Pain, aging, and the brain: new pieces to a complex puzzle

Age-related differences in functional connectivity associated with pain modulation

Growing evidence suggests that aging is associated with impaired endogenous pain modulation, and that this likely underlies the increased transition from acute to chronic pain in older individuals. Resting-state functional connectivity (rsFC) offers a valuable tool to examine the neural mechanisms behind these age-related changes in pain modulation. RsFC studies generally observe decreased within-network connectivity due to aging, but its relevance for pain modulation remains unknown. We compared rsFC within a set of brain regions involved in pain modulation between young and older adults and explored the relationship with the efficacy of distraction from pain. This revealed several age-related increases and decreases in connectivity strength. Importantly, we found a significant association between lower pain relief and decreased strength of three connections in older adults, namely between the periaqueductal gray and right insula, between the anterior cingulate cortex (ACC) and right insula, and between the ACC and left amygdala. These findings suggest that the functional integrity of the pain control system is critical for effective pain modulation, and that its function is compromised by aging.

The influence of advanced age on long-term postsurgical analgesic use in patients receiving neuraxial anaesthesia for elective surgery

OBJECTIVE

To determine the relationship between age and long-term postsurgical analgesic use in patients who underwent elective surgery with neuraxial anaesthesia.

DESIGN

Retrospective observational study using data from the National Health Insurance Research Database of Taiwan from 2015 to 2019.

SETTING

National Health Insurance Research Database of Taiwan.

PATIENTS

A total of 12,810 patients (6405 younger and 6405 older) matched using propensity score matching.

INTERVENTIONS

Older (≥65 years).

MEASUREMENTS

The use of long-term (3 or 6 months) postoperative analgesics, including opioids, as a surrogate marker of chronic postsurgical pain (CPSP) was analysed using logistic regression.

MAIN RESULTS

After 3 months of surgery, older adults had higher use of all analgesics (odds ratio [OR] = 1.15; 95% CI = 1.03-1.28) and opioids (OR = 1.18; 95% CI = 1.09-1.28) compared to younger patients. Similar results were observed after 6 months of surgery (all analgesic use: OR = 1.11; 95% CI = 1.03-1.20; opioid use: OR = 1.33; 95% CI = 1.07-1.81).

CONCLUSION

The findings from this study suggest that older adults are more likely to experience CPSP and have increased use of long-term analgesics, including opioids, after undergoing elective surgery with neuraxial anaesthesia. The study highlights the need for improved pain management strategies for older adults after surgery.

SIGNIFICANCE

Older age is an independent risk factor for long-term analgesic use after surgery under neuraxial anaesthesiaanesthesia, indicating an increased risk for chronic postsurgical pain.

Trajectories and contributing factors of neural compensation in healthy and pathological aging

Neural degeneration is a hallmark of healthy aging and can be associated with specific cognitive impairments. However, neural degeneration per se is not matched by unremitting declines in cognitive abilities. Instead, middle-aged and older adults typically maintain surprisingly high levels of cognitive functioning, suggesting that the human brain can adapt to structural degeneration by neural compensation. Here, we summarize prevailing theories and recent empirical studies on neural compensation with a focus on often neglected contributing factors, such as lifestyle, metabolism and neural plasticity. We suggest that these factors moderate the relationship between structural integrity and neural compensation, maintaining psychological well-being and behavioral functioning. Finally, we discuss that a breakdown in neural compensation may pose a tipping point that distinguishes the trajectories of healthy vs pathological aging, but conjoint support from psychology and cognitive neuroscience for this alluring view is still scarce. Therefore, future experiments that target the concomitant processes of neural compensation and associated behavior will foster a comprehensive understanding of both healthy and pathological aging.

Brain-predicted age difference mediates the association between PROMIS sleep impairment, and self-reported pain measure in persons with knee pain

Knee pain, the most common cause of musculoskeletal pain (MSK), constitutes a severe public health burden. Its neurobiological causes, however, remain poorly understood. Among many possible causes, it has been proposed that sleep problems could lead to an increase in chronic pain symptomatology, which may be driven by central nervous system changes. In fact, we previously found that brain cortical thickness mediated the relationship between sleep qualities and pain severity in older adults with MSK. We also demonstrated a significant difference in a machine-learning-derived brain-aging biomarker between participants with low-and high-impact knee pain. Considering this, we examined whether brain aging was associated with self-reported sleep and pain measures, and whether brain aging mediated the relationship between sleep problems and knee pain. Exploratory Spearman and Pearson partial correlations, controlling for age, sex, race and study site, showed a significant association of brain aging with sleep related impairment and self-reported pain measures. Moreover, mediation analysis showed that brain aging significantly mediated the effect of sleep related impairment on clinical pain and physical symptoms. Our findings extend our prior work demonstrating advanced brain aging among individuals with chronic pain and the mediating role of brain-aging on the association between sleep and pain severity. Future longitudinal studies are needed to further understand whether the brain can be a therapeutic target to reverse the possible effect of sleep problems on chronic pain.

Brain predicted age difference mediates pain impact on physical performance in community dwelling middle to older aged adults

The purpose of the study was to examine associations between physical performance and brain aging in individuals with knee pain and whether the association between pain and physical performance is mediated by brain aging. Participants (n=202) with low impact knee pain (n=111), high impact knee pain (n=60) and pain-free controls (n=31) completed self-reported pain, magnetic resonance imaging (MRI), and a Short Physical Performance Battery (SPPB) that included balance, walking, and sit to stand tasks. Brain predicted age difference, calculated using machine learning from MRI images, significantly mediated the relationships between walking and knee pain impact (CI: -0.124; -0.013), walking and pain-severity (CI: -0.008; -0.001), total SPPB score and knee pain impact (CI: -0.232; -0.025), and total SPPB scores and pain-severity (CI: -0.019; -0.001). Brain-aging begins to explain the association between pain and physical performance, especially walking. This study supports the idea that a brain aging prediction can be calculated from shorter duration MRI sequences and possibly implemented in a clinical setting to be used to identify individuals with pain who are at risk for accelerated brain atrophy and increased likelihood of disability.

Epigenetic Aging Mediates the Association between Pain Impact and Brain Aging in Middle to Older Age Individuals with Knee Pain

Chronic musculoskeletal pain is a health burden that may accelerate the aging process. Accelerated brain aging and epigenetic aging have separately been observed in those with chronic pain. However, it is unknown whether these biological markers of aging are associated with each other in those with chronic pain. We aimed to explore the association of epigenetic aging and brain aging in middle-to-older age individuals with varying degrees of knee pain. Participants (57.91 ± 8.04 y) with low impact knee pain (n = 95), high impact knee pain (n = 53), and pain-free controls (n = 26) completed self-reported pain, a blood draw, and an MRI scan. We used an epigenetic clock previously associated with knee pain (DNAmGrimAge), the subsequent difference of predicted epigenetic and brain age from chronological age (DNAmGrimAge-Difference and Brain-PAD, respectively). There was a significant main effect for pain impact group (F (2,167) = 3.847, P = 0.023, r o t a t i o n a l   e n e r g y   =   1 / 2 I ω 2 = 0.038, ANCOVA) on Brain-PAD and DNAmGrimAge-difference (F (2,167) = 6.800, P = 0.001, I   =   m k 2 = 0.075, ANCOVA) after controlling for covariates. DNAmGrimAge-Difference and Brain-PAD were modestly correlated (r =0.198; P =0.010). Exploratory analysis revealed that DNAmGrimAge-difference mediated GCPS pain impact, GCPS pain severity, and pain-related disability scores on Brain-PAD. Based upon the current study findings, we suggest that pain could be a driver for accelerated brain aging via epigenome interactions.

Cross-Sectional Brain-Predicted Age Differences in Community-Dwelling Middle-Aged and Older Adults with High Impact Knee Pain

Purpose

Knee OA-related pain varies in impact across individuals and may relate to central nervous system alterations like accelerated brain aging processes. We previously reported that older adults with chronic musculoskeletal pain had a significantly greater brain-predicted age, compared to pain-free controls, indicating an "older" appearing brain. Yet this association is not well understood. This cross-sectional study examines brain-predicted age differences associated with chronic knee osteoarthritis pain, in a larger, more demographically diverse sample with consideration for pain's impact.

Patients and Methods

Participants (mean age = 57.8 ± 8.0 years) with/without knee OA-related pain were classified according to pain's impact on daily function (ie, impact): low-impact (n=111), and high-impact (n=60) pain, and pain-free controls (n=31). Participants completed demographic, pain, and psychosocial assessments, and T1-weighted magnetic resonance imaging. Brain-predicted age difference (brain-PAD) was compared across groups using analysis of covariance. Partial correlations examined associations of brain-PAD with pain and psychosocial variables.

Results

Individuals with high-impact chronic knee pain had significantly "older" brains for their age compared to individuals with low-impact knee pain (p < 0.05). Brain-PAD was also significantly associated with clinical pain, negative affect, passive coping, and pain catastrophizing (p's<0.05).

Conclusion

Our findings suggest that high impact chronic knee pain is associated with an older appearing brain on MRI. Future studies are needed to determine the impact of pain-related interference and pain management on somatosensory processing and brain aging biomarkers for high-risk populations and effective intervention strategies.

Clinical vitamin D levels are associated with insular volume and inferior temporal gyrus white matter surface area in community-dwelling individuals with knee pain

Context

Vitamin D is an essential, fat soluble micronutrient long-known for its effects on calcium homeostasis and bone health. With advances in technology, it is being discovered that Vitamin D exerts its effects beyond the musculoskeletal system. Vitamin D has since been noted in nervous system health and functioning, and is becoming a target of interest in brain health, aging, and chronic pain outcomes.

Objectives

We and others have previously shown that deficient Vitamin D status is associated with greater pain severity across a variety of conditions, however the reason as to why this relationship exists is still being understood. Here, we sought to examine associations between Vitamin D status and brain structure in those with chronic knee pain.

Methods

Structural MRI imaging techniques and whole brain analyses were employed and serum Vitamin D were collected on 140 participants with chronic pain. Covariates included age, sex, race and site, as these data were collected at two separate institutions. ANOVAs using the clinical cut points for Vitamin D status (deficient, insufficient, and optimal) as well as continuous regression-based Vitamin D effects were employed to observe differences in brain volume. P-value was set to 0.017 after correction for multiple comparisons.

Results

We discovered that individuals in our sample (age = 50+; 63.6% female; 52.1% Non-Hispanic Black) who were either clinically deficient (<20 ng/mL) or insufficient (20-30 ng/mL) in serum Vitamin D had significant differences in the gray matter of the left circular insular cortex, left inferior temporal gyrus, right middle temporal gyrus, as well as decreased white matter surface area in the right inferior temporal gyrus compared to those considered to have optimal levels (>30 ng/mL) of serum Vitamin D.

Conclusion

Evidence from these data suggests that Vitamin D, or lack thereof, may be associated with pain outcomes by mediating changes in regions of the brain known to process and interpret pain. More research understanding this phenomenon as well as the effects of Vitamin D supplementation is warranted.

Epigenetic age predictors in community-dwelling adults with high impact knee pain

Gerontological research reveals considerable interindividual variability in aging phenotypes, and emerging evidence suggests that high impact chronic pain may be associated with various accelerated biological aging processes. In particular, epigenetic aging is a robust predictor of health-span and disability compared to chronological age alone. The current study aimed to determine whether several epigenetic aging biomarkers were associated with high impact chronic pain in middle to older age adults (44–78 years old). Participants (n = 213) underwent a blood draw, demographic, psychosocial, pain and functional assessments. We estimated five epigenetic clocks and calculated the difference between epigenetic age and chronological age, which has been previously reported to predict overall mortality risk, as well as included additional derived variables of epigenetic age previously associated with pain. There were significant differences across Pain Impact groups in three out of the five epigenetic clocks examined (DNAmAge, DNAmPhenoAge and DNAmGrimAge), indicating that pain-related disability during the past 6 months was associated with markers of epigenetic aging. Only DNAmPhenoAge and DNAmGrimAge were associated with higher knee pain intensity during the past 48 h. Finally, pain catastrophizing, depressive symptomatology and more neuropathic pain symptoms were significantly associated with an older epigenome in only one of the five epigenetic clocks (i.e. DNAmGrimAge) after correcting for multiple comparisons (corrected p’s < 0.05). Given the scant literature in relation to epigenetic aging and the complex experience of pain, additional research is needed to understand whether epigenetic aging may help identify people with chronic pain at greater risk of functional decline and poorer health outcomes.

Interface of Aging and Acute Peripheral Neuropathy Induced by Oxaliplatin in Mice: Target-Directed Approaches for Na+, K+-ATPase, Oxidative Stress, and 7-Chloro-4-(phenylselanyl) quinoline Therapy

Almost 90% of patients develop pain immediately after oxaliplatin (OXA) treatment. Here, the impact of aging on OXA-induced acute peripheral neuropathy and the potential of 7-chloro-4-(phenylselanyl) quinoline (4-PSQ) as a new therapeutic strategy were evaluated. In Swiss mice, the oxidative damage and its influence on Mg²⁺-ATPase and Na⁺, K⁺-ATPase activities were investigated. The relationship between the reactive oxygen species (ROS) and nitrate and nitrite (NOx) levels, the activity of glutathione peroxidase (GPx), and superoxide dismutase (SOD) with the development of OXA-induced acute peripheral neuropathy was also studied. In this study, it was evidenced that OXA-induced acute peripheral neuropathy was exacerbated by aging through increased oxidative damage as well as Na⁺, K⁺-ATPase, and Mg⁺²-ATPase inhibition. 4-PSQ reversed hypersensitivity induced by OXA and aging-aggravated by reducing ROS and NOx levels, through modulation of GPx and SOD activities. 4-PSQ partially reestablish Na⁺, K⁺-ATPase activity, but not Mg ²⁺-ATPase activity. Locomotor and exploratory activities were not affected. This study is the first of its kind, providing new insight into the aging impact on mechanisms involved in OXA-induced acute peripheral neuropathy. Also, it provides evidence on promising 4-PSQ effects on this condition, mainly on aging.

Brain gamma-aminobutyric acid, but not glutamine and glutamate levels are lower in older adults with chronic musculoskeletal pain: considerations by sex and brain location

INTRODUCTION AND OBJECTIVES

GABAergic and glutamatergic neurotransmitter systems are central to the pathophysiology of chronic pain and are equally affected by aging processes. We measured levels of frontal gamma-aminobutyric acid (GABA) and the combined resonance of glutamate and glutamine (Glx) in vivo using proton magnetic resonance spectroscopy (1H-MRS) to elucidate age-specific and pain-specific associations with clinical and experimental pain in older adults.

METHODS

Younger (18-24, n = 24) and older (60-94, n = 41) individuals part of a larger study (Neuromodulatory Examination of Pain and Mobility Across the Lifespan [NEPAL]) underwent questionnaires, quantitative sensory testing, and 1H-MRS Mescher-Garwood point-resolved spectroscopy to measure GABA and Glx levels in prefrontal and sensorimotor brain regions.

RESULTS

Older participants had significantly lower sensorimotor, but not prefrontal, GABA and Glx levels, compared with younger controls (P's < 0.05). Younger controls had significantly higher prefrontal and sensorimotor GABA, but not Glx, levels compared with older controls and older adults with chronic pain (P's < 0.05). Older males with chronic pain had significantly lower prefrontal GABA compared with older and younger male controls (P's < 0.05). Prefrontal GABA, but not Glx, was significantly associated with self-reported and experimental pain measures (P's < 0.05). Our results are the first to focus exclusively on age and pain differences in GABA and Glx including younger and older controls to elucidate aging and pain contributions to brain GABAergic and glutamatergic processes.

CONCLUSION

Evaluation of both the neuroinhibitory and neuroexcitatory mechanisms provide promising potential for improving both our understanding of the mechanisms of chronic pain in aging and opportunities for effective, individualized treatments.

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.

Analysis of Epigenetic Age Predictors in Pain-Related Conditions

Chronic pain prevalence is high worldwide and increases at older ages. Signs of premature aging have been associated with chronic pain, but few studies have investigated aging biomarkers in pain-related conditions. A set of DNA methylation (DNAm)-based estimates of age, called “epigenetic clocks,” has been proposed as biological measures of age-related adverse processes, morbidity, and mortality. The aim of this study is to assess if different pain-related phenotypes show alterations in DNAm age. In our analysis, we considered three cohorts for which whole-blood DNAm data were available: heat pain sensitivity (HPS), including 20 monozygotic twin pairs discordant for heat pain temperature threshold; fibromyalgia (FM), including 24 cases and 20 controls; and headache, including 22 chronic migraine and medication overuse headache patients (MOH), 18 episodic migraineurs (EM), and 13 healthy subjects. We used the Horvath's epigenetic age calculator to obtain DNAm-based estimates of epigenetic age, telomere length, levels of 7 proteins in plasma, number of smoked packs of cigarettes per year, and blood cell counts. We did not find differences in epigenetic age acceleration, calculated using five different epigenetic clocks, between subjects discordant for pain-related phenotypes. Twins with high HPS had increased CD8+ T cell counts (nominal p = 0.028). HPS thresholds were negatively associated with estimated levels of GDF15 (nominal p = 0.008). FM patients showed decreased naive CD4+ T cell counts compared with controls (nominal p = 0.015). The severity of FM manifestations expressed through various evaluation tests was associated with decreased levels of leptin, shorter length of telomeres, and reduced CD8+ T and natural killer cell counts (nominal p < 0.05), while the duration of painful symptoms was positively associated with telomere length (nominal p = 0.034). No differences in DNAm-based estimates were detected for MOH or EM compared with controls. In summary, our study suggests that HPS, FM, and MOH/EM do not show signs of epigenetic age acceleration in whole blood, while HPS and FM are associated with DNAm-based estimates of immunological parameters, plasma proteins, and telomere length. Future studies should extend these observations in larger cohorts.