onset, duration, location), and method of pain induction (thermal, electrical, mechanical pressure, mechanical distention). We included 73 experimental studies with adult volunteers manipulating the (un)predictability of painful stimuli and measuring perceived pain intensity and pain unpleasantness in predictable and unpredictable contexts. Because there are insufficient studies with patients, we focused on healthy volunteers. Our results did not reveal any effect of unpredictability on pain perception. However, several significant moderators were found, ie, targeted stimulus pain intensity, expected pain intensity, and state negative affectivity. Trait negative affectivity and uncontrollability showed no significant effect, presumably because of the low number of included studies. Thus, further investigation is necessary to clearly determine their role in unpredictable pain perception.

Painful Cutaneous Laser Stimulation for Temporal Summation of Pain Assessment

Variability in pain sensitivity arises not only from the differences in peripheral sensory receptors but also from the differences in central nervous system (CNS) pain inhibition and facilitation mechanisms. Temporal summation of pain (TSP) is an experimental protocol commonly used in human studies of pain facilitation but is susceptible to confounding when elicited with the skin-contact thermode, which adds the responses of touch-related Aβ low-threshold mechanoreceptors to nociceptive receptors. In the present study, we evaluate an alternative method involving the use of a contactless cutaneous laser for TSP assessment. We show that repetitive laser stimulations with a one second inter-stimulus interval evoked reliable TSP responses in a significant proportion of healthy subjects (N = 36). Female subjects (N = 18) reported greater TSP responses than male subjects confirming earlier studies of sex differences in central nociceptive excitability. Furthermore, repetitive laser stimulations during TSP induction elicited increased time-frequency electroencephalography (EEG) responses. The present study demonstrates that repetitive laser stimulation may be an alternative to skin-contact methods for TSP assessment in patients and healthy controls. PERSPECTIVE: Temporal summation of pain (TSP) is an experimental protocol commonly used in human studies of pain facilitation. We show that contactless cutaneous laser stimulation is a reliable alternative to the skin contact approaches during TSP assessment.

Body Mass Index and Its Influence on Chronic Low Back Pain in the Spanish Population: A Secondary Analysis from the European Health Survey (2020)

Risk factors such as obesity and a sedentary lifestyle contribute to the development of chronic low back pain.

PURPOSE

To describe how body mass index (BMI) influences the prevalence of chronic low back pain in the general Spanish population and assess this influence given other factors as sex, age, physical occupational demands, and recreational physical activity.

METHODS

An analytical cross-sectional design was performed based on secondary data from the European Health Survey in Spain (2020). Data on age, gender, physical occupational demands, physical activity, BMI, and presence of chronic low back pain were extracted.

RESULTS

A total of 19,716 (52.2% women) subjects with a median age of 53 years old were analyzed. Of these, 18.3% had chronic low back pain, 39% were overweight, and 16.1% were obese. The adjusted generalized linear model showed that being obese increased the odds of chronic low back pain by 1.719 times (p < 0.001). Being a woman increased the odds by 1.683 times (p < 0.001). Performing occupational tasks requiring high physical demands increased the odds by 1.403 times (p < 0.001). Performing physical activity in leisure time several times a week decreased the odds by 0.598 times (p < 0.001). For every additional year of age, the odds of chronic low back pain increased by 3.3% (p < 0.001).

CONCLUSIONS

Obesity is related with the presence of chronic low back pain in the general Spanish population. This association persists, being the more relevant factor, after adjusting the association of BMI and chronic low back pain with other factors such as sex, age, physical occupational demands, and recreational physical activity.

Machine learning analysis predicts a person's sex based on mechanical but not thermal pain thresholds

Sex differences in pain perception have been extensively studied, but precision medicine applications such as sex-specific pain pharmacology have barely progressed beyond proof-of-concept. A data set of pain thresholds to mechanical (blunt and punctate pressure) and thermal (heat and cold) stimuli applied to non-sensitized and sensitized (capsaicin, menthol) forearm skin of 69 male and 56 female healthy volunteers was analyzed for data structures contingent with the prior sex structure using unsupervised and supervised approaches. A working hypothesis that the relevance of sex differences could be approached via reversibility of the association, i.e., sex should be identifiable from pain thresholds, was verified with trained machine learning algorithms that could infer a person's sex in a 20% validation sample not seen to the algorithms during training, with balanced accuracy of up to 79%. This was only possible with thresholds for mechanical stimuli, but not for thermal stimuli or sensitization responses, which were not sufficient to train an algorithm that could assign sex better than by guessing or when trained with nonsense (permuted) information. This enabled the translation to the molecular level of nociceptive targets that convert mechanical but not thermal information into signals interpreted as pain, which could eventually be used for pharmacological precision medicine approaches to pain. By exploiting a key feature of machine learning, which allows for the recognition of data structures and the reduction of information to the minimum relevant, experimental human pain data could be characterized in a way that incorporates "non" logic that could be translated directly to the molecular pharmacological level, pointing toward sex-specific precision medicine for pain.

The Effect of Palmitoylethanolamide on Pain Intensity, Central and Peripheral Sensitization, and Pain Modulation in Healthy Volunteers-A Randomized, Double-Blinded, Placebo-Controlled Crossover Trial

Palmitoylethanolamide (PEA) is marketed as a “dietary food for special medical purposes”. Its broad-spectrum analgesic, anti-inflammatory, and neuroprotective effects make PEA an interesting substance in pain management. However, the underlying analgetic mechanisms have not yet been investigated in humans. The aim of our study is to provide a deeper understanding of the involved mechanisms, which is essential for differentiating therapeutic approaches and the establishment of mechanism-based therapeutic approaches. In this randomized, placebo-controlled, double-blinded crossover trial, 14 healthy volunteers were included. PEA (3 × 400 mg per day) or placebo were taken for 4 weeks. Our study investigated the mode of action of PEA using an established pain model, “Repetitive phasic heat application”, which is well-suited to investigate analgesic and anti-hyperalgesic effects in healthy volunteers. Parameters for peripheral and central sensitization as well as for pain modulation were assessed. Repetitive heat pain was significantly decreased, and the cold pain tolerance was significantly prolonged after the PEA treatment. The pressure pain tolerance and the conditioned pain modulation were increased after the PEA treatment. The wind-up ratio and the average distance of allodynia were significantly decreased after the PEA treatment. The heat pain tolerance was significantly higher after the PEA treatment. The present study has demonstrated that PEA has clinically relevant analgesic properties, acting on both peripheral and central mechanisms as well as in pain modulation.

Temporal Summation in Fibromyalgia Patients: Comparing Phasic and Tonic Paradigms

Introduction

Fibromyalgia (FM) is associated with dysfunctional pain modulation mechanisms, including central sensitization. Experimental pain measurements, such as temporal summation (TS), could serve as markers of central sensitization and have been previously studied in these patients, with conflicting results. Our objective in this study was to explore the relationships between two different protocols of TS (phasic and tonic) and test the associations between these measures and other clinical variables.

Materials and Methods

In this cross-sectional analysis of a randomized clinical trial, patients were instructed to determine their pain-60 test temperature, then received one train of 15 repetitive heat stimuli and rated their pain after the 1st and 15th stimuli: TSPS-phasic was calculated as the difference between those. We also administered a tonic heat test stimulus at the same temperature continuously for 30 s and asked them to rate their pain levels after 10 s and 30 s, calculating TSPS-tonic as the difference between them. We also collected baseline demographic data and behavioral questionnaires assessing pain, depression, fatigue, anxiety, sleepiness, and quality of life. We performed univariable analyses of the relationship between TSPS-phasic and TSPS-tonic, and between each of those measures and the demographic and clinical variables collected at baseline. We then built multivariable linear regression models to find predictors for TSPS-phasic and TSPS-tonic, while including potential confounders and avoiding collinearity.

Results

Fifty-two FM patients were analyzed. 28.85% developed summation during the TSPS-phasic protocol while 21.15% developed summation during the TSPS-tonic protocol. There were no variables associated TSPS phasic or tonic in the univariable analyses and both measures were not correlated. On the multivariate model for the TSPS-phasic protocol, we found a weak association with pain variables. BPI-pain subscale was associated with more temporal summation in the phasic protocol (ß = 0.38, p = 0.029), while VAS for pain was associated with less summation in the TSPS-tonic protocol (ß = −0.5, p = 0.009).

Conclusion

Our results suggest that, using heat stimuli with pain-60 temperatures, a TSPS-phasic protocol and a TSPS-tonic protocol are not correlated and could index different neural responses in FM subjects. Further studies with larger sample sizes would be needed to elucidate whether such responses could help differentiating subjects with FM into specific phenotypes.

Prevalence, Incidence, and Factors Associated With Non-Specific Chronic Low Back Pain in Community-Dwelling Older Adults Aged 60 Years and Older: A Systematic Review and Meta-Analysis

Chronic low back pain (CLBP) is common among older adults. This systematic review aimed to summarize: (1) the prevalence and incidence of CLBP in older adults, and (2) demographic, psychological, and clinical factors positively/negatively associated with prevalence/incidence of CLBP among older adults. Four databases were searched to identify relevant publications. Ten studies (31,080 older adults) were included after being screened by 5 independent reviewers using predetermined criteria. The methodological quality of these studies was evaluated by standardized tools. The quality of evidence for all factors were appraised by modified GRADE for cohort studies. Twenty-eight and 1 factors were associated with a higher prevalence and a lower 5-year cumulative incidence of CLBP, respectively. No prognostic factor was identified. There was very limited to limited evidence that females, obesity, anxiety, depression, mental disorders, self-expectation of recovery, self-perceived health status, lifestyle (smoking, daily fluoride consumption), previous falls or lower body injury, retirement/disability due to ill health, family history of body pain, comorbidity (knee osteoarthritis, or chronic obstructive pulmonary disease with/without hypertension), weak abdominal muscles, leg pain, leg pain intensity, widespread pain, pain interference on functioning, use of pain medication, occupational exposure (driving for >20 years, or jobs involving bending/twisting for >10 years), disc space narrowing and severe facet osteoarthritis were significantly related to a higher prevalence of CLBP in older adults. However, very limited evidence suggested that intermediate level of leisure-time physical activity was associated with a lower prevalence of CLBP in older adults. Given the aging population and limited information regarding risk factors for CLBP in older adults, future high-quality prospective studies should identify relevant risk factors to help develop proper preventive and treatment strategies. PERSPECTIVE: Despite the high prevalence of non-specific chronic low back pain among older adults, there is only very limited to limited evidence regarding factors associated with a higher prevalence of chronic low back pain in this population. Given the aging population, high-quality prospective studies are warranted to address this gap.

A novel computational technique for the quantification of temporal summation in healthy individuals

BACKGROUND

The pathophysiology of chronic musculoskeletal pain is linked to the neurophysiologic condition known as central sensitization. Developing reliable, sensitive and clinically feasible techniques for quantifying central sensitization is a timely priority for advancing the field of chronic pain diagnosis and management.

OBJECTIVE

To compare the sensitivity of the Windup Ratio, a commonly employed Quantitative Sensory Testing (QST) technique, to a novel approach, the Sumsquare method, for detecting changes in experimentally induced central sensitization.

DESIGN

Individual, randomized, controlled experimental study.

METHODS

A total of 37 subjects assigned to experimental (N = 18) and control (N = 19) groups. Central sensitization was experimentally induced in the C5-C6 spinal segments using topical capsaicin (0.075%); controls received a non-sensitizing placebo (Lubriderm). Windup (temporal summation) was assessed using weighted pinpricks (MRC Systems, Heidelberg, Germany) applied within regions of secondary hyperalgesia surrounding the topical capsaicin. A train of 10 stimuli was applied at baseline, 10, 20 and 30 min post-topical application and participants provided numeric pain ratings after each pinprick application. Sumsquare and Windup Ratio outcomes were calculated using the pain rating data.

RESULTS

Sumsquare outcome was significantly increased at all time points (10, 20, 30 min) post-sensitization (p < 0.05); in contrast, no differences in Windup Ratio from baseline were observed at any time point post-sensitization (p > 0.05).

CONCLUSIONS

Sumsquare outcome offers greater sensitivity than Windup Ratio for detecting changes in experimentally induced central sensitization. These findings introduce a novel method for assessing changes in central sensitization in patients presenting with chronic musculoskeletal pain hypersensitivity.

Association of temporomandibular disorders with pain sensitivity: A cohort study

BACKGROUND

Pain related to temporomandibular disorders (TMD) can be linked with multiple site pain (MSP), and may associate with increased pain sensitivity, more frequently among women than men. The aim of the study was to examine the associations of pressure pain threshold (PPT) and tolerance (PPTo) with TMD and associated MSP in the Northern Finland Birth Cohort 1966 (NFBC1966) study.

METHODS

Altogether 1961 NFBC1966 subjects attended clinical medical and dental examination at the Institute of Dentistry, University of Oulu in 2012-2013. Clinical examinations were carried out using a modified Diagnostic Criteria for TMD protocol (DC/TMD). MSP was defined based on questions regarding body pain sites. Additionally, PPT and PPTo were assessed using algometer measurements. Mann-Whitney U-test and Tobit regression models were used to analyse associations between TMD sub-diagnoses, MSP, PPT and PPTo, stratified by sex. Further models were adjusted with anxiety and depressive symptoms, which were assessed using Hopkins Symptom Checklist-25 (HSCL-25) and two-way interaction terms.

RESULTS

Among females, lower PPT and PPTo were associated with myalgia and arthralgia. Among males, lower PPT and PPTo were associated with MSP-linked TMD. Tobit regression analysis showed significantly lower PPT and PPTo values in the myalgia and arthralgia subgroups among female TMD subjects. Among females, disc displacement with reduction had an inverse association with PPT and PPTo. Among males, lower PPTo was associated with degenerative joint disease and MSP-linked TMD.

CONCLUSIONS

The pain regulatory mechanisms behind TMD act differently between the genders as local TMD among females and MSP-linked TMD among males were associated with pain sensitivity.

SIGNIFICANCE

The study shows that there are differences in the associations of painful TMD with pressure pain tolerance, pressure pain sensitivity and MSP between male and female subjects.

Exploring the Domains of Gender as Measured by a New Gender, Pain and Expectations Scale

Background: While sex- or gender-based differences in pain expression have been documented, exploration of traditionally genderized traits on pain has been hampered by the lack of strong measurement tools. This study evaluated the structural validity of a 16-item "Gender personality traits" subscale of a recently developed Gender, Pain and Expectations Scale (GPES). Methods: Data were drawn from an existing database of 248 participants (65.7% female). Maximum likelihood-based confirmatory factor analysis was carried out while considering the conceptual meaningfulness of subscales to evaluate the factor structure identified by these traits. Construct validity was explored using a priori hypotheses regarding anticipated mean differences in scores between biological male and female participants. Results: A meaningful factor structure could not be defined with all 16 items. Through conceptual and statistical triangulation a three-factor structure informed by 10 items was identified that satisfied acceptable fit criteria. The factors were termed "Emotive," "Relationship-Oriented," and "Goal-Oriented." Evidence of construct validity was supported through significant sex-based differences (p ≤ 0.02) in the expected directions for all three subscales. Conclusions: Review of the items in the three factors led the researchers to endorse a move away from naming these "masculine" and "feminine," rather focusing on the nature of the traits: "Relationship-oriented," "Emotive," and "Goal-oriented." Implications for researchers conducting sex/gender-based pain research are discussed. Clinical Trial Registration number: NCT02711085.

Functional Change in Experimental Allodynia After Glutamate-Induced Pain in the Human Masseter Muscle

Background: Glutamate, as well as nerve growth factor (NGF), is involved in nociception from peripheral tissues, such as muscles. However, the potential interaction between glutamate and NGF still remains unclear. This study investigated the interaction between glutamate-induced masseter muscle pain and NGF-induced allodynia on pain perception and jaw function in healthy individuals, and any possible sex differences in the response.

Materials and Methods: Thirty pain-free adult participants (15 men and 15 women, mean age ± SD: 24 ± 4 years) participated in this study consisting of three sessions (Day 0, Day 3, and Day 4). NGF (5 μg/mL, 1.0 mL) was injected into the masseter muscle on Day 0 to induce muscle allodynia. On Day 3, glutamate (1M, 0.2 mL) was injected into the same masseter muscle. Before and after injections on Day 0 and 3, and post-injection (Day 4), spontaneous pain, temporal summation pain, as well as functional pain and fatigue in response to chewing were assessed with validated scales, and the pressure pain threshold (PPT) was recorded.

Results: Spontaneous pain intensity was significantly higher after glutamate than NGF (P < 0.001). PPTs, temporal summation pain and functional measures were all reduced 3 days after NGF injection (P's < 0.001). Injection of glutamate on Day 3 did not further affect PPTs or temporal summation pain and there were no sex differences in the effects (P > 0.189). Chewing pain (P = 0.022) and fatigue increased after glutamate injection to a higher degree in the women than men (P = 0.037).

Conclusion: Taken together, while glutamate injected into the NGF-sensitized muscle was painful, it did not alter muscle tenderness in women vs. men. However, pain and fatigue evoked by jaw function were higher in women after glutamate injection. This suggest that sex differences reported for masseter myalgia, mimicked by glutamate and NGF mediated pain in this study, may be greater for measures of perceived jaw function, which should be considered in a clinical evaluation.

Controlled manual loading of body tissues: towards the next generation of pressure algometer

Assessing the responses of body tissue subjected to mechanical load is a fundamental component of the clinical examination, psychophysical assessments and bioengineering research. The forces applied during such assessments are usually generated manually, via the hands of the tester, and aimed at discreet tissue sites. It is therefore desirable to objectively quantify and optimise the control of manually applied force. However, current laboratory-grade manual devices and commercial software packages, in particular pressure algometer systems, are generally inflexible and expensive. This paper introduces and discusses several principles that should be implemented as design goals within a flexible, generic software application, given currently available force measurement hardware. We also discuss pitfalls that clinicians and researchers might face when using current pressure algometer systems and provide examples of these. Finally, we present our implementation of a pressure algometer system that achieves these goals in an efficient and affordable way for researchers and clinicians. As part of this effort, we will be sharing our configurable software application via a software repository.

Eye Conditions in Women

Changes in vision can have significant impact on health and quality of life. Differences between women and men have been identified in the incidence of several eye conditions. Some of these differences are a result of the greater longevity of women. However, the eye, like other organs, is susceptible to the impacts of inflammation and sex steroids. Conditions, such as thyroid eye disease, optic neuritis, and dry eye disease are related to autoimmune or inflammatory conditions and are, thus, more common among women. Idiopathic intracranial hypertension occurs disproportionately in women of childbearing age; the etiology of this condition appears to be related to both inflammatory and sex hormone fluctuations.

Emotion Measurements Through the Touch of Materials Surfaces

The emotion generated by the touch of materials is studied via a protocol based on blind assessment of various stimuli. The human emotional reaction felt toward a material is estimated through (i) explicit measurements, using a questionnaire collecting valence and intensity, and (ii) implicit measurements of the activity of the autonomic nervous system, via a pupillometry equipment. A panel of 25 university students (13 women, 12 men), aged from 18 to 27, tested blind twelve materials such as polymers, sandpapers, wood, velvet and fur, randomly ordered. After measuring the initial pupil diameter, taken as a reference, its variation during the tactile exploration was recorded. After each touch, the participants were asked to quantify the emotional value of the material. The results show that the pupil size variation follows the emotional intensity. It is significantly larger during the touch of materials considered as pleasant or unpleasant, than with the touch of neutral materials. Moreover, after a time period of about 0.5 s following the stimulus, the results reveal significant differences between pleasant and unpleasant stimuli, as well as differences according to gender, i.e., higher pupil dilatation of women than men. These results suggest (i) that the autonomic nervous system is initially sensitive to high arousing stimulation, and (ii) that, after a certain period, the pupil size changes according to the cognitive interest induced and the emotional regulation adopted. This research shows the interest of the emotional characterization of materials for product design.

Pain Intensity and Pain Interference in Male and Female Iraq/Afghanistan-era Veterans

BACKGROUND

Chronic pain conditions are common among both male and female Iraq/Afghanistan-era veterans and can have substantial negative impacts on quality of life and function. Although in general women tend to report higher levels of pain intensity than men, findings remain mixed on whether gender differences in pain exist in Iraq/Afghanistan-era veterans. Additionally, the relationships between functional impairment, pain intensity, and gender remain unknown.

METHODS

This project examined gender differences in pain intensity and pain interference in 875 male and female Iraq/Afghanistan-era veterans. Nonparametric Wilcoxon rank-tests examined gender differences in pain scores. Multivariable generalized linear regression modeling was used to evaluate the magnitude of pain intensity and interference across levels of chronicity and gender, and to evaluate the role of chronicity in gender effects in measures of pain and function.

RESULTS

Pain intensity and interference scores were significantly greater among both male and female veterans reporting chronic pain relative to acute pain. Women veterans endorsed higher levels of pain intensity and pain interference compared with men. Results derived from multivariable analyses implicated pain intensity as a factor underlying gender differences in functional impairment among chronic pain sufferers, indicating that gender differences in functional measures were eliminated after controlling statistically for pain intensity.

CONCLUSIONS

Results demonstrate that the effects of functional impairment are impacted by pain intensity, and not by gender.

Evaluating psychosocial contributions to chronic pain outcomes

The biopsychosocial model of pain dominates the scientific community's understanding of chronic pain. Indeed, the biopsychosocial approach describes pain and disability as a multidimensional, dynamic integration among physiological, psychological, and social factors that reciprocally influence one another. In this article, we review two categories of studies that evaluate the contributions of psychosocial factors to the experience of chronic pain. First, we consider general psychosocial variables including distress, trauma, and interpersonal factors. Additionally, we discuss pain-specific psychosocial variables including catastrophizing, expectations, and pain-related coping. Together, we present a diverse array of psychological, social, and contextual factors and highlight the need to consider their roles in the development, maintenance, and treatment of chronic pain conditions.

Age and gender differences in mechanically induced intraoral temporal summation and conditioned pain modulation in healthy subjects

OBJECTIVE

The aim of this study was to investigate intraoral temporal summation (TS) and conditioned pain modulation (CPM) and compare the outcome with TS and CPM induced in the forearm. In addition, we aimed to study the effect of age and gender on intraoral and forearm TS and CPM.

STUDY DESIGN

Mechanical stimulation was induced with # 5.46 von Frey filament applying 26 grams of force. A single stimulus, followed by a train of 30 successive stimuli, was applied intraorally and to the dominant forearm. CPM was assessed with the TS test as the painful stimulus and with immersion of the nondominant hand in a hot water bath as the conditioning stimulus.

RESULTS

Gender was significantly associated with TS but not with CPM measures. Females had significantly lower mean TS measured in the face and in the dominant forearm compared with males. Age was significantly associated with CPM, but not with TS measures. In both sites examined, older patients had significantly lower mean CPM compared with younger patients.

CONCLUSIONS

Mechanical TM elicited in the oral cavity can be used as test stimulus for CPM testing. Intraoral modulation, both TS and CPM, has an extent similar to that of the standard cutaneous extremity. TS was lower in females, and CPM was reduced with age.

Sex-Specific Effects of Gender Identification on Pain Study Recruitment

Epidemiological, clinical, and laboratory studies show sex differences in pain responses, with women more sensitive to nociceptive stimulation and more vulnerable to long-term pain conditions than men. Because of evidence that men are culturally reinforced for the ability to endure (or under-report) pain, some of these findings might be explained by sociocultural beliefs about gender-appropriate behavior. One potential manifestation of these effects might be differential participation in pain studies, with men adhering to stereotypical masculine roles viewing participation as a way to demonstrate their masculinity. To test this possibility, we assessed gender identification in 137 healthy participants. At the end of the assessment, they were asked if they would like to participate in other research studies. Interested participants were then asked to participate in a study involving administration of pain-evoking stimulation. We compared individuals who agreed to participate in the pain study with those who declined. We observed a significant Sex × Participation interaction in masculine gender identification, such that men (but not women) who agreed to participate identified significantly more with masculine gender. Among masculine gender traits examined, we found that high levels of aggression and competitiveness were the strongest predictors of pain study participation. Our results suggest that men in pain studies might have higher levels of masculine gender identification than the wider male population. Taken together with previous findings of lower levels of pain sensitivity (or reporting) in masculine-identifying male participants, these results suggest an explanation for some of the sex-related differences observed in pain responses.

PERSPECTIVE

To examine whether sex and gender affect willingness to participate in pain studies, we assessed gender identification in men and women, then attempted to recruit them to participate in a pain study. Men who agree to participate in pain studies are significantly higher in masculine gender identification than men who decline to participate or women who agree to participate. Men who agreed to participate were rated particularly high in aggressiveness and competitiveness.

Effects of measurement posture and stimulation intensity on the nociceptive flexion reflex (RIII reflex)

[Purpose] The purpose of this study was to examine the effects of the measurement posture and stimulation intensity on the nociceptive flexion reflex (RIII reflex). [Subjects and Methods] Thirty normal female adult subjects were selected for this study. Their RIII reflexes were measured in three positions and with three degrees of stimulation intensity. The measurement posture was randomly selected. The analysis items were the stimulation intensity of the induced RIII reflex, the amplitude of the RIII reflex, and the numeric rating scale (NRS). [Results] The study results showed statistically significant differences in the interaction effects between the measurement posture and the stimulation intensity. The NRS showed no statistically significant differences in the interaction effects but showed statistically significant differences in the main effect. The amplitude of the RIII reflex showed no statistically significant differences in the interaction effects and showed statistically significant differences only in the stimulation intensity. [Conclusion] The study results suggest that the RIII reflex may be influenced by the measurement posture and stimulation intensity.

Low back pain in older adults: risk factors, management options and future directions

Low back pain (LBP) is one of the major disabling health conditions among older adults aged 60 years or older. While most causes of LBP among older adults are non-specific and self-limiting, seniors are prone to develop certain LBP pathologies and/or chronic LBP given their age-related physical and psychosocial changes. Unfortunately, no review has previously summarized/discussed various factors that may affect the effective LBP management among older adults. Accordingly, the objectives of the current narrative review were to comprehensively summarize common causes and risk factors (modifiable and non-modifiable) of developing severe/chronic LBP in older adults, to highlight specific issues in assessing and treating seniors with LBP, and to discuss future research directions. Existing evidence suggests that prevalence rates of severe and chronic LBP increase with older age. As compared to working-age adults, older adults are more likely to develop certain LBP pathologies (e.g., osteoporotic vertebral fractures, tumors, spinal infection, and lumbar spinal stenosis). Importantly, various age-related physical, psychological, and mental changes (e.g., spinal degeneration, comorbidities, physical inactivity, age-related changes in central pain processing, and dementia), as well as multiple risk factors (e.g., genetic, gender, and ethnicity), may affect the prognosis and management of LBP in older adults. Collectively, by understanding the impacts of various factors on the assessment and treatment of older adults with LBP, both clinicians and researchers can work toward the direction of more cost-effective and personalized LBP management for older people.

Level of pain and quality of life of people living with HIV/AIDS pain and quality of life in HIV/AIDS

The aim of this descriptive study was to correlate the level of pain with the quality of life in 261 people living with HIV/AIDS. Mild pain/no pain was reported by 47.5% of subjects, 24.1% reported moderate pain, and 28.4% reported severe pain; pain levels were correlated with gender (p = 0.02), health status (p < 0.001), perception (p < 0.001), and stage of infection (p = 0.005). Being female represented a risk factor for moderate (p < 0.001) and intense pain (p = 0.004). Poor health represented a risk for moderate (p < 0.038) and intense pain (p = 0.005). Being young was a factor of protection for moderate pain (21-30 years, p = 0.046; 41-50 years, p = 0.023; and 51-60 years, p < 0.030). The low quality of life averages was identified and correlated with pain in all evaluated domains (p < 0.001). The risk factors for moderate and severe pain were a low level of independence (p = 0.004) and compromised social relations (p = 0.029), respectively. Psychological control behaved as a protection factor for moderate pain (p = 0.011), and bad physical domain proved to be a protection factor for severe pain (p = 0.007). The level of pain is a negative impact on the quality of life of people with HIV/AIDS.

Different mechanosensory stimulations of the lower back elicit specific changes in hemodynamics and oxygenation in cortical sensorimotor areas-A fNIRS study

BACKGROUND AND OBJECTIVES

This study aimed at investigating the feasibility of functional near-infrared spectroscopy (fNIRS) to measure changes in cerebral hemodynamics and oxygenation evoked by painful and nonpainful mechanosensory stimulation on the lower back. The main objectives were to investigate whether cortical activity can be (1) detected using functional fNIRS, and (2) if it is possible to distinguish between painful and nonpainful pressure as well as a tactile brushing stimulus based on relative changes in oxy- and deoxyhemoglobin ([O2Hb] and [HHb]).

METHODS

Twenty right-handed subjects (33.5 ± 10.7 years; range 20-61 years; 8 women) participated in the study. Painful and nonpainful pressure stimulation was exerted with a thumb grip perpendicularly to the spinous process of the lumbar spine. Tactile stimulation was realized by a one-finger brushing. The supplementary motor area (SMA) and primary somatosensory cortex (S1) were measured bilaterally using a multichannel continuous-wave fNIRS imaging system.

RESULTS

Characteristic relative changes in [O2Hb] in the SMA and S1 after both pressure stimulations (corrected for multiple comparison) were observed. [HHb] showed only much weaker changes (uncorrected). The brushing stimulus did not reveal any significant changes in [O2Hb] or [HHb].

CONCLUSION

The results indicate that fNIRS is sensitive enough to detect varying hemodynamic responses to different types of mechanosensory stimulation. The acquired data will serve as a foundation for further investigations in patients with chronic lower back pain. The future aim is to disentangle possible maladaptive neuroplastic changes in sensorimotor areas during painful and nonpainful lower back stimulations based on fNIRS neuroimaging.

Cortical Sensorimotor Processing of Painful Pressure in Patients with Chronic Lower Back Pain-An Optical Neuroimaging Study using fNIRS

In this study we investigated sensorimotor processing of painful pressure stimulation on the lower back of patients with chronic lower back pain (CLBP) by using functional near-infrared spectroscopy (fNIRS) to measure changes in cerebral hemodynamics and oxygenation. The main objectives were whether patients with CLBP show different relative changes in oxy- and deoxyhemoglobin ([O2Hb] and [HHb]) in the supplementary motor area (SMA) and primary somatosensory cortex (S1) compared to healthy controls (HC). Twelve patients with CLBP (32 ± 6.1 years; range: 24-44 years; nine women) and 20 HCs (33.5 ± 10.7 years; range 22-61 years; eight women) participated in the study. Painful and non-painful pressure stimulation was exerted with a thumb grip perpendicularly to the spinous process of the lumbar spine. A force sensor was attached at the spinous process in order to control pressure forces. Tactile stimulation was realized by a one-finger brushing. Hemodynamic changes in the SMA and S1 were measured bilaterally using a multi-channel continuous wave fNIRS imaging system and a multi-distant probe array. Patients with CLBP showed significant stimulus-evoked hemodynamic responses in [O2Hb] only in the right S1, while the HC exhibited significant [O2Hb] changes bilaterally in both, SMA and S1. However, the group comparisons revealed no significant different hemodynamic responses in [O2Hb] and [HHb] in the SMA and S1 after both pressure stimulations. This non-significant result might be driven by the high inter-subject variability of hemodynamic responses that has been observed within the patients group. In conclusion, we could not find different stimulus-evoked hemodynamic responses in patients with CLBP compared to HCs. This indicates that neither S1 nor the SMA show a specificity for CLBP during pressure stimulation on the lower back. However, the results point to a potential subgrouping regarding task-related cortical activity within the CLBP group; a finding worth further research.

Gender differences between WOMAC index scores, health-related quality of life and physical performance in an elderly Taiwanese population with knee osteoarthritis

OBJECTIVE

To investigate the importance of the WOMAC index score, health-related quality of life and physical performance in each domain affected by knee osteoarthritis (OA) and to identify gender differences in the importance of these domains and physical performances.

MATERIAL AND METHODS

We performed a population-based study for radiographic knee OA among participants aged more than 65 years. Demographic data were collected and anthropometric measurement, radiographic assessment, the WOMAC index score, the short-form 12 (SF-12), the Timed and Up to Go Test (TUGT) and the Five Times Sit to Stand Test (FTSST) were performed.

RESULT

There were 901 individuals (409 males and 492 females) aged 74.04±6.92 (male: 76.35±7.33; female: 72.12±5.92) years included in this study. The WOMAC scores of participants with OA were higher than those without OA in males and females (male: 11.97±15.79 vs 8.23±12.84, p<0.001; female: 10.61±14.97 vs 7.59±3.31, p=0.032). The physical component summary (PCS) score was only significant in females with knee OA (62.14±24.66 vs 66.59±23.85, p=0.043), while the mental component summary (MCS) score was only significant in males with knee OA (78.02±18.59 vs 81.98±15.46, p=0.02). The TUGT and FTSST were not significant in individuals with and without OA in males and females. Moreover, the multivariate results for the WOMAC score were significant for females (3.928 (95% CI 1.287 to 6.569), p=0.004).

CONCLUSIONS

The PCS domains of SF-12 and MCS domains of SF-12 are crucial in Taiwanese females and elderly males, respectively, with knee OA. Different evaluation and treatment strategies based on gender differences should be considered in elderly Taiwanese patients with knee OA to improve their quality of life.

Individually based measurement of temporal summation evoked by a noxious tonic heat paradigm

BACKGROUND

A model for measuring temporal summation (TS) by tonic noxious stimulation was recently proposed. However, methodological variations between studies make it difficult to reach a consensus regarding the way TS should be applied and calculated. The present study aimed to present a calculation method of TS magnitude produced by a tonic heat model in a large cohort of healthy subjects.

METHODS

Noxious heat stimulation (46.5°C/2 minutes) was applied to the forearm of 154 subjects who continuously rated pain intensity using a computerized visual analog scale. TS was calculated by "mean group" and "individual" approaches.

RESULTS

A "typical" pattern of pain response, characterized by a peak pain followed by a decrease in intensity to a nadir and subsequently a progressive increase in pain scores, was exhibited by 86.4% of the subjects. Using the "mean group" and "individual" calculation approaches, the mean ± standard deviation magnitudes of TS were 31.4±27.5 and 41.0±26.0, respectively (P<0.001). Additionally, using the individualized approach, we identified a different ("atypical") response pattern among the rest of the subjects (13.6%).

CONCLUSION

The results support the tonic heat model of TS for future utilization. The individualized TS calculation method seems advantageous since it better reflects individual magnitudes of TS.

Sex Differences in Patients with Chronic Pain Following Whiplash Injury: The Role of Depression, Fear, Somatization, Social Support, and Personality Traits

BACKGROUND

Chronic whiplash-associated disorders (chronic WAD) cover a large variety of clinical manifestations that can occur after a whiplash injury. Women have an increased risk of developing chronic WAD, and it is suggested that psychosocial factors are related to long-term pain and functioning following whiplash injury and persistence of chronic pain. This leads to the question whether there are sex differences in psychosocial factors in chronic WAD.

METHODS

This study included 117 subjects who had experienced a whiplash injury at least 3 months before the start of the study (mean duration of pain: 67.29 ± 63.86 months, range: 297 months). They were selected as chronically symptomatic, by excluding those who had recovered from their whiplash injury. Psychosocial aspects (including depression, fear, somatization, social support, and personality traits) were assessed by validated questionnaires, and sex differences were tested using a univariate analysis of variance (ANCOVA), with age and time from whiplash injury as covariates.

RESULTS

No differences in depression, fear, somatization, discrepancy in social support personality trait, Neck Disability Index scores, physical functioning, bodily pain, or general health were present between women and men with chronic WAD. Women with chronic WAD reported higher levels of emotional support in problem situations and social companionship.

CONCLUSION

Except for emotional support in problem situations and social companionship, psychosocial factors do not differ between men and women with chronic WAD. These findings imply little to no risk for sex bias in studies investigating psychosocial issues in patients with chronic WAD.

Prevalence of neck and low back pain in community-dwelling adults in Spain: an updated population-based national study (2009/10-2011/12)

PURPOSE

To estimate time trends in the prevalence of neck (NP) and low back pain (LBP) from 2009 to 2012; and to determine the socio-demographic features, self-rated health status, co-morbidity, lifestyle-related habits, and health care service associated with NP and LBP in Spanish adults.

OUTCOME MEASURES

The European Health Interview Survey for Spain (2009) and the Spanish National Health Survey (2011).

METHODS

A total of 43,072 subjects were included. We analyzed data collected from the European Health Interview Survey for Spain conducted in 2009 (n = 22,188), and the Spanish National Health Survey in 2011 (n = 20,884). We considered the presence of isolated NP, LBP and both (NP&LBP). We analyzed socio-demographic features; self-perceived health status; lifestyle habits; comorbid diseases, and professional treatment using logistic regression models.

RESULTS

The prevalence of isolated NP, LBP and NP&LBP increased from 2008/9 to 2011/12 (7.86 vs. 8.56 %; 5.18 vs.5.44 %; 10.61 vs.11.12 %, respectively). Being female, increased the probability of isolated NP and NP&LBP, but decreased the probability of LBP. The prevalence of all pain localizations increased with older age, lower education level, poor self-rated health, smoker, comorbidities, psychological distress (anxiety or depression), hospital and physiotherapist visits and consumed drugs for pain, in 2008/9 as compared to 2011/12. Moreover, LBP, and NP&LBP were associated with obesity, whereas NP&LBP was associated with being married.

CONCLUSIONS

The prevalence of LBP, NP and NP&LBP had increased in the last 3 years in Spain.

Bone hyperalgesia after mechanical impact stimulation: a human experimental pain model

Hyperalgesia in different musculoskeletal structures including bones is a major clinical problem. An experimental bone hyperalgesia model was developed in the present study. Hyperalgesia was induced by three different weights impacted on the shinbone in 16 healthy male and female subjects. The mechanical impact pain threshold (IPT) was measured as the height from which three weights (165, 330, and 660 g) should be dropped to elicit pain at the shinbone. Temporal summation of pain to repeated impact stimuli was assessed. All these stimuli caused bone hyperalgesia. The pressure pain threshold (PPT) was assessed by a computerized pressure algometer using two different probes (1.0 and 0.5 cm(2)). All parameters were recorded before (0), 24, 72, and 96 h after the initial stimulations. The IPTs were lowest 24 h after hyperalgesia induction for all three weights and the effect lasted up to 72 h (p < 0.05). The PPT obtained with the 1.0 cm(2) probe was significantly lower than the PPT obtained with the 0.5 cm(2) probe, regardless of the time. Females developed more pronounced hyperalgesia reflected in reduced IPTs and PPTs (p < 0.05). Temporal summation was significantly (p < 0.05) facilitated after induction of hyperalgesia with the strongest facilitation in males. The developed bone pain and hyperalgesia model may provide the basis for studying this fundamental mechanism of bone-related hyperalgesia and be used for profiling compounds developed for this target.

Sex differences in mechanical allodynia: how can it be preclinically quantified and analyzed?

Translating promising preclinical drug discoveries to successful clinical trials remains a significant hurdle in pain research. Although animal models have significantly contributed to understanding chronic pain pathophysiology, the majority of research has focused on male rodents using testing procedures that produce sex difference data that do not align well with comparable clinical experiences. Additionally, the use of animal pain models presents ongoing ethical challenges demanding continuing refinement of preclinical methods. To this end, this study sought to test a quantitative allodynia assessment technique and associated statistical analysis in a modified graded nerve injury pain model with the aim to further examine sex differences in allodynia. Graded allodynia was established in male and female Sprague Dawley rats by altering the number of sutures placed around the sciatic nerve and quantified by the von Frey test. Linear mixed effects modeling regressed response on each fixed effect (sex, oestrus cycle, pain treatment). On comparison with other common von Frey assessment techniques, utilizing lower threshold filaments than those ordinarily tested, at 1 s intervals, appropriately and successfully investigated female mechanical allodynia, revealing significant sex and oestrus cycle difference across the graded allodynia that other common behavioral methods were unable to detect. Utilizing this different von Frey approach and graded allodynia model, a single suture inflicting less allodynia was sufficient to demonstrate exaggerated female mechanical allodynia throughout the phases of dioestrus and pro-oestrus. Refining the von Frey testing method, statistical analysis technique and the use of a graded model of chronic pain, allowed for examination of the influences on female mechanical nociception that other von Frey methods cannot provide.

Neural and psychosocial contributions to sex differences in knee osteoarthritic pain

People with osteoarthritis (OA) can have significant pain that interferes with function and quality of life. Women with knee OA have greater pain and greater reductions in function and quality of life than men. In many cases, OA pain is directly related to sensitization and activation of nociceptors in the injured joint and correlates with the degree of joint effusion and synovial thickening. In some patients, however, the pain does not match the degree of injury and continues after removal of the nociceptors with a total joint replacement. Growth of new nociceptors, activation of nociceptors in the subchondral bone exposed after cartilage degradation, and nociceptors innervating synovium sensitized by inflammatory mediators could all augment the peripheral input to the central nervous system and result in pain. Enhanced central excitability and reduced central inhibition could lead to prolonged and enhanced pain that does not directly match the degree of injury. Psychosocial variables can influence pain and contribute to pain variability. This review explores the neural and psychosocial factors that contribute to knee OA pain with an emphasis on differences between the sexes and gaps in knowledge.

In vivo and in vitro comparison of female and male nociceptors

While it is generally accepted that women have lower pain thresholds for diverse forms of noxious stimuli, the mechanistic basis for this sexual dimorphism in nociceptive pain remains to be elucidated. We confirmed, in the rat, that females have lower cutaneous mechanical nociceptive thresholds and established a similar sexual dimorphism in muscle. To determine if a peripheral mechanism underlies this sexual dimorphism in pain threshold, we compared biophysical properties of cultured dorsal root ganglion (DRG) neurons that innervated the gastrocnemius muscle in female and male rats. DRG neurons from female rats, which innervated the gastrocnemius muscle, had a more hyperpolarized resting membrane potential. To determine if this was associated with a higher mechanical nociceptive threshold, in contradiction to our working hypothesis, we compared the function, in vivo, of nociceptive afferents innervating the gastrocnemius muscle in male and female rats. C-fiber nociceptors innervating muscle in female rats had higher mechanical thresholds than those in males. Other response characteristics of these nociceptors were not significantly different. Thus, both in vitro and in vivo electrophysiology experiments support the idea that lower mechanical nociceptive threshold in females may be due to sexual dimorphism in central nervous system mechanisms, a difference large enough to overcome an opposing difference in peripheral pain mechanisms.

PERSPECTIVE

This article unifies in vivo and in vitro electrophysiology with behavioral data examining the differences in mechanical nociceptive threshold between male and female rats. The data provide a novel perspective on the peripheral and behavioral outcomes of noxious mechanical stimulation.

Post-dural (post-lumbar) puncture headache: risk factors and clinical features

OBJECTIVE

This is an analytic, interventional, cross sectional study to evaluate the risk factors of post-dural (post-lumbar) puncture headache (PDPH) and the validity of the diagnostic criteria for PDPH from the ICHD II.

METHODS

Six-hundred-and-forty patients (332 non-pregnant women and 308 men) aged 8-65 years underwent spinal anesthesia with Quincke 25G or 27G needles in elective surgery.

RESULTS

Forty-eight (7.5%) of the patients developed PDPH. The binary logistic regression analysis identified as risk factors: gender [11.1% female vs. 3.6% male, OR 2.25 (1.07-4.73); p = 0.03], age [11.0% 31-50 years of age vs. 4.2% others, OR 2.21 (1.12-4.36); p = 0.02], previous history of PDPH [26.4% positive vs. 6.2% negative, OR 4.30 (1.99-9.31); p < 0.01] and bevel orientation [16.1% perpendicular vs. 5.7% parallel, OR 2.16 (1.07-4.35); p = 0.03]. The period of latency between lumbar puncture and headache onset range from 6 to 72 hours and the duration from 3 to 15 days. In 34/48 (71%) patients with PDPH, at least one of the following was present: neck stiffness, tinnitus, hypoacusia, photophobia, or nausea.

CONCLUSION

In conclusion, 14/48 patients (29%) suffered none of the above-mentioned symptoms, indicating that a significant number of patients may suffer from PDPH in the absence of any symptoms apart from the headache itself. This suggests that a further analyses of existing studies should be made to determine if a criteria change may need consideration.

A systematic literature review of 10 years of research on sex/gender and experimental pain perception - part 1: are there really differences between women and men?

The purpose of this systematic review was to summarize and critically appraise the results of 10 years of human laboratory research on pain and sex/gender. An electronic search strategy was designed by a medical librarian and conducted in multiple databases. A total of 172 articles published between 1998 and 2008 were retrieved, analyzed, and synthesized. The first set of results (122 articles), which is presented in this paper, examined sex difference in the perception of laboratory-induced thermal, pressure, ischemic, muscle, electrical, chemical, and visceral pain in healthy subjects. This review suggests that females (F) and males (M) have comparable thresholds for cold and ischemic pain, while pressure pain thresholds are lower in F than M. There is strong evidence that F tolerate less thermal (heat, cold) and pressure pain than M but it is not the case for tolerance to ischemic pain, which is comparable in both sexes. The majority of the studies that measured pain intensity and unpleasantness showed no sex difference in many pain modalities. In summary, 10 years of laboratory research have not been successful in producing a clear and consistent pattern of sex differences in human pain sensitivity, even with the use of deep, tonic, long-lasting stimuli, which are known to better mimic clinical pain. Whether laboratory studies in healthy subjects are the best paradigm to investigate sex differences in pain perception is open to question and should be discussed with a view to enhancing the clinical relevance of these experiments and developing new research avenues.

Prevalence of chronic head, neck and low back pain and associated factors in women residing in the Autonomous Region of Madrid (Spain)

OBJECTIVE

To compare the prevalence of chronic headache (CH), chronic neck pain (CNP) and chronic low back pain (CLBP) in the autonomous region of Madrid by analyzing gender differences and to determine the factors associated with each pain location in women in 2007.

METHODS

We analyzed data obtained from adults aged 16 years or older (n = 12,190) who participated in the 2007 Madrid Regional Health Survey. This survey includes data from personal interviews conducted in a representative population residing in family dwellings in Madrid. The presence CH, CNP, and CLBP was analyzed. Sociodemographic features, self-perceived health status, lifestyle habits, psychological distress, drug consumption, use of healthcare services, the search for alternative solutions, and comorbid diseases were analyzed by using logistic regression models.

RESULTS

The prevalence of CH, CNP and CLBP was significantly higher (P<0.001) in women (7.3%, 8.4%, 14.1%, respectively) than in men (2.2%, 3.2%, 7.8%, respectively). In women, CH, CNP and CBLP were significantly associated with having ≥3 chronic diseases (OR 7.1, 8.5, 5.8, respectively), and with the use of analgesics and drugs for inflammation (OR: 3.5, 1.95, 2.5, respectively). In the bivariate analysis, the factors associated with pain in distinct body locations differed between men and women.

CONCLUSIONS

This study found that CH, CNP and CLBP are a major public health problem in women in central Spain. Women have a higher overall prevalence of chronic pain than men. Chronic pain was associated with a higher use of analgesics and healthcare services.

Increased pain sensitivity is not associated with electrodiagnostic findings in women with carpal tunnel syndrome

OBJECTIVE

To determine the differences in widespread pressure pain and thermal hypersensitivity in women with minimal, moderate, and severe carpal tunnel syndrome (CTS) and healthy controls.

METHODS

A total of 72 women with CTS (19 with minimal, 18 with moderate, and 35 with severe) and 19 healthy age-matched women participated. Pressure pain thresholds were bilaterally assessed over the median, ulnar, and radial nerves, the C5 to C6 zygapophyseal joint, the carpal tunnel, and the tibialis anterior muscle. In addition, warm and cold detection thresholds and heat and cold pain thresholds were bilaterally assessed over the carpal tunnel and the thenar eminence. All outcome parameters were assessed by an assessor blinded to the participant's condition.

RESULTS

No significant differences in pain parameters among patients with minimal, moderate, and severe CTS were found. The results showed that PPT were significantly decreased bilaterally over the median, ulnar, and radial nerve trunks, the carpal tunnel, C5 to C6 zygapophyseal joint, and the tibialis anterior muscle in patients with minimal, moderate, or severe CTS as compared with healthy controls (all, P<0.001). In addition, patients with CTS also showed lower heat pain threshold and reduced cold pain threshold compared with controls (P<0.001). No significant sensory differences between minimal, moderate, or severe CTS were found.

CONCLUSIONS

The similar widespread pressure and thermal hypersensitivity in patients with minimal, moderate, or severe CTS and pain intensity suggests that increased pain sensitivity is not related to electrodiagnostic findings.

A systematic literature review of 10 years of research on sex/gender and pain perception - part 2: do biopsychosocial factors alter pain sensitivity differently in women and men?

This systematic review summarizes the results of 10 years of laboratory research on pain and sex/gender. An electronic search strategy was designed by a medical librarian to access multiple databases. A total of 172 articles published between 1998 and 2008 were retrieved, analyzed, and synthesized. The second set of results presented in this review (129 articles) examined various biopsychosocial factors that may contribute to differences in pain sensitivity between healthy women and men. The results revealed that the involvement of hormonal and physiological factors is either inconsistent or absent. Some studies suggest that temporal summation, allodynia, and secondary hyperalgesia may be more pronounced in women than in men. The evidence to support less efficient endogenous pain inhibitory systems in women is mixed and does not necessarily apply to all pain modalities. With regard to psychological factors, depression may not mediate sex differences in pain perception, while the role of anxiety is ambiguous. Cognitive and social factors appear to partly explain some sex-related differences. Finally, past individual history may be influential in female pain responses. However, these conclusions must be treated with much circumspection for various methodological reasons. Furthermore, some factors/mechanisms remain understudied in the field. There is also a need to assess and improve the ecological validity of findings from laboratory studies on healthy subjects, and perhaps a change of paradigm needs to be considered at this point in time to better understand the factors that influence the experience of women and men who suffer from acute or chronic pain.