Age and race effects on pain sensitivity and modulation among middle-aged and older adults

Preliminary Characterization of Age and Chronic Low Back Pain Effects on Multimodal Pain Sensitivity: A Comparison Study in Older Adults with and Without Chronic Low Back Pain

Though pain sensitivity impairments contribute to chronic pain in younger adults, it is unclear if pain hypersensitivity manifests with aging and is heightened in the geriatric chronic low back pain population. The cross-sectional study preliminarily addressed this gap by measuring pain sensitivity in older adults with chronic low back pain (n = 25) as well as pain-free sex-matched older (n = 25) and younger adults (n = 25). Pain sensitivity was quantified by 8 distinct measures that were subdivided as static (ie, pressure pain thresholds, heat pain thresholds, fixed mechanical pain, and fixed cold pain) and dynamic pain sensitivity (ie, mechanical temporal summation, thermal ramp and hold, heat pain aftersensations, and conditioned pain modulation). Test-retest reliability values for pain sensitivity ranged from moderate to excellent (intraclass correlation coefficients ≥ .500; p's < .05). The main effect for the group was significant (partial η2 = .413, P < .001), revealing between-group differences in pain sensitivity on 5 out of 8 tests (p's ≤ .043). Predominantly, both older adult groups demonstrated increased pain facilitation and decreased pain inhibition during dynamic pain sensitivity testing compared to pain-free younger adults (p's ≤ .044). Despite qualitative differences, static and dynamic pain sensitivity responses were statistically similar between older adults with and without chronic LBP (p's > .05). Findings suggest pain sensitivity can be reliably measured in older adults and that pain hypersensitivity develops with chronological aging, providing partial support for the theory that pain hypersensitivity may impact geriatric chronic pain populations. Further study is needed to more definitively parse out whether pain hypersensitivity is comparatively heightened in older adults with chronic LBP beyond the influence of chronological aging. PERSPECTIVE: This article establishes that surrogate measures of centrally mediated pain sensitization are heightened with aging. Impaired endogenous pain modulation may influence chronic pain development, maintenance, treatment efficacy, and/or ensuing disability, necessitating research to comprehensively characterize how pain hypersensitivity contributes to geriatric chronic pain conditions.

Changes in Widespread Pain After Surgical Weight Loss in Racialized Adults: A Secondary Analysis From a 2-Year Longitudinal Study

Widespread pain (WP) is associated with reduced function and disability. Importantly, three-fourths of the approximately 42% of U.S. adults with obesity have WP. Moreover, rates of adult obesity are higher, and WP outcomes are worse in racialized non-Hispanic Black and Hispanic/Latino/a/X groups, potentially exacerbating existing pain disparities. Bariatric surgery significantly reduces weight and improves pain. However, recurrent or unresolved pain after bariatric surgery can hinder weight loss or facilitate weight regain. The current study conducted a secondary analysis of a longitudinal study of predictors and mechanisms of weight loss after bariatric surgery to examine the point prevalence of WP and pain trajectories 24 months post surgery. Our secondary aim was to examine the association between weight loss and pain characteristics. Our exploratory aim was to longitudinally examine racial differences in pain trajectories after bariatric surgery. Our results showed that point prevalence decreased after bariatric surgery. Additionally, significant improvements in pain trajectories occurred within the first 3 months post surgery with a pattern of pain reemergence beginning at 12 months post surgery. Hispanic/Latino/a/X participants reported a higher number of painful anatomical sites before bariatric surgery, and the rate of change in this domain for this group was faster compared with the racialized non-Hispanic Black participants. These findings suggest that pain improvements are most evident during the early stages of surgical weight loss in racialized populations of adults with WP. Thus, clinicians should routinely monitor patients' weight changes after bariatric surgery as they are likely to correspond to changes in their pain experiences. PERSPECTIVE: This article presents the prevalence and pain trajectories of racialized adults with WP after surgical weight loss. Clinicians should evaluate changes in the magnitude and spatial distribution of pain after significant weight change in these populations so that pain interventions can be prescribed with greater precision.

The comparison of effectiveness of acupressure on Spleen 6 and Hugo points on the severity of postpartum pain: A randomized clinical trial

Background and aims

Postpartum pain poses a significant challenge for new mothers. Various nonpharmacological methods are employed to manage postpartum pain. This study aimed to compare the effectiveness of acupressure on Spleen 6 and Hugo points on the severity of postpartum pain.

Methods

In this parallel randomized trial study, 68 eligible primiparous women who had vaginal deliveries and experienced postpartum pain at Farabi Hospital in Malekan (a city in East Azarbaijan Province in Iran) were selected according to inclusion/exclusion criteria and then allocated to the Hugo (n = 34) and Spleen 6 (n = 34) acupressure groups using a randomized block design (six blocks). The data collection process took place from November 2022 to April 2023. The participants were blinded; however, the analysts and investigators were not blinded. Acupressure interventions were applied bilaterally for 20 min, consisting of 10 s of pressure followed by 2 s of rest. Pain intensity was assessed using a visual pain scale before, immediately after, and 1 h after the intervention. In total, 68 participants fulfilled the study. Data were analyzed using Statistical Package for the Social Sciences version 25 with chi-square, Mann-Whitney, and Friedman tests.

Results

Both groups exhibited a statistically significant reduction in postpartum pain intensity across all periods (p < 0.001). Although there was a significant difference in pain intensity between the groups before the intervention (p = 0.039), this distinction was not observed immediately and 1 h after the intervention (p ≥ 0.05). Both Hugo and Spleen's 6 acupressure interventions reduced postpartum pain intensity. No significant adverse events or side effects were observed.

Conclusion

Acupressure on Spleen 6 and Hugo points helped decrease the severity of postpartum pain in primiparous women who had vaginal deliveries. Healthcare providers are encouraged to consider acupressure for postpartum pain management.

Age and Sex Differences of Virtual Reality Pain Alleviation Therapeutic During Pediatric Burn Care: A Randomized Clinical Trial

Virtual reality (VR) effectively alleviates pain for pediatric patients during many medical procedures, such as venipuncture and burn care. In our previously published randomized clinical trial among 90 pediatric burn patients, participants in the active VR group had significantly lower scores for overall pain compared with participants in the standard care control and for worst pain compared with participants in the passive VR and control group. However, whether VR differs by a patient's age or sex remains unresolved. Thus, we reanalyzed our data by comparing the active and passive VR participants to evaluate how age and sex affect VR pain alleviation during dressing care for pediatric burns. In total, 90 patients aged 6-17 years (inclusive) with burn injuries were recruited from an outpatient burn clinic of an American Burn Association-verified pediatric burn center. Before randomization, VR helpfulness and need expectations were assessed on a visual analog scale (0-100). Participants were randomly assigned to active VR, passive VR, or control for one dressing change. Immediately following the dressing change, active and passive VR participants self-reported pain and the time spent thinking about pain and rated the VR features on the degree of realism, pleasure/fun, and perceived engagement level. Path analyses assessed how these VR features were interrelated and how they affected self-reported pain by age and sex. Patients aged 6-9 years reported higher mean expectations of VR helpfulness and need (mean = 73.6 and 94.5, respectively) than 10-12-year-olds (mean = 55.7 and 84.2, respectively) and 13-17-year-olds (mean = 68.6 and 77.4, respectively). The path analysis indicated VR engagement and fun were significantly correlated (p-value < 0.05). VR engagement significantly negatively impacted overall pain scores (coefficient = -0.45, -0.41; p-value < 0.05) and significantly positively impacted time thinking of pain (coefficient = 0.38, 0.32; p-value < 0.05). Younger patients had the highest expectations of VR helpfulness and need. VR game realism, fun, and engagement features were not statistically different between age groups and sexes. VR engagement and thinking of pain during burn dressing significantly positively affected self-reported pain (p-value < 0.05), suggesting an analgesic mechanism beyond distraction alone. Younger patients benefited more from VR than older patients.

Ganoderma tsuage promotes pain sensitivity in aging mice

Advances in modern medicine have extended human life expectancy, leading to a world with a gradually aging society. Aging refers to a natural decline in the physiological functions of a species over time, such as reduced pain sensitivity and reaction speed. Healthy-level physiological pain serves as a warning signal to the body, helping to avoid noxious stimuli. Physiological pain sensitivity gradually decreases in the elderly, increasing the risk of injury. Therefore, geriatric health care receives growing attention, potentially improving the health status and life quality of the elderly, further reducing medical burden. Health food is a geriatric healthcare choice for the elderly with Ganoderma tsuage (GT), a Reishi type, as the main product in the market. GT contains polysaccharides, triterpenoids, adenosine, immunoregulatory proteins, and other components, including anticancer, blood sugar regulating, antioxidation, antibacterial, antivirus, and liver and stomach damage protective agents. However, its pain perception-related effects remain elusive. This study thus aimed at addressing whether GT could prevent pain sensitivity reduction in the elderly. We used a galactose-induced animal model for aging to evaluate whether GT could maintain pain sensitivity in aging mice undergoing formalin pain test, hot water test, and tail flexes. Our results demonstrated that GT significantly improved the sensitivity and reaction speed to pain in the hot water, hot plate, and formalin tests compared with the control. Therefore, our animal study positions GT as a promising compound for pain sensitivity maintenance during aging.

Mindful attention is inversely associated with pain via mediation by psychological distress in orthopedic patients

BACKGROUND

Orthopedic patients report pain as their main symptom complaint. Subjective pain experience is correlated with self-reported psychological state, such as distress.

PURPOSE

This study tests whether scores from a measure of mindful attention are associated with subjective pain levels and whether psychological distress scores function as a mediation path.

METHODS

During routine visits to a single orthopedic clinic in East Los Angeles, California, 525 patients were recruited to participate in the study. Participants reported on measures of pain (Universal Pain Assessment Tool [UPAT]), mindful attention (Five-Facet Mindfulness Questionnaire [FFMQ]), and psychological distress (Depression, Anxiety, Stress Scale [DASS]). We used Pearson correlations to examine relationships between FFMQ and UPAT scores and mediation analyses to test indirect effects of DASS scores as a mediation path.

RESULTS

The average age of the sample was 54 years (range 18-98 years), 61% were male, and 64% were non-Hispanic White individuals. The locations of injury were the shoulder (72%), elbow (21%), and clavicle or wrist (7%). Ninety-one percent reported mild or greater pain in the prior 2 weeks (mean = 4.2 ± 2.5, range 0-10), and 49% reported mild or more severe distress symptoms (DASS: 13.0 ± 11.5). FFMQ scores inversely predicted UPAT scores (β = -0.22, P < .01), mediated through DASS scores. DASS subscale scores for depression (β = -0.10, P = .02) and stress (β = -0.08, P = .04) but not anxiety (β = -0.03, P = .33) produced significant indirect effects. FFMQ acting-with-awareness and non-judging subscales had the largest effect on depression and stress DASS subscale scores.

CONCLUSIONS

We find statistical support to suggest that distress-particularly depressed mood and stress-mediates the association between mindful attention and pain intensity among orthopedic patients. A disposition of mindful attention might counter distress ailments that exacerbate subjective pain, and this has possible implications for mindfulness training interventions offered to orthopedic patients.

Adversity type and timing predict temporal summation of pain in African-American adults

African Americans are disproportionately exposed to adversity across the lifespan, which includes both stressful and traumatic events. Adversity, in turn, is associated with alterations in pain responsiveness. Racial differences in pain responsiveness among healthy adults are well established. However, the extent to which adversity type and timing are associated with alterations in pain responsiveness among healthy African-American adults is not well understood. The present study included 160 healthy African-American adults (98 women), ages 18 to 45. Outcome measures included pain tolerance and temporal summation of pain to evoked thermal pain. Composite scores were created for early-life adversity (childhood trauma, family adversity) and recent adversity (perceived stress, chronic stress burden). A measure of lifetime racial discrimination was also included. Higher levels of recent adversity were associated with higher temporal summation of pain, controlling for gender, age, and education. Neither early-life adversity nor lifetime racial discrimination were associated with temporal summation of pain. The present findings suggest that heightened temporal summation of pain among healthy African-American adults is associated with exposure to recent adversity events. Improved understanding of how recent adversity contributes to heightened temporal summation of pain in African Americans could help to mitigate racial disparities in pain experiences by identifying at-risk individuals who could benefit from early interventions.

The impact of sleep disturbance on pain perception: A systematic review examining the moderating effect of sex and age

Females have increased pain sensitivity and are more vulnerable to chronic pain conditions. Sleep disturbances are comorbid with chronic pain and exacerbate pain symptoms. Different types of sleep disturbance affect pain perception distinctly, but it is not clear if these effects are equal in men and women. This systematic review investigated potential differences in how sleep disturbance affects pain in males and females. We searched EBSCO, MEDLINE, Psych INFO, Science Direct, and Web of Science from January 2001 to November 2022 and found 38 studies with 978 participants. Separate random-effects models were used to estimate the pooled effect sizes based on standardized mean differences (SMDs) of experimental sleep disturbance paradigms on various pain outcomes. Sex moderated the effect of sleep disturbance on pain facilitation (SMD = 0.13; 95%CI: 0.004 to 0.022; p=.009) and pain inhibition (SMD = 0.033; 95%CI: 0.011 to 0.054; p=.005), with increased facilitation and decreased inhibition in females, but the opposite effect in males. Further, age moderated the effects of total sleep deprivation (SMD = -0.194; 95%CI -0.328 to -0.060; p=.008) on pain sensitivity and fragmented sleep (SMD = -0.110; 95%CI: 0.148 to -0.072; p<.001) on pain threshold. While the moderating effect of sex and age on the sleep-pain relationship was small, these factors need to be considered in future sleep-pain research.

Insulin syringe for anesthesia in ptosis surgery: a randomized, fellow eye-controlled clinical study

PURPOSE

Unlike ordinary 30-gauge needles, insulin syringe needles are thinner and shorter and have a comparatively blunt tip. Therefore, insulin syringes may reduce injection discomfort, bleeding, and edema by minimizing tissue damage and vascular penetration. This study aimed to evaluate the potential benefits of using insulin syringes for local anesthesia in ptosis surgery.

METHODS

This randomized, fellow eye-controlled study included 60 patients (120 eyelids), conducted at a university-based hospital. An insulin syringe was used on one eyelid, and a conventional 30-gauge needle was used on the other. Patients were instructed to score pain in both eyelids using a visual analog scale (VAS) ranging from 0 (no pain) to 10 (unbearable pain). Ten minutes after the injection, two observers scored degrees of hemorrhage and edema in both eyelids on five- and four-pointing grading scales (0-4 and 0-3) for each value, and the average score between the two observers was calculated and compared.

RESULTS

The VAS score was 5.17 in the insulin syringe group and 5.35 in the 30-gauge needle group (p = 0.282). Ten minutes after the anesthesia, the median hemorrhage scores were 1.00 and 1.75 (p = 0.010), and the median eyelid edema scores were 1.25 and 2.00 (p = 0.007) in the insulin syringe and 30-gauge needle groups, respectively (Fig. 1).

CONCLUSION

Injecting local anesthesia using an insulin syringe significantly reduces hemorrhage and eyelid edema, but not injection pain, before skin incision. Insulin syringes are useful in patients at high risk of bleeding because they can reduce the penetrative tissue damage caused by needle insertion.

Racial Differences in Head Pain and Other Pain-Related Outcomes After Mild Traumatic Brain Injury

Recent research suggests that mild traumatic brain injury (TBI) may exert deleterious effects on endogenous pain modulatory function, potentially underlying the elevated risk for persistent headaches following injury. Accumulating research also shows race differences in clinical and experimental pain, with African Americans (AA) generally reporting more severe pain, worse pain modulation, and greater pain sensitivity compared with Caucasians. However, race differences in pain-related outcomes following mild TBI have rarely been studied. The purpose of this study was to explore race differences in endogenous pain modulation, pain sensitivity, headache pain, and psychological factors among AA and Caucasian individuals with mild TBI in the first month following injury compared with healthy controls and across time. Patients with mild TBI were recruited from local emergency department trauma centers. Sixty-three participants with mild TBI (AAs: n = 23, Caucasians: n = 40) enrolled in this study and completed study sessions at 1-2 weeks and 1-month post-injury. Forty-one mild-TBI-free control participants (AAs: n = 11, Caucasians: n = 30), matched on age and sex, completed one study session. Assessments included a Headache Survey, Pain Catastrophizing Scale, Center for Epidemiological Studies-Depression Scale (CES-D), and quantitative sensory testing (QST) to measure endogenous pain modulatory function. QST included conditioned pain modulation (CPM) to measure endogenous pain inhibitory function and temporal summation (TS) of pain and pressure pain thresholds (PPTs) of the head to measure pain sensitization and sensitivity. Two-way analysis of variance (ANOVA) was used to determine whether the outcome measures differed as a function of race, mild TBI, and time. Mediation analysis was used to explore potential mediators for the race differences in headache pain intensity. The results showed that AA participants with mild TBI reported significantly greater headache pain and pain catastrophizing and exhibited higher pain sensitivity and worse pain modulation on QST compared with Caucasian participants with mild TBI. These same race differences were not observed among the healthy TBI-free control sample. The mediation analyses showed complete mediation for the relation between race and headache pain intensity by pain catastrophizing at 1-2 weeks and 1-month post-injury. Overall, the results of this study suggest that AAs compared with Caucasians are characterized by psychological and pain modulatory profiles following mild TBI that could increase the risk for the development of intense and persistent headaches following injury.

Spatial summation of thermal sensitivity is limited to small areas: Comparisons of the forehead, forearm, abdomen, and foot

The purpose of the present study was to examine if spatial summation in thermal sensitivity exists when stimulating areas larger than about 1% of body surface area (BSA) (approximately 200 cm2). We hypothesized that spatial summation would exist within a limited area and the effect would be insignificant for over the 1%BSA. Fifteen young males participated in this study and we measured their warmth and hot sensation thresholds on the four body regions (the forehead, forearm, abdomen, and instep) using the three sizes of radiant film heaters (10 × 10, 15 × 15, and 20 × 20 cm2 heating film area). The heating panel was kept at a distance of 10 cm from the skin and the surface temperature of the heating panel increased by 1 °C·s-1. The results showed that warmth and hot sensation thresholds were higher for the 100 cm2 condition than the 225 or 400 cm2 conditions (P < 0.05), but no differences were found between the 225 and 400 cm2 conditions. Secondly, the instep was most insensitive to the gradual increase of radiant heat among the four body regions for all three stimulating film sizes, even though the hot threshold was lowest for the instep because the initial foot temperature was lower than other skin temperatures. In summary, spatial summation in thermal sensitivity was found for the 100 and 225 cm 2 conditions, but not for the 225 and 400 cm2 conditions. These results suggest that spatial summation exists but limited to small stimulating areas, smaller than approximately 1% BSA.

The effects of high-definition transcranial direct current stimulation on pain modulation and stress-induced hyperalgesia

Background

The dorsolateral prefrontal cortex (DLPFC) has been implicated in the modulation of pain-related signals. Given this involvement, manipulation of the DLPFC through transcranial direct current stimulation (tDCS) may influence internal pain modulation and decrease pain sensitivity. Acute stress is also thought to affect pain, with increased pain sensitivity observed following the presentation of an acute stressor.

Methods

A total of 40 healthy adults (50% male), ranging in age from 19 to 28 years (M = 22.13, SD = 1.92), were randomly allocated to one of two stimulation conditions (active and sham). High-definition tDCS (HD-tDCS) was applied for 10 min at 2 mA, with the anode placed over the left DLPFC. Stress was induced after HD-tDCS administration using a modified version of the Trier Social Stress Test. Pain modulation and sensitivity were assessed through the conditioned pain modulation paradigm and pressure pain threshold measurements, respectively.

Results

Compared to sham stimulation, active stimulation produced a significant increase in pain modulation capacity. No significant change in pain sensitivity and stress-induced hyperalgesia was observed following active tDCS.

Conclusion

This research shows novel evidence that anodal HD-tDCS over the DLPFC significantly enhances pain modulation. However, HD-tDCS had no effect on pain sensitivity or stress-induced hyperalgesia. The observed effect on pain modulation after a single dose of HD-tDCS over the DLPFC is a novel finding that informs further research into the utility of HD-tDCS in the treatment of chronic pain by presenting the DLPFC as an alternative target site for tDCS-induced analgesia.

Predictors of Catheter-Related Bladder Discomfort After Surgery: A Literature Review

Background

Indwelling bladder catheters are routinely used in clinical practice. Patients may experience postoperative indwelling catheter-related bladder discomfort (CRBD). This study aimed to perform a literature review to identify predictors of postoperative CRBD.

Methods

We searched PubMed for relevant articles published between 2000 and 2020 using the search items "CRBD", "catheter-related bladder discomfort", and "prediction". Additionally, we searched for articles that matched the research objectives from the references of the extracted articles. We included only prospective observational studies involving human participants and excluded interventional studies, observational studies that did not report sample sizes, or observational studies that did not research on predictors of CRBD. We narrowed our search to the keyword "prediction" and found five references. We selected five studies that met the objectives of the study as the target literature.

Results

Using the keywords "CRBD" and "catheter-related bladder discomfort", we identified 69 published articles. The results were narrowed down by the keyword "prediction", and five studies that recruited 1,147 patients remained. The predictors of CRBD can be divided into four factors: 1) patient factors; 2) surgical factors; 3) anesthesia factors; and 4) device and insertion technique factors.

Conclusion

Our study suggests that patients with predictors of CRBD should be closely monitored to reduce postoperative patient suffering, and their quality of life should be improved after anesthesia.

Elucidating factors contributing to disparities in pain-related experiences among adults with or at risk for knee osteoarthritis

Background and purpose

We and others have reported ethnic/race group differences in clinical pain, physical function, and experimental pain sensitivity. However, recent research indicates that with consideration for socioenvironmental factors, ethnicity/race differences become less or non-significant. Understanding of factors contributing to pain inequities are needed. Guided by the NIA and NIMHD Health Disparities Research Frameworks, we evaluate the contributions of environmental and behavioral factors on previously reported ethnic/race group differences in: (1) clinical pain, (2) physical function, and (3) experimental pain in individuals with knee pain.

Methods

Baseline data from Understanding of Pain and Limitations in Osteoarthritis Disease (UPLOAD) and UPLOAD-2 studies were analyzed. Participants were adults 45 to 85 years old who self-reported as non-Hispanic white (NHW) or black (NHB) with knee pain. A health assessment and quantitative sensory testing were completed. Sociodemographics, environmental, health, clinical and experimental pain, and physical functioning measures were included in nested regressions.

Results

Pooled data from 468 individuals, 57 ± 8 years of age, 63% women, and 53% NHB adults. As NHB adults were younger and reported greater socioenvironmental risk than the NHW adults, the term sociodemographic groups is used. With inclusion of recognized environmental and behavioral variables, sociodemographic groups remained a significant predictor accounting for <5% of the variance in clinical pain and physical function and <10% of variance in experimental pain.

Conclusion

The incorporation of environmental and behavioral factors reduced relationships between sociodemographic groups and pain-related outcomes. Pain sites, BMI, and income were significant predictors across multiple models. The current study adds to a body of research on the complex array of factors contributing to disparities in pain-related outcomes.

Enhanced pain sensitivity in obese patients with obstructive sleep apnoea syndrome is partially reverted by treatment: An exploratory study

BACKGROUND

Obesity is frequently associated with obstructive sleep apnoea syndrome (OSA) and chronic pain. OSA as well as continuous positive airway pressure (CPAP) treatment may modulate the pain perception threshold (PT) in patients with obesity.

METHODS

In this prospective, longitudinal study, all patients admitted for obesity assessment were screened for OSA by nocturnal polygraphy (SOMNOcheck^® , IAH ≥10) and performed mechanical (Von Frey electronic device) and electrical (PainMatcher^® ) pain tests. Those with severe OSA were retested for PT 1 month after initiation of CPAP therapy. Newly diagnosed patients with severe OSA (hypopnea apnoea index >30) have been offered to start CPAP treatment.

RESULTS

Among 85 patients, there were 27 OSA patients, aged between 40 ± 13.2 years with a BMI of 42 ± 7.2 kg/m² . Severe OSA patients (N = 11) showed a lower PT than non-OSA patients (N = 58) during mechanical (177 ± 120 vs. 328 ± 136 g, p < 0.01) and electrical methods (7.4 ± 6.4 vs. 12.9 ± 6.7 stimulation duration steps; p = 0.03). In the severe OSA group (N = 7), an increased PT was observed 1 month after CPAP treatment during mechanical pain testing (298 ± 69 vs. 259 ± 68 g, p < 0.05), but not during electrical pain testing (11.5 ± 3.0 vs. 12.4 ± 3.8 stimulation duration steps, p = 0.50).

CONCLUSION

In patients with obesity, this exploratory study showed that the presence of an OSA is associated with a decreased PT, whereas implantation of a CPAP device tends to normalize pain perception.

PAQR8 and PAQR9 expression is altered in the ventral tegmental area of aged rats infected with varicella zoster virus

Infection with varicella zoster virus (VZV) results in chicken pox and reactivation of VZV results in herpes zoster (HZ) or what is often referred to as shingles. Patients with HZ experience decreased motivation and increased emotional distress consistent with functions of the ventral tegmental area (VTA) of the brain. In addition, activity within the ventral tegmental area is altered in patients with HZ. HZ primarily affects individuals that are older and the VTA changes with age. To begin to determine if the VTA has a role in HZ symptoms, a screen of 10,000 genes within the VTA in young and old male rats was completed after injecting the whisker pad with VZV. The two genes that had maximal change were membrane progesterone receptors PAQR8 (mPRβ) and PAQR9 (mPRε). Neurons and non-neuronal cells expressed both PAQR8 and PAQR9. PAQR8 and PAQR9 protein expression was significantly reduced after VZV injection of young males. In old rats PAQR9 protein expression was significantly increased after VZV injection and PAQR9 protein expression was reduced in aged male rats versus young rats. Consistent with previous results, pain significantly increased after VZV injection of the whisker pad and aged animals showed significantly more pain than young animals. Our data suggests that PAQR8 and PAQR9 expression is altered by VZV injection and that these changes are affected by age.

Pain and aging: A unique challenge in neuroinflammation and behavior

Chronic pain is one of the most common, costly, and potentially debilitating health issues facing older adults, with attributable costs exceeding $600 billion annually. The prevalence of pain in humans increases with advancing age. Yet, the contributions of sex differences, age-related chronic inflammation, and changes in neuroplasticity to the overall experience of pain are less clear, given that opposing processes in aging interact. This review article examines and summarizes pre-clinical research and clinical data on chronic pain among older adults to identify knowledge gaps and provide the base for future research and clinical practice. We provide evidence to suggest that neurodegenerative conditions engender a loss of neural plasticity involved in pain response, whereas low-grade inflammation in aging increases CNS sensitization but decreases PNS sensitivity. Insights from preclinical studies are needed to answer mechanistic questions. However, the selection of appropriate aging models presents a challenge that has resulted in conflicting data regarding pain processing and behavioral outcomes that are difficult to translate to humans.

Influence of genetic variants on remifentanil sensitivity in Chinese women

WHAT IS KNOWN AND OBJECTIVE

Significant individual differences have been observed in pain sensitivity and analgesic effect of opioids. Previous studies have shown that genetic factors contributed to analgesics requirement obviously. Therefore, we investigated the role of genetic polymorphisms in the sensitivity to the analgesic effect of remifentanil in this study.

METHODS

One hundred thirty-seven patients undergoing gynaecological surgery were observed. Before procedures, we measured the basal pain threshold of each patient, including the pressure pain threshold and pressure pain tolerance threshold. Subsequently, patients received a continuous remifentanil infusion for 15 min at a constant rate of 0.2 μg/(kg min). The pain thresholds were measured again after the remifentanil infusion. Moreover, respiratory depression was estimated using oxygen saturation during infusion. DNA was extracted from peripheral venous blood and genotyped using SNaPshot technology.

RESULTS AND DISCUSSION

Polymorphisms were found in genes associated with the individual variation in analgesia. Participants carrying OPRM1 rs9397685 AA, ADRB1 rs1801253 CC, and GCH1 rs8007267 CC polymorphisms showed higher sensitivity to analgesic effect induced by remifentanil, and the participants carrying the OPRD1 rs2234918 TT showed lower sensitivity to remifentanil-related respiratory depression. Moreover, individual susceptibility to remifentanil increases with age.

WHAT IS NEW AND CONCLUSION

Gene variation in OPRM1 rs9397685 AA, ADRB1 rs1801253 CC, GCH1 rs8007267 CC, and OPRD1 rs2234918 TT were related to the conspicuous interindividual differences in the analgesia and respiratory depression of remifentanil, mainly by affecting the target protein receptors and relative metabolic enzymes.

Opportunities and challenges of pain-related myocardial ischemia-reperfusion injury

Pain is one of the most serious problems plaguing human health today. Pain is not an independent pathophysiological condition and is associated with a high impact on elevated disability and organ dysfunction. Several lines of evidence suggested the associations of pain with cardiovascular diseases, especially myocardial ischemia-reperfusion (I/R) injury, while the role of pain in I/R injury and related mechanisms are not yet comprehensively assessed. In this review, we attempted to explore the role of pain in myocardial I/R injury, and we concluded that acute pain protects myocardial ischemia-reperfusion injury and chronic pain aggravates cardiac ischemia-reperfusion injury. In addition, the construction of different pain models and animal models commonly used to study the role of pain in myocardial I/R injury were discussed in detail, and the potential mechanism of pain-related myocardial I/R injury was summarized. Finally, the future research direction was prospected. That is, the remote regulation of pain to cardiac function requires peripheral pain signals to be transmitted from the peripheral to the cardiac autonomic nervous system, which then affects autonomic innervation during cardiac ischemia-reperfusion injury and finally affects the cardiac function.

Experimental Pain Phenotype Profiles in Community-dwelling Older Adults

OBJECTIVES

Pain sensitivity and the brain structure are critical in modulating pain and may contribute to the maintenance of pain in older adults. However, a paucity of evidence exists investigating the link between pain sensitivity and brain morphometry in older adults. The purpose of the study was to identify pain sensitivity profiles in healthy, community-dwelling older adults using a multimodal quantitative sensory testing protocol and to differentiate profiles based on brain morphometry.

MATERIALS AND METHODS

This study was a secondary analysis of the Neuromodulatory Examination of Pain and Mobility Across the Lifespan (NEPAL) study. Participants completed demographic and psychological questionnaires, quantitative sensory testing, and a neuroimaging session. A Principal Component Analysis with Varimax rotation followed by hierarchical cluster analysis identified 4 pain sensitivity clusters (the "pain clusters").

RESULTS

Sixty-two older adults ranging from 60 to 94 years old without a specific pain condition (mean [SD] age=71.44 [6.69] y, 66.1% female) were analyzed. Four pain clusters were identified characterized by (1) thermal pain insensitivity; (2) high pinprick pain ratings and pressure pain insensitivity; (3) high thermal pain ratings and high temporal summation; and (4) thermal pain sensitivity, low thermal pain ratings, and low mechanical temporal summation. Sex differences were observed between pain clusters. Pain clusters 2 and 4 were distinguished by differences in the brain cortical volume in the parieto-occipital region.

DISCUSSION

While sufficient evidence exists demonstrating pain sensitivity profiles in younger individuals and in those with chronic pain conditions, the finding that subgroups of experimental pain sensitivity also exist in healthy older adults is novel. Identifying these factors in older adults may help differentiate the underlying mechanisms contributing to pain and aging.

High Prevalence of Pain Sensitization in Knee Osteoarthritis: A Meta-Analysis with Meta-Regression

OBJECTIVE

The aim of this meta-analysis was to study the evidence on pain sensitization in knee osteoarthritis (OA), providing a quantitative synthesis of its prevalence and impact. Factors associated with pain sensitization were also investigated.

METHODS

Meta-analysis; PubMed (MEDLINE), Cochrane Central Register (CENTRAL), and Web of Science were searched on February 2021. Level I to level IV studies evaluating the presence of pain sensitization in patients with symptomatic knee OA, documented through a validated method (questionnaires or quantitative sensory testing), were included. The primary outcome was the prevalence of pain sensitization. Factors influencing the prevalence were also evaluated, as well as differences in terms of pain thresholds between knee OA patients and healthy controls.

RESULTS

Fifty-three articles including 7,117 patients were included. The meta-analysis of proportion documented a prevalence of pain sensitization of 20% (95% confidence interval [CI] = 16%-26%) with a significant heterogeneity of results (I² = 89%, P < 0.001). The diagnostic tool used was the main factor influencing the documented prevalence of pain sensitization (P = 0.01). Knee OA patients presented higher pain sensitivity compared with healthy controls, both in terms of local pressure pain threshold (standardized mean difference [SMD] = -1.00, 95% CI = -1.67 to -0.32, P = 0.007) and distant pressure pain threshold (SMD = -0.54, 95% CI = -0.76 to -0.31, P < 0.001).

CONCLUSIONS

Knee OA pain presents features that are consistent with a significant degree of pain sensitization. There is a high heterogeneity in the reported results, mainly based on the diagnostic tool used. The identification of the best methods to detect pain sensitization is warranted to correctly evaluate and manage symptoms of patients affected by knee OA.

REGISTRATION

PROSPERO CRD42019123347.

Stress-induced analgesia: an evaluation of effects on temporal summation of pain and the role of endogenous opioid mechanisms

Acute stress reduced the initial pain rating in a temporal summation protocol via nonopioid mechanisms but did not affect temporal summation slope, an indicator of central sensitization.

Introduction:

Objectives:

Methods:

Results:

Conclusions:

Racial Differences in Pain, Nutrition, and Oxidative Stress

Investigating the disproportionate rates of chronic pain and their related comorbidities between Black and non-Hispanic White (White) individuals is a growing area of interest, both in the healthcare community and in general society. Researchers have identified racial differences in chronic pain prevalence and severity, but still very little is known about the mechanisms underlying them. Current explanations for these differences have primarily focused on socioeconomic status and unequal healthcare between races as causal factors. Whereas these factors are informative, a racial gap still exists between Black and White individuals when these factors are controlled for. One potential cause of this racial gap in chronic pain is the differences in nutrition and dietary intake between groups. Certain foods play a key role in the inflammatory and oxidative stress pathways in the human body and could potentially influence the severity of the pain experience. Here, we review the previous literature on the surrounding topics and propose a potential mechanism to explain racial differences in the chronic pain population, based on established racial differences in diet and oxidative stress.

The Effect of the Dreamer Spiritual Therapies on Saliva Cortisol Hormone and Pain Score Patients in the Intensive Care Unit: A True-experimental Study

BACKGROUND: Patients’ conditions can worsen if stress and pain are not appropriately managed. Conventional therapy ignores psychological and spiritual aspects. Both influence the body’s response to various stimuli. AIM: This study aimed to assess how Dreamer’s spiritual therapy can affect the cortisol and pain in the intensive care unit (ICU) patients. METHODS: It involved 86 ICU patients in a true-experimental study. Respondents were divided into the intervention and the control group randomly. The intervention group received Dreamer spiritual therapy (DST) for 30 min but not for the control group. Saliva samples and pain scores were taken from both groups before and after treatment. The comparison of two groups cortisol decreases using Wilcoxon test. Differences in pre- and post-pain scores in each group were analyzed using paired t-test. RESULTS: According to Levene’s test, the two groups were homogeneous (p > 0.05). The Wilcoxon test revealed a statistically significant difference in cortisol level reduction between the intervention (3.88 ng/mL) and control (3.82 ng/ml) groups (p = 0.024), with a large effect size (Cohen’s d value = 59.5). The paired t-test revealed a statistically significant decrease in the intervention group’s pain score from 2.6 to 1.95 (p = 0.001), with a moderate effect size (Cohen’s d value = 0.49). The control group’s pain score did not significantly decrease (p = 0.75). CONCLUSIONS: A DST is effective in reducing salivary cortisol levels and pain scores of ICU patients.

Predictors of Chronic Postsurgical Pain in Elderly Patients Undergoing Hip Arthroplasty: A Multi-Center Retrospective Cohort Study

Background

Identifying patients at high risk of developing chronic postsurgical pain (CPSP) is of extreme importance in order to help launch appropriate therapeutic strategies and intensive initiation of pain management.

Aim

In this study, we aimed to conduct a multi-center retrospective cohort study to establish a prognostic model and a nomogram to predict the risks of CPSP in elderly patients who underwent hip arthroplasty at 6 months postoperatively.

Methods

We collected data from 736 patients aged >65 years who had undergone hip arthroplasty from October 1, 2016 to September, 30, 2018 at multiple tertiary referral centers in Guangzhou, China. All data were randomly stratified into a training set and a testing set at a ratio of 8:2. Data were analyzed via multiple logistic regression analysis with receiver operating characteristic (ROC) curves and areas under the curve. This model was further validated by estimating calibration and discrimination. A nomogram was ultimately developed.

Results

A total of 736 eligible patients were enrolled, 27.20% of whom developed CPSP within 6 months postoperatively. Preoperative pain in the surgical area (OR=2.456, 95% CI:1.814–3.327, P<0.001), preoperative depression state (OR=1.256, 95% CI:1.146–1.378, P<0.001), surgical type (OR=7.138, 95% CI:3.548–14.364, P<0.001), acute postoperative numerical rating scale score (OR=5.537, 95% CI:3.607–8.499, P<0.001) and analgesic type (patient-controlled epidural analgesia: OR=0.129, 95% CI:0.055–0.299, P<0.001; patient-controlled intravenous analgesia: OR=0.033, 95% CI:0.011–0.097, P<0.001) were identified as independent significant factors associated with CPSP. A prognostic model was established and further validated. An ROC curve confirmed the predictive ability of this model with a high sensitivity value of 92.12% (95% CI:86.90–95.74) and specificity value of 91.72% (95% CI:88.77–94.11). A nomogram was developed to simplify the use of the predictive model in clinical practice.

Conclusion

This prognostic model could be of great value in clinical practice, serving as the basis for early personalized analgesic management of elderly patients undergoing hip arthroplasty.

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Does Resiliency Mediate the Association of Psychological Adaptability with Limitations and Pain Intensity after Upper Extremity Trauma?

BACKGROUND

Given the influence of psychosocial factors on musculoskeletal symptoms and limitations, this study assessed if the ability of resilience (an individual's ability to adapt under stress) mediates the association of psychological adaptability with magnitude of physical limitations and pain intensity during recovery from an upper extremity injury.

METHODS

A total of 107 patients were enrolled in this prospective, longitudinal, observational cohort study. Patients completed the Patient-Reported Outcomes Measurement Information System Physical Function (PROMIS PF), an 11-point ordinal measure of pain intensity, the Brief Resilience Scale (BRS), and the Psychological Adaptation Scale (PAS). We used structural equation modeling to assess the mediation effect by resiliency and psychological adaptability on patient-reported disability and pain at initial assessment and after three months.

RESULTS

PAS and BRS were not independently associated with PROMIS PF or pain intensity at enrollment or after three months, so it was not possible to assess if resiliency mediated the association of psychological adaptability with physical function or pain. There were no factors independently associated with resilience.

CONCLUSION

General measures of psychological adaptability and resiliency do not correlate with symptoms and limitations as well as specific measures of adaptiveness in response to nociception.

Is Open Reduction Internal Fixation Using Titanium Plates in the Mandible as Successful as We Think?

ABSTRACT

Titanium plats are the gold-standard for fracture fixation. Titanium is considered biocompatible, corrosion resistant with an elasticity-modulus closest to bone. Nonetheless, titanium plates are not always as inherent as hoped. The authors investigated morbidity associated with titanium plates in mandibular fractures. A retrospective study of mandibular fractures treated between 2000 and 2018 using internal-fixation was conducted. Data included age, gender, complications, and location. Predictor-variable was location. Outcome-variable was plate removal. A total of 571 patients were included, 107 resulted in plate removal (18.7%). Body was the most prevalent location of fracture (29.3%). Symphysis/para-symphysis showed the highest removal rate (24.1%), followed by body and angle (21.3/19.8%). A total of 23.4% of double-plating cases resulted in plate removal, upper-border in 15% and lower-border in 8.8%, all reconstruction-plates. Exposure was the most frequent complication leading to removal. Although titanium plates are the gold standard, almost every fifth patient returns for plate removal. Age-distribution emphasizing 41 to 50 with decrease towards extremities may imply better healing in the young and soft-tissue elasticity and less complaints in the elderly. Significantly more complications in double-plating compared to lower border suggests proximity to the oral-cavity as a risk-factor for removal. Complication rates and patterns are not negligible and perhaps should encourage clinicians to consider using biodegradable-systems for upper-border plates.

Differences in myoelectric activity of the lumbar muscles between recurrent and chronic low back pain: a cross-sectional study

Background

Altered lower back muscle activity is proposed as a contributing factor to the reoccurrence and chronicity of low back pain (LBP). This study compared lumbar muscle activity during trunk extension in patients with continuous chronic LBP (CLBP), non-continuous CLBP, recurrent LBP (RLBP) and healthy subjects.

Methods

In 75 subjects (16 continuous CLBP, 15 non-continuous CLBP, 23 RLBP, 21 healthy controls), surface electromyographic (EMG) activity of the lumbar erector spinae (ES), multifidus (MF), latissimus dorsi (LD) and gluteus maximus (GM) was recorded during the concentric, holding and eccentric phase of a modified Biering Sorenson exercise.

Results

Continuous CLBP patients showed higher EMG activity in the ES and MF muscles compared to healthy controls in the concentric (p = 0.011; p = 0.009 respectively) and the holding phase (p = 0.015; p = 0.013). Higher EMG activity was observed in continuous CLBP compared to RLBP in the ES and MF muscles in the holding phase (p = 0.035; p = 0.037), and in the MF in the concentric phase (p = 0.046), but not in the ES (p = 0.062). No differences in muscle activity were established in either the concentric, holding, and eccentric phase for the LD and GM muscles. No differences were found between non-continuous CLBP and the other groups.

Conclusions

An enhanced muscle activity of the lumbar muscles during the concentric and holding phase was observed during trunk extension in patients with continuous CLBP compared to patients with RLBP and healthy subjects. No differences between groups are present in the GM and LD muscles during concentric and holding phases and for any muscle in the eccentric phase.

Chronic Pain in the Elderly: Mechanisms and Distinctive Features

Background: Chronic pain is a major issue affecting more than 50% of the older population and up to 80% of nursing homes residents. Research on pain in the elderly focuses mainly on the development of clinical tools to assess pain in patients with dementia and cognitive impairment or on the efficacy and tolerability of medications. In this review, we searched for evidence of specific pain mechanisms or modifications in pain signals processing either at the cellular level or in the central nervous system. Methods: Narrative review. Results: Investigation on pain sensitivity led to conflicting results, with some studies indicating a modest decrease in age-related pain sensitivity, while other researchers found a reduced pain threshold for pressure stimuli. Areas of the brain involved in pain perception and analgesia are susceptible to pathological changes such as gliosis and neuronal death and the effectiveness of descending pain inhibitory mechanisms, particularly their endogenous opioid component, also appears to deteriorate with advancing age. Hyperalgesia is more common at older age and recovery from peripheral nerve injury appears to be delayed. In addition, peripheral nociceptors may contribute minimally to pain sensation at either acute or chronic time points in aged populations. Conclusions: Elderly subjects appear to be more susceptible to prolonged pain development, and medications acting on peripheral sensitization are less efficient. Pathologic changes in the central nervous system are responsible for different pain processing and response to treatment. Specific guidelines focusing on specific pathophysiological changes in the elderly are needed to ensure adequate treatment of chronic pain conditions.

Age Differences in Multimodal Quantitative Sensory Testing and Associations With Brain Volume

BACKGROUND AND OBJECTIVES

Somatosensory function is critical for successful aging. Prior studies have shown declines in somatosensory function with age; however, this may be affected by testing site, modality, and biobehavioral factors. While somatosensory function declines are associated with peripheral nervous system degradation, little is known regarding correlates with the central nervous system and brain structure in particular. The objectives of this study were to examine age-related declines in somatosensory function using innocuous and noxious stimuli, across 2 anatomical testing sites, with considerations for affect and cognitive function, and associations between somatosensory function and brain structure in older adults.

RESEARCH DESIGN AND METHODS

A cross-sectional analysis included 84 "younger" (n = 22, age range: 19-24 years) and "older" (n = 62, age range: 60-94 years) healthy adults who participated in the Neuromodulatory Examination of Pain and Mobility Across the Lifespan study. Participants were assessed on measures of somatosensory function (quantitative sensory testing), at 2 sites (metatarsal and thenar) using standardized procedures, and completed cognitive and psychological function measures and structural magnetic resonance imaging.

RESULTS

Significant age × test site interaction effects were observed for warmth detection (p = .018,η p 2 = 0.10) and heat pain thresholds (p = .014,η p 2 = 0.12). Main age effects were observed for mechanical, vibratory, cold, and warmth detection thresholds (ps < .05), with older adults displaying a loss of sensory function. Significant associations between somatosensory function and brain gray matter structure emerged in the right occipital region, the right temporal region, and the left pericallosum.

DISCUSSION AND IMPLICATIONS

Our findings indicate healthy older adults display alterations in sensory responses to innocuous and noxious stimuli compared to younger adults and, furthermore, these alterations are uniquely affected by anatomical site. These findings suggest a nonuniform decline in somatosensation in older adults, which may represent peripheral and central nervous system alterations part of aging processes.

Advancing our understanding of neuropathic pain in diabetes mellitus using conditioned pain modulation: further considerations for age and testing site

ABSTRACT

Neuropathy is common among individuals with diabetes mellitus, and is associated with decreased quality of life, greater comorbidity, and substantial economic burden. However, the mechanisms underlying painful diabetic polyneuropathy has yet to be fully elucidated. While it is recognized that diabetic polyneuropathy places patients at a greater risk for developing neuropathic pain, it is still not clear why some individuals develop pain and others do not. Similar to other chronic pain conditions, painful diabetic neuropathy is likely driven by alterations in both the peripheral and central nervous system. Experimental conditioned pain modulation paradigms have contributed substantially to our current understanding of chronic pain across various disease states. In a new study, researchers have extended this work by examining the efficiency of conditioned pain modulation in patients with painful and non-painful diabetic polyneuropathy. Surprisingly, the results indicate individuals with painful neuropathy experience greater endogenous pain inhibition, which may seem counterintuitive at first blush. Here, we discuss potential explanations and directions for future research, including consideration for age effects, testing site, and disease type, with the goal of further advancing this important line of research.

Static and Dynamic Pain Sensitivity in Adults With Persistent Low Back Pain: Comparison to Healthy Controls and Associations With Movement-evoked Pain Versus Traditional Clinical Pain Measures

OBJECTIVES

Despite its impact, individual factors associated with persistent low back pain (LBP) remain poorly understood. This study investigated static and dynamic pain sensitivity in adults with persistent LBP versus pain-free controls; and investigated associations between pain sensitivity and 3 clinical pain measures: recalled, resting, and movement-evoked pain (MEP).

MATERIALS AND METHODS

A lifespan sample of 60 adults with persistent LBP and 30 age-matched/sex-matched controls completed 4 laboratory sessions. Static pain sensitivity (pressure pain threshold [PPT], heat pain threshold) and dynamic pain sensitivity (heat pain aftersensations [AS], temporal summation [TS] of second heat pain) were measured. Demographic and clinical factors collected were education, global cognition, and perceived health. Resting and recalled pain were measured via questionnaire, and MEP via the Back Performance Scale.

RESULTS

LBP participants demonstrated lower PPT remotely (hand; F1,84=5.34, P=0.024) and locally (low back; F1,84=9.55, P=0.003) and also had higher AS (F1,84=6.01, P=0.016). Neither static nor dynamic pain sensitivity were associated with recalled pain (P>0.05). However, static pain sensitivity (local PPT) explained an additional 9% variance in resting pain, while dynamic pain sensitivity (AS, TS) explained an additional 10% to 12% variance in MEP.

DISCUSSION

This study characterized pain sensitivity measures among individuals with persistent LBP and suggests static pain sensitivity plays a larger role in resting pain while dynamic pain sensitivity plays a larger role in MEP. Future studies will confirm these relationships and elucidate the extent to which changes in static or dynamic pain sensitivity predict or mediate clinical pain among adults with persistent LBP.

The Effect of Cold Therapy Applied to the Incision Area After Abdominal Surgery on Postoperative Pain and Analgesic Use

BACKGROUND

Cold therapy is one of the most common nonpharmacologic pain treatments. Despite the existence of many studies about cold therapy, few have examined the effects of cold therapy after abdominal surgery.

AIMS

The purpose of the study was to investigate the effect of cold therapy applied to the incision area after abdominal surgery on postoperative pain and analgesic use.

DESIGN

This study was a randomized controlled trial METHODS: The sample included 60 patients (30 control, 30 experimental) undergoing abdominal surgery. Researchers recorded information from a patient information form, a visual analogue scale (VAS), a pain evaluation form, and the vital signs recording form.

RESULTS

There was no statistically significant difference in pain level between the experimental and control groups as measured by VAS at postoperative hour 1 (p > .05). Furthermore, no statistically significant difference in VAS pain levels between groups was observed at postoperative hours 1, 2, and 8 prior to application of cold therapy (p > .05). Then, when cold therapy was applied at hours 1, 2 and 8, the pain level decreased significantly in the experimental group (p =.001). Pain also decreased in the control group between hours 1 and 8, but this decrease was not as great as that in the experimental group (p = .024).

CONCLUSIONS

Both groups had decreased pain levels, and the decrease in the experimental group was greater than in the control group but cold therapy had no statistically significant effect on analgesics use.

Within-session test-retest reliability of pressure pain threshold and mechanical temporal summation in healthy subjects

Objective

To determine the absolute and relative intra-rater within-session test-retest reliability of pressure pain threshold (PPT) and mechanical temporal summation of pain (TSP) at the low back and the forearm in healthy participants and to test the influence of the number and sequence of measurements on reliability metrics.

Methods

In 24 participants, three PPT and TSP measures were assessed at four sites (2 at the low back, 2 at the forearm) in two blocks of measurements separated by 20 minutes. The standard error of measurement, the minimal detectable change (MDC) and the intraclass correlation coefficient (ICC) were investigated for five different sequences of measurements (e.g. measurement 1, 1–2, 1-2-3).

Results

The MDC for the group (MDC_gr) for PPT ranged from 28.71 to 50.56 kPa across the sites tested, whereas MDC_gr for TSP varied from 0.33 to 0.57 out of 10 (numeric scale). Almost all ICC showed an excellent relative reliability (between 0.80 and 0.97), except when only the first measurement was considered (moderate). Although minimal differences in absolute PPT reliability were present between the different sequences, in general, using only the first measurement increase measurement error. Three TSP measures reduced the measurement error.

Discussion

We established that two measurements of PPT and three of TSP reduced the measurement error and demonstrated an excellent relative reliability. Our results could be used in future pain research to confirm the presence of true hypo/hyperalgesia for paradigms such as conditioned pain modulation or exercise-induced hypoalgesia, indicated by a change exceeding the measurement variability.

Experimental sleep disruption attenuates morphine analgesia: findings from a randomized trial and implications for the opioid abuse epidemic

Preclinical studies demonstrate that sleep disruption diminishes morphine analgesia and modulates reward processing. We sought to translate these preclinical findings to humans by examining whether sleep disruption alters morphine's analgesic and hedonic properties. We randomized 100 healthy adults to receive morphine versus placebo after two nights of undisturbed sleep (US) and two nights of forced awakening (FA) sleep disruption. Sleep conditions were counterbalanced, separated by a two-week washout. The morning after both sleep conditions, we tested cold pressor pain tolerance before and 40-min after double-blind injection of .08 mg/kg morphine or placebo. The primary outcome was the analgesia index, calculated as the change in cold pressor hand withdrawal latency (HWL) before and after drug injection. Secondary outcomes were ratings of feeling "high," drug "liking," and negative drug effects. We found a significant sleep condition by drug interaction on the analgesia index (95% CI - 0.57, - 0.001). After US, subjects receiving morphine demonstrated significantly longer HWL compared to placebo (95% CI 0.23, 0.65), but not after FA (95% CI - 0.05, 0.38). Morphine analgesia was diminished threefold under FA, relative to US. After FA, females (95% CI - 0.88, - 0.05), but not males (95% CI - 0.23, 0.72), reported decreased subjective "high" effects compared to US. After FA, females (95% CI 0.05, 0.27), but not males (95% CI - 0.10, 0.11), administered morphine reported increased negative drug effects compared to US. These data demonstrate that sleep disruption attenuates morphine analgesia in humans and suggest that sleep disturbed males may be at greatest risk for problematic opioid use.

Greater mechanical temporal summation of pain in Latinx-Americans and the role of adverse life experiences

Supplemental Digital Content is Available in the Text.

Latinx-Americans showed greater temporal summation, adversity, and adversity correlates relative to non-Hispanic Whites. Discrimination and lifespan social status change inversely related to summation for Latinx-Americans.

Introduction:

Adverse life experiences disproportionately impact Latinx-Americans and are related to greater chronic pain rates. However, little is known about how adversities interact with central pain mechanisms for the development of later pain among Latinx-Americans.

Objectives:

The current study examined the relationship between adverse life experiences (eg, trauma and ethnic discrimination) and correlates (eg, social status) with mechanical temporal summation of pain (a proxy measure of central sensitization) between pain-free U.S. native Latinx (n = 65) and non-Hispanic White (NHW) (n = 51) adults.

Methods:

Participants completed self-report adverse life experience and correlational measures regarding childhood and adulthood and a mechanical temporal summation protocol.

Results:

Relative to NHWs, Latinx-Americans reported experiencing significantly greater trauma, discrimination, and lower social status during childhood and adulthood, along with greater temporal summation. Contrary to hypotheses, recent and lifetime experiences of ethnic discrimination significantly correlated with less temporal summation among Latinx-Americans. Decreases in objective and subjective social status across the lifespan (childhood to present day) correlated with greater temporal summation for Latinx-Americans. However, r-to-z transformation analyses confirmed that significant adversity and social status correlations observed among the Latinx group did not significantly differ from NHW participants.

Conclusions:

The present findings highlight the complex association between adverse experiences, adverse experience risk factors, and pain for Latinx-Americans. Given the disproportion of experienced pain and adversity among Latinx-Americans, the current findings suggest that a better understanding of the unique adversities for this sample may help elucidate the mechanisms underlying the relationship between adversities, adversity correlates, and pain risk for Latinx-Americans.

Effects of Conditioned Pain Modulation on the Nociceptive Flexion Reflex in Healthy People: A Systematic Review

OBJECTIVES

The nociceptive flexion reflex (NFR) is a spinal reflex induced by painful stimuli resulting in a withdrawal response. Research has shown that the NFR is inhibited through endogenous pain inhibitory mechanisms, which can be assessed by conditioned pain modulation (CPM) paradigms. Although accumulating research suggests that the NFR can be affected by CPM, no clear overview of the current evidence exists. Therefore, the present review aimed at providing such a synthesis of the literature. In addition, the influence of personal factors on the CPM of the NFR was investigated.

MATERIALS AND METHODS

A systematic review was performed and reported following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Five electronic databases were searched to identify relevant articles. Retrieved articles were screened on eligibility using predefined inclusion criteria. Risk of bias was investigated according to the modified Newcastle-Ottawa Scale. Levels of evidence and strength of conclusion were assigned following the guidelines of the Dutch Institute for Healthcare Improvement.

RESULTS

Forty articles were included. There is some evidence that CPM produced by thermal or mechanical stimuli induces inhibitory effects on the NFR. However, inconclusive evidence exists with regard to the effect of electrical conditioning stimuli. While several personal factors do not affect CPM of the NFR, increased cognitive interference is associated with reduced NFR inhibition.

DISCUSSION

The present review demonstrates that certain types of nociceptive conditioning stimuli have the potential to depress, at the spinal level, nociceptive stimuli elicited from distant body regions. Although CPM of the NFR seems to be robust to the influence of several personal factors, it can be affected by cognitive influences.

[Predictors of catheter-related bladder discomfort]

INTRODUCTION

Establish a descriptive epidemiological profile of patients with Catheter Related Bladder Discomfort (CRBD) and identify its predictive factors.

MATERIAL AND METHOD

Between June 2019 and December 2019, 300 patients have been evaluated. Different parameters were taken into account including: sex, age, body mass index (BMI), historical health data, duration and indications of the urinary catheterization, type of the transurethral catheter used, lubrication of the catheter and the existence of CRBD. We grouped our patients according to the intensity of CRBD syndrome. The various factors likely to be correlated with the occurrence of CRBD were subject of a univariate then multivariate analysis.

RESULTS

300 patients were included. The average age was 49 years (133 men and 167 women). 68 patients (22.6%) had history of urinary catheterization. 19% of patients were catheterized for acute urinary retention, while 81% were catheterized before surgery. The average duration of the urinary catheterization was 2.5 days. 54% showed CRBD symptoms, including more than 92% on the first day of the urinary catheterization. The significant risk factors in multivariate analysis were: the caliber of the catheter ≥18 Fr, the absence of lubrication, laparotomy, age <50 years, Cesarean and urinary catheterization medical history.

CONCLUSION

This study identified various factors incriminated in the occurrence of CRBD. The role of the hospital practitioner is to prevent this syndrome by reducing predictive factors, particularly the technical ones.

LEVEL OF EVIDENCE

3.

Pain Bloc-R Alleviates Unresolved, Non-Pathological Aches and Discomfort in Healthy Adults—A Randomized, Double-Blind, Placebo-Controlled, Crossover Study

The lack of effective treatment for chronic discomfort without negative side effects highlights the need for alternative treatments. Pain Bloc-R is a natural health product composed of vitamins B₆, B₁₂, D, white willow bark extract, Angelica root extract, acetyl L-carnitine HCl, caffeine, L-theanine, Benfotiamine, and L-tetrahydropalmatine. The objective of this study was to compare the effects of Pain Bloc-R, acetaminophen, and placebo on unresolved aches and discomfort as assessed by the brief pain inventory (BPI) and modified Cornell musculoskeletal discomfort questionnaires. This randomized, double-blind, placebo-controlled, crossover study consisted of three 7-day periods with Pain Bloc-R, acetaminophen, or placebo, each separated by a 7-day washout. Twenty-seven healthy adults (ages 22–63 years) were randomized to receive the three interventions in different sequences. The BPI “pain at its worst” scores were significantly lower when participants took Pain Bloc-R than when they took acetaminophen (21.8% vs. 9.8% decrease, p = 0.026) after seven days of supplementation. Pain Bloc-R achieved a significant improvement in the “pain at its least” score, significantly decreased the interference of discomfort in walking, and significantly decreased musculoskeletal discomfort total scores (34%, p = 0.040) after seven days. In a post hoc subgroup analysis based on age and gender, male participants ≤45 years taking Pain Bloc-R reported significant reductions in pain severity and pain interference vs. acetaminophen. Pain Bloc-R performed as well as acetaminophen in managing unresolved non-pathological pain in otherwise healthy individuals.

Reliability of the conditioned pain modulation paradigm across three anatomical sites

Background and aims Conditioned Pain Modulation (CPM) is a measure of pain inhibition-facilitation in humans that may elucidate pain mechanisms and potentially serve as a diagnostic test. In laboratory settings, the difference between two pain measures [painful test stimulus (TS) without and with the conditioning stimulus (CS) application] reflects the CPM magnitude. Before the CPM test can be used as a diagnostic tool, its reliability on the same day (intra-session) and across multiple days (inter-session) needs to be known. Furthermore, it is important to determine the most reliable anatomical sites for both the TS and the CS. This study aimed to measure the intra-session and inter-session reliability of the CPM test paradigm in healthy subjects with the TS (pressure pain threshold-PPT) applied to three test sites: the face, hand, and dorsum of the foot, and the CS (cold pressor test-CPT) applied to the contralateral hand. Methods Sixty healthy participants aged 18-65 were tested by the same examiner on 3 separate days, with an interval of 2-7 days. On each day, testing was comprised of two identical experimental sessions in which the PPT test was performed on each of the three dominant anatomical sites in randomized order followed by the CPM test (repeating the PPT with CPT on the non-dominant hand). CPM magnitude was calculated as the percent change in PPT. The Intraclass Correlation Coefficient (ICC), Coefficient of Variation (CV), and Bland-Altman analyses were used to assess reliability. Results PPT relative reliability ranged from good to excellent at all three sites; the hand showed an intra-session ICC of 0.90 (0.84, 0.94) before CPT and ICC of 0.89 (0.83, 0.92) during CPT. The PPT absolute reliability was also high, showing a low bias and small variability when performed on all three sites; for example, CV of the hand intra-session was 8.0 before CPT and 8.1 during CPT. The relative reliability of the CPM test, although only fair, was most reliable when performed during the intra-session visits on the hand; ICC of 0.57 (0.37, 0.71) vs. 0.20 (0.03, 0.39) for the face, and 0.22 (0.01, 0.46) for the foot. The inter-session reliability was lower in all three anatomical sites, with the best reliability on the hand with an ICC of 0.40 (0.23, 0.55). The pattern of absolute reliability of CPM was similar to the relative reliability findings, with the reliability best on the hand, showing lower intra-session and inter-session variability (CV% = 43.5 and 51.5, vs. 70.1 and 73.1 for the face, and 75.9 and 78.9 for the foot). The CPM test was more reliable in women than in men, and in older vs. younger participants. Discussion The CPM test was most reliable when the TS was applied to the dominant hand and CS performed on the contralateral hand. These data indicate that using the CS and TS in the same but contralateral dermatome in CPM testing may create the most reliable results.

Factors associated with diabetic polyneuropathy-related sensory symptoms and signs in patients with polyneuropathy: A cross-sectional Japanese study (JDDM 52) using a non-linear model

AIMS/INTRODUCTION

To assess the prevalence of diabetic polyneuropathy (DPN)-related sensory symptoms/signs and associated factors in patients with polyneuropathy, considering non-linear effects for numerical variables.

MATERIALS AND METHODS

A cross-sectional survey of patients with type 2 diabetes mellitus from 17 primary care clinics across Japan was carried out. DPN and DPN-related sensory symptoms/signs were diagnosed according to the Diabetic Neuropathy Study Group in Japan criteria.

RESULTS

Of the 9,914 patients with type 2 diabetes mellitus in this study, 2,745 had DPN and 1,689 had DPN-related sensory symptoms/signs (61.5% of patients with DPN). There were significant correlations between DPN-related sensory symptoms/signs and smoking status (odds ratio 2.04 for current and 1.64 for former; P < 0.001 and P = 0.002, respectively), sex (odds ratio 0.56 for male/female; P < 0.001) and alcohol consumption (odds ratio 2.02 for former/never; P = 0.004). Based on the non-linear logistic regression model, significant correlations were observed between the presence of DPN-related sensory symptoms/signs and higher systolic blood pressure (SBP), longer diabetes duration, and decreasing age. The logarithm of odds for SBP increased until reaching approximately 130 mmHg, then it plateaued.

CONCLUSIONS

Some modifiable factors assessed in the large survey database might be associated with DPN-related sensory symptoms/signs, namely smoking, alcohol consumption and SBP. Maintaining SBP <130 mmHg was associated with lower odds of DPN-related sensory symptoms/signs in patients with DPN.

Single nucleotide polymorphisms associated with postoperative inadequate analgesia after single-port VATS in Chinese population

Background

Postoperative inadequate analgesia following video-assisted thoracoscopic surgery (VATS) is a common and significant clinical problem. While genetic polymorphisms may play role in the variability of postoperative analgesia effect, few studies have evaluated the associations between genetic mutations and inadequate analgesia after single-port VATS.

Methods

Twenty-eight single nucleotide polymorphisms (SNPs) among 18 selected genes involved in pain perception and modulation were genotyped in 198 Chinese patients undergoing single-port VATS. The primary outcome was the occurrence of inadequate analgesia in the first night and morning after surgery which was defined by a comprehensive postoperative evaluation. Multivariable logistic regression analyses were used to identify the association between genetic variations and postoperative inadequate analgesia.

Results

The prevalence of postoperative inadequate analgesia was 45.5% in the present study. After controlling for age and education level, association with inadequate analgesia was observed in four SNPs among three genes encoding voltage-gated sodium channels. Patients with the minor allele of rs33985936 (SCN11A), rs6795970 (SCN10A), and 3312G > T (SCN9A) have an increased risk of suffering from inadequate analgesia. While the patients carrying the minor allele of rs11709492 (SCN11A) have lower risk experiencing inadequate analgesia.

Conclusions

We identified that SNPs in SCN9A, SCN10A, and SCN11A play a role in the postoperative inadequate analgesia after single-port VATS. Although future larger and long-term follow up studies are warranted to confirm our findings, the results of the current study may be utilized as predictors for forecasting postoperative analgesic effect for patients receiving this type of surgery.

Trial registration

This study was retrospectively registered in the ClinicalTrials.gov Registry (NCT03916120) on April 16, 2019.

Assessing peripheral fibers, pain sensitivity, central sensitization, and descending inhibition in Native Americans: main findings from the Oklahoma Study of Native American Pain Risk

Native Americans (NAs) have a higher prevalence of chronic pain than other U.S. racial/ethnic groups, but there have been few attempts to understand the mechanisms of this pain disparity. This study used a comprehensive battery of laboratory tasks to assess peripheral fiber function (cool/warm detection thresholds), pain sensitivity (eg, thresholds/tolerances), central sensitization (eg, temporal summation), and pain inhibition (conditioned pain modulation) in healthy, pain-free adults (N = 155 NAs, N = 150 non-Hispanic Whites [NHWs]). Multiple pain stimulus modalities were used (eg, cold, heat, pressure, ischemic, and electric), and subjective (eg, pain ratings and pain tolerance) and physiological (eg, nociceptive flexion reflex) outcomes were measured. There were no group differences on any measure, except that NAs had lower cold-pressor pain thresholds and tolerances, indicating greater pain sensitivity than NHWs. These findings suggest that there are no group differences between healthy NAs and NHWs on peripheral fiber function, central sensitization, or central pain inhibition, but NAs may have greater sensitivity to cold pain. Future studies are needed to examine potential within-group factors that might contribute to NA pain risk.

Pain-related anxiety promotes pronociceptive processes in Native Americans: bootstrapped mediation analyses from the Oklahoma Study of Native American Pain Risk

INTRODUCTION

Evidence suggests Native Americans (NAs) experience higher rates of chronic pain than the general US population, but the mechanisms contributing to this disparity are poorly understood. Recently, we conducted a study of healthy, pain-free NAs (n = 155), and non-Hispanic whites (NHWs, n = 150) to address this issue and found little evidence that NAs and NHWs differ in pain processing (assessed from multiple quantitative sensory tests). However, NAs reported higher levels of pain-related anxiety during many of the tasks.

OBJECTIVE

The current study is a secondary analysis of those data to examine whether pain-related anxiety could promote pronociceptive processes in NAs to put them at chronic pain risk.

METHODS

Bootstrapped indirect effect tests were conducted to examine whether pain-related anxiety mediated the relationships between race (NHW vs NA) and measures of pain tolerance (electric, heat, ischemia, and cold pressor), temporal summation of pain and the nociceptive flexion reflex (NFR), and conditioned pain modulation of pain/NFR.

RESULTS

Pain-related anxiety mediated the relationships between NA race and pain tolerance and conditioned pain modulation of NFR. Exploratory analyses failed to show that race moderated relationships between pain-related anxiety and pain outcomes.

CONCLUSION

These findings imply that pain-related anxiety is not a unique mechanism of pain risk for NAs, but that the greater tendency to experience pain-related anxiety by NAs impairs their ability to engage descending inhibition of spinal nociception and decreases their pain tolerance (more so than NHWs). Thus, pain-related anxiety may promote pronociceptive processes in NAs to place them at risk for future chronic pain.

Age does not affect sex effect of conditioned pain modulation of pressure and thermal pain across 2 conditioning stimuli

Introduction:

Conditioned pain modulation (CPM) is a laboratory test resulting in pain inhibition through activation of descending inhibitory mechanisms. Older adults consistently demonstrate reduced CPM compared with younger samples; however, studies of sex differences in younger cohorts have shown mixed results.

Objectives:

This study tested for sex differences in CPM within samples of younger and older adults.

Methods:

Participants were 67 younger adults (mean age = 25.4 years) and 50 older adults (66.4 years). Study conditioning paradigms were the cold-pressor test and contact heat pain administered in separate sessions. Pressure pain threshold and ramping suprathreshold heat were the test stimuli across three time points after presentation of the conditioning stimuli (CS).

Results:

Significant inhibition was observed during both testing sessions. The hypothesis for sex differences across both age cohorts was supported only for ∆PPTh. However, sex differences did not reach significance for either paradigm using ascending suprathreshold heat as the test stimuli. The overall trend was that younger males experienced the strongest CPM and older females the weakest. From a methodological perspective, duration differences were seen in CPM, with inhibition decaying more quickly for PPTh than for suprathreshold heat pain. Furthermore, there were no differences in inhibition induced by cold-pressor test and contact heat pain as CS.

Conclusion:

Sex differences were similar across both age cohorts with males experiencing greater inhibition than females. Cross-sectional associations were also demonstrated between CPM inhibition and measures of recent pain, further supporting CPM as an experimental model with clinical utility.

A Biopsychosocial Model of Chronic Pain for Older Adults

Population

Comprehensive evaluation of chronic pain in older adults is multifaceted.

Objective and Methods

Research on chronic pain in older adults needs to be guided by sound conceptual models. The purpose of this paper is to describe an adaptation of the Biopsychosocial Model (BPS) of Chronic Pain for older adults. The extant literature was reviewed, and selected research findings that provide the empiric foundation for this adaptation of the BPS model of chronic pain are summarized. The paper concludes with a discussion of specific recommendations for how this adapted model can be used to guide future research.

Conclusions

This adaptation of the BPS model of chronic pain for older adults provides a comprehensive framework to guide future research in this vulnerable population.

The impact of aging on pressure pain thresholds: are men less sensitive than women also in older age?

PURPOSE

Men have generally demonstrated higher pressure pain thresholds (PPT) than women. However, the possible impact of aging on the gender differences in pain perception has not been fully evaluated. In this study, we aimed to investigate the gender differences in PPT over the life course, in young, middle-aged and older adults.

METHODS

This cross-sectional study involved 355 pain-free healthy individuals aged 19-95 years, divided into < 45, 45-64 and ≥ 65 years age groups. PPT were measured using Fisher's algometer. Data on anthropometry, formal education and occupation were collected for each participant, and a multidimensional geriatric assessment was performed in older individuals.

RESULTS

Lower PPT values were observed in old vs young adults (21.8 ± 8.7 N/cm² vs 59.5 ± 31.6, p < 0.0001) and in women vs men (16.3 ± 6.1 vs 42.8 ± 19.6 N/cm², p = 0.0003). A significant interaction emerged between age and sex in influencing PPT (p_interaction = 0.03). Although women had lower mean PPT values than men in all age groups, such gender difference diminished with aging, from 42.8 ± 19.6 vs 59.5 ± 31.6 N/cm² (p = 0.001) to 16.3 ± 6.1 vs 21.8 ± 8.7 vs N/cm² (p = 0.003) in younger and older women vs men, respectively.

CONCLUSIONS

Female gender and older age are associated with lower PPT, but such gender difference seems to decrease with aging.

The Decline of Endogenous Pain Modulation With Aging: A Meta-Analysis of Temporal Summation and Conditioned Pain Modulation

The purpose of this article was to examine age-related changes in conditioned pain modulation (CPM) and temporal summation (TS) of pain using meta-analytic techniques. Five electronic databases were searched for studies, which compared measures of CPM and TS among healthy, chronic pain-free younger, middle-aged, and older adults. Eleven studies were included in the final review for TS and 11 studies were included in the review of CPM. The results suggested a moderate magnitude of difference in TS among younger and middle-aged/older adults, with the older cohorts exhibiting enhanced TS of pain. Considerable variability existed in the magnitude of the effect sizes, which was likely due to the different experimental methodologies used across studies (ie, interstimulus interval, stimulus type, and body location). In regards to CPM, the data revealed a large magnitude of difference between younger and older adults, with younger adults exhibiting more efficient pain inhibition. Differences in CPM between middle-aged and older adults were minimal. The magnitude of pain inhibition during CPM in older adults may depend on the use of concurrent versus nonconcurrent protocols. In summary, the data provided strong quantitative evidence of a general age-related decline in endogenous pain modulatory function as measured by TS and CPM. PERSPECTIVE: This review compared CPM and TS of pain among younger, middle-aged, and older adults. These findings enhance our understanding of the decline in endogenous pain modulatory function associated with normal aging.

Thermal and mechanical quantitative sensory testing values among healthy African American adults

PURPOSE

Only a few studies have reported quantitative sensory testing (QST) reference values for healthy African Americans, and those studies are limited in sample size and age of participants. The study purpose was to characterize QST values in healthy, pain-free African American adults and older adults whose prior pain experiences and psychological status were also measured. We examined the QST values for differences by sex, age, and body test site.

PATIENTS AND METHODS

A cross-sectional sample of 124 pain-free African American adults (age 18-69 years, 49% female) completed demographic and self-reported pain, fatigue and psychosocial measures. QST was performed to obtain thermal and mechanical responses and associated pain intensity levels.

RESULTS

We found thermal detection values at the anterior forearm were (29.2 °C±1.6) for cool detection (CD) and (34.5 °C±1.2) for warm detection (WD). At that site the sample had cold pain threshold (CPTh) (26.3 °C±5.0), heat pain threshold (HPTh) (37.8 °C±3.6), and mechanical pain thresholds (MPTH) (16.7±22.2 grams of force, gF). There was a significant between sex difference for WD, with women being more sensitive (q=0.027). Lower body sites were less sensitive than upper body sites across all thermal modalities (q<0.003), but not for the mechanical modality.

CONCLUSION

The QST values from this protocol at the anterior forearm indicate that the healthy African American adults had average thermal pain thresholds close to the temperature of adaptation and average MPTh under 20 gF. Differences in responses to thermal and mechanical stimuli for upper verses lower body were consistent with prior research.