Sleep restriction attenuates amplitudes and attentional modulation of pain-related evoked potentials, but augments pain ratings in healthy volunteers

Impact of one night of sleep restriction on sleepiness and cognitive function: A systematic review and meta-analysis

Detrimental consequences of chronic sleep restriction on cognitive function are well established in the literature. However, effects of a single night of sleep restriction remain equivocal. Therefore, we synthesized data from 44 studies to investigate effects of sleep restriction to 2-6 h sleep opportunity on sleepiness and cognition in this meta-analysis. We investigated subjective sleepiness, sustained attention, choice reaction time, cognitive throughput, working memory, and inhibitory control. Results revealed a significant increase in subjective sleepiness following one night of sleep restriction (Standardized Mean Difference (SMD) = 0.986, p < 0.001), while subjective sleepiness was not associated with sleep duration during sleep restriction (β = -0.214, p = 0.039, significance level 0.01). Sustained attention, assessed via common 10-min tasks, was impaired, as demonstrated through increased reaction times (SMD = 0.512, p < 0.001) and attentional lapses (SMD = 0.489, p < 0.001). However, the degree of impaired attention was not associated with sleep duration (ps > 0.090). We did not find significant effects on choice reaction time, cognitive throughput, working memory, or inhibitory control. Overall, results suggest that a single night of restricted sleep can increase subjective sleepiness and impair sustained attention, a cognitive function crucial for everyday tasks such as driving.

Does Melatonin Improve Sleep Following Primary Total Knee Arthroplasty? A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND

Sleep impairment following total knee arthroplasty (TKA) is common and may decrease patient satisfaction and recovery. Standardized postoperative recommendations for sleep disturbances have not been established. We aimed to assess whether melatonin use could promote healthy sleep and reduce sleep disturbance in the acute period following TKA.

METHODS

Patients undergoing primary, elective TKA between July 19, 2021 and January 4, 2024 were prospectively enrolled and randomized to receive either 5 mg of melatonin nightly or placebo for 14 days postoperatively. Participants recorded their nightly pain on the visual analog scale, the number of hours slept, and the number of night-time awakenings in a sleep diary starting the night of surgery (postoperative day [POD] 0). Sleep disturbance was assessed preoperatively and on POD 14 using the patient-reported outcome measurement information system sleep disturbance form. Epworth Sleepiness Scores were collected on POD 14 to assess sleep quality.

RESULTS

Of the 138 patients enrolled, 128 patients successfully completed the study protocol, with 64 patients in each group. Melatonin patients trended toward more hours of sleep on POD 2 (placebo: 5.0 ± 2.4, melatonin: 5.8 ± 2.0, P = .084), POD 3 (placebo: 5.6 ± 2.2, melatonin: 6.3 ± 2.0, P = .075), and averaged over POD 1 to 3 (placebo: 4.9 ± 2.0, melatonin: 5.6 ± 1.8, P = .073), although no differences were observed on POD 4 or after. Fewer night-time awakenings in the melatonin group were observed on POD 1 (placebo: 4.4 ± 3.9, melatonin: 3.6 ± 2.4, P = .197), although this was not statistically significant. Preoperative and postoperative Patient-Reported Outcomes Measurement Information System Sleep Disturbance score increases were comparable for both groups (placebo: 4.0 ± 8.4, melatonin: 4.6 ± 8.2, P = .894). The melatonin (65.4%) and placebo (65%) groups demonstrated similar rates of increased sleep disturbance.

CONCLUSIONS

Melatonin may promote longer sleep in the immediate postoperative period after TKA, although these benefits wane after POD 3. Disturbances in sleep should be expected for most patients, although melatonin may have an attenuating effect. Melatonin is safe and can be considered for TKA patients experiencing early sleep disturbances postoperatively.

Pain is what hurts: An exploration of perception and management of pain in peripheral blood stem cell donors

BACKGROUND

Pain is a side effect of Granulocyte-Colony Stimulating Factor (G-CSF) administration. This prospective study investigates various aspects including pain perception occurring in Peripheral Blood Stem Cell (PBSC) donors.

MATERIALS AND METHODS

Related and unrelated PBSC donors were prospectively studied. Donors recorded pain symptoms during the four-day period of G-CSF administration using the McGill Pain Questionnaire, a Visual Analog Scale and a pain diary.

RESULTS

There were 208 donors included, 102 (49%) related and 106 (51%) unrelated donors. Ninety-two percent of all reported the occurrence of pain. Moderate or severe pain was reported by 52%. No differences were found between related and unrelated donors. Pain occurred more often in females (p = 0.035). Relatively young donors (age 16-30 years) more frequently showed to have pain in comparison to older donors (>50 years) (p = 0.006). Musculoskeletal pain was most frequently distributed in the gluteal and lower back region (65-71%). Irrespective of the pain location, pain was most often described as nagging, annoying, however tolerable. Donors experiencing pain most on days of G-CSF administration, most frequently occurring during relaxation or at night. Sleep-mode was often affected. The use of paracetamol (acetaminophen) was sufficient for all but one donor.

CONCLUSION

This is the first study to describe different aspects of pain associated with G-CSF administration in donors. Although the observed pain was tolerable, it should never be neglected. Knowledge derived from this study is of use for staff members involved in donor information and care management.

Mapping the associations of daily pain, sleep, and psychological distress in a U.S. sample

Chronic pain, sleep problems, and psychological distress (PD) can be disabling conditions and previous research has shown that they are associated. The nuances of the comorbid nature of these conditions may be important to understand for those who treat these conditions. This study examined the bidirectional associations of these health factors concurrently and over time in a sample of U.S. adults (N = 1,008, Mage = 57.68) from the Midlife in the United States (MIDUS) study. Participants reported on their daily pain, sleep quantity, and psychological distress over eight days. A modified Random Intercept Cross-lagged Panel Model was used to analyze the relations, starting with the whole sample and then a comparison of those with and without chronic pain. Results indicated that nightly variation in sleep quantity predicted next day psychological distress for both groups. Sleep quantity also predicted next-day pain, but only for individuals with chronic pain. Associations between pain and psychological distress were found both at the daily level and individual (between-person) level. This between-person association was stronger for those with chronic pain. The lagged associations between sleep, and both pain and psychological distress for the chronic pain group indicate that, increased quantity of sleep predicts decreased next-day pain and psychological distress. Providers could consider this unidirectional lagged relationship when prioritizing treatment for patients with these comorbid conditions. Future research may examine whether responsive, just-in-time treatments might intervene after participants wake from a poor night's sleep to counteract the negative effects of reduced sleep on PD and pain.

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.

Catastrophizing and acceptance are mediators between insomnia and pain intensity-an SQRP study of more than 6,400 patients with non-malignant chronic pain conditions

Background

Sleep problems (insomnia) and chronic pain are associated. Chronic pain and insomnia/insufficient sleep quality share similar symptoms and features. Although they have a bidirectional relationship, more research is needed to understand how they interact via mediators and how moderators influence this relationship.

Aims

In this large clinical registry-based cohort study (N = 6,497), we investigate important mediators between insomnia and pain intensity in a cross-sectional sample of chronic pain patients using advanced path analysis. In addition, we investigate whether some background variables were moderators of the identified important paths or not and the correlation patterns between insomnia and pain intensity in relation to the mediators.

Methods

This study includes a cohort of adult patients with chronic non-cancer pain from the Swedish Quality Registry for Pain Rehabilitation (SQRP) with data on patient-reported outcome measures (PROMs) (2008-2016). The PROMs cover the background, pain aspects, psychological distress, pain-related cognitions, activity/participation, and health-related quality of life variables of the patients. Partial least squares structural equation modeling was used to explore the direct and indirect (via mediators) relationships between insomnia and pain intensity at baseline.

Results

In this cohort study, insomnia was prevalent at 62.3%, and both direct and indirect mediating paths were present for the insomnia-pain intensity relationship. All of the mediating effects combined were weaker than the direct effect between insomnia and pain intensity. The mediating effects via catastrophizing and acceptance showed the strongest and equal mediating paths, and mediating effects via fear avoidance were the second strongest. Insomnia showed stronger direct significant correlations with psychological distress, catastrophizing, and acceptance compared with those of pain intensity. Sex, age, education level, spatial extent of pain, or body mass index did not moderate the mediating paths.

Discussion and conclusion

This study confirms the existence of significant direct and mediating paths between reported insomnia and pain intensity. Future studies should focus on illuminating how sleep interventions influence pain intensity and other important key factors that contribute to the distress of chronic pain patients.

Sleep Deprivation and Its Consequences

OBJECTIVE

This article reviews the clinical, cognitive, behavioral, and physiologic consequences of sleep deprivation in relation to general neurology practice.

LATEST DEVELOPMENTS

Despite being one of the most common sleep problems in modern society, the role of sleep deprivation is underrecognized and underestimated in clinical medicine and general neurology practice. The recognition, diagnosis, and management of sleep deprivation in neurologic practice have only recently received close attention. The consequences of sleep deprivation involve all aspects of general neurology practice, including individuals with neurologic disease, neurologists, communities, and health care systems. The identification and timely management of sleep deprivation symptoms may help to improve symptoms of underlying primary neurologic disorders.

ESSENTIAL POINTS

This article emphasizes complexities related to the identification and evaluation of sleep deprivation in general neurology practice and describes the consequences of sleep deprivation. By recognizing sleep deprivation in patients with neurologic conditions, the neurologist can provide comprehensive care and contribute to improved clinical and neurologic outcomes.

Modeling homeostatic and circadian modulation of human pain sensitivity

Introduction

Mathematical modeling has played a significant role in understanding how homeostatic sleep pressure and the circadian rhythm interact to influence sleep-wake behavior. Pain sensitivity is also affected by these processes, and recent experimental results have measured the circadian and homeostatic components of the 24 h rhythm of thermal pain sensitivity in humans. To analyze how rhythms in pain sensitivity are affected by disruptions in sleep behavior and shifts in circadian rhythms, we introduce a dynamic mathematical model for circadian and homeostatic regulation of sleep-wake states and pain intensity.

Methods

The model consists of a biophysically based, sleep-wake regulation network model coupled to data-driven functions for the circadian and homeostatic modulation of pain sensitivity. This coupled sleep-wake-pain sensitivity model is validated by comparison to thermal pain intensities in adult humans measured across a 34 h sleep deprivation protocol.

Results

We use the model to predict dysregulation of pain sensitivity rhythms across different scenarios of sleep deprivation and circadian rhythm shifts, including entrainment to new environmental light and activity timing as occurs with jet lag and chronic sleep restriction. Model results show that increases in pain sensitivity occur under conditions of increased homeostatic sleep drive with nonlinear modulation by the circadian rhythm, leading to unexpected decreased pain sensitivity in some scenarios.

Discussion

This model provides a useful tool for pain management by predicting alterations in pain sensitivity due to varying or disrupted sleep schedules.

Sleep quality as a mediator of the relation between depression and chronic pain: a systematic review and meta-analysis

BACKGROUND

Chronic pain and depression represent two global health problems with considerable economic consequences. Although existing literature reports on the relation between depression and pain conditions, meta-analytic evidence backing the mediating role of sleep disturbance as one of the main symptoms of depression is scarce. To examine the extent to which sleep disturbance mediates the depression-chronic pain association, we conducted a systematic review and meta-analysis of the associations of chronic pain, depression, and sleep quality.

METHODS

We systematically searched for literature in MEDLINE and other relevant databases and identified cohort and case-control studies on depression, sleep disturbance, and chronic pain. Forty-nine studies were eligible, with a total population of 120 489 individuals. We obtained direct and indirect path coefficients via two-stage meta-analytic structural equation modelling, examined heterogeneity via subgroup analyses, and evaluated primary studies quality.

RESULTS

We found a significant, partial mediation effect of sleep disturbance on the relation between depression and chronic pain. The pooled path coefficient (coef.) of the indirect effect was 0.03 (95% confidence interval [CI]: 0.01-0.05) and accounted for 12.5% of the total effect of depression on chronic pain. This indirect effect also existed for cohort studies (coef. 0.02; 95% CI: 0.002-0.04), European studies (coef. 0.03; 95% CI: 0.004-0.05), and studies that adjusted for confounders (coef. 0.04; 95% CI: 0.01-0.09).

CONCLUSIONS

Sleep disturbance partially mediates the association between depression and pain. Although plausible mechanisms could explain this mediation effect, other explanations, including reverse causation, must be further explored.

SYSTEMATIC REVIEW PROTOCOL

PROSPERO CRD42022338201.

Investigation of pain sensitivity following 3 nights of disrupted sleep in healthy individuals

BACKGROUND

Poor quality sleep is a common complaint among people with chronic pain. The co-occurrence of poor sleep quality and chronic pain often comes with increased pain intensity, more disability and a higher cost of healthcare. Poor sleep has been suggested to affect measures of peripheral and central pain mechanisms. To date, sleep provocations are the only models proven to affect measures of central pain mechanisms in healthy subjects. However, there are limited studies investigating the effect of several nights of sleep disruption on measures of central pain mechanisms.

METHODS

The current study implemented three nights of sleep disruption with three planned awakenings per night in 30 healthy subjects sleeping at home. Pain testing was conducted at the same time of day at baseline and follow-up for each subject. Pressure pain thresholds were assessed bilaterally on the infraspinatus and gastrocnemius muscles. Using handheld pressure algometry, suprathreshold pressure pain sensitivity and area were also investigated on the dominant infraspinatus muscle. Cuff-pressure pain detection and tolerance thresholds, temporal summation of pain and conditioned pain modulation were investigated using cuff-pressure algometry.

RESULTS

Temporal summation of pain was significantly facilitated (p = 0.022), suprathreshold pain areas (p = 0.005) and intensities (p < 0.05) were significantly increased, and all pressure pain thresholds were decreased (p < 0.005) after sleep disruption compared to baseline.

CONCLUSIONS

The current study found that three consecutive nights of sleep disruption at home induced pressure hyperalgesia and increased measures of pain facilitation in healthy subjects, which is consistent with previous findings.

SIGNIFICANCE

Poor quality of sleep is often experienced by patients with chronic pain, with the most common complaint being nightly awakenings. This exploratory study is the first to investigate changes in measures of central and peripheral pain sensitivity in healthy subjects after sleep disruptions for three consecutive nights without any restrictions on total sleep time. The findings suggest that disruptions to sleep continuity in healthy individuals can induce increased sensitivity to measures of central and peripheral pain sensitization.

A nationwide study on pain manifestations and sleep problems in community-dwelling older adults: findings from ELSI-Brazil

PURPOSE

Sleep problems are common and affect approximately 36-70% of older adults worldwide and can be associated with negative outcomes such as pain. There is believed to be a bidirectional relationship between sleep problems and pain, modulated by inflammation and stress. The objective was to investigate the association between self-reported sleep problems and pain manifestations.

METHODS

A cross-sectional study using data from the second wave of the Brazilian Longitudinal Study of Aging (2019-2021) was conducted. The exposure variables were self-reported sleep problems: poor sleep quality, insomnia (initial, intermediate, and final), and daytime sleepiness. The outcomes were self-reported pain manifestations: frequent pain, moderate/intense/strong pain, and pain-related disability. Logistic regressions were performed to verify the association between exposures and outcomes.

RESULTS

A total of 6875 community-dwelling older adults participated in this study (71.1 ± 8.3 years; 54.4% female). Older adults with self-reported poor sleep quality, initial, intermediate and final insomnia, and daytime sleepiness had, respectively, 1.99 (95% CI 1.57-2.53), 1.47 (95% CI 1.11-1.97), 1.65 (95% CI 1.27-2.14), 1.69 (95% CI 1.29-2.22), and 1.76 (95% CI 1.35-2.29) greater odds of reporting frequent pain. The odds of moderate/intense/strong pain were higher in older adults that reported poor sleep quality (OR: 2.21; 95% CI 1.08-4.51). Older adults with self-reported poor sleep quality, initial, intermediate and final insomnia, and daytime sleepiness had, respectively, 1.84 (95% CI 1.11-3.02), 1.73 (95% CI 1.14-2.62), 1.80 (95% CI 1.19-2.73), 1.58 (95% CI 1.07-2.34), and 1.63 (95% CI 1.11-2.39) greater odds of reporting pain-related disability.

CONCLUSION

Self-reported sleep problems are associated with pain manifestations in older adults. The results may help in the proposition of programs and public health policies.

Effect of sleep loss on pain-New conceptual and mechanistic avenues

Introduction

Sleep disturbances increase pain sensitivity in clinical and preclinical settings, but the precise mechanisms are unknown. This represents a major public health issue because of the growing sleep deficiency epidemic fueled by modern lifestyle. To understand the neural pathways at the intersection between sleep and pain processes, it is critical to determine the precise nature of the sleep disruptions that increase pain and the specific component of the pain response that is targeted.

Methods

We performed a review of the literature about sleep disturbances and pain sensitivity in humans and rodents by taking into consideration the targeted sleep stage (REMS, non-NREMS, or both), the amount of sleep lost, and the different types of sleep disruptions (partial or total sleep loss, duration, sleep fragmentation or interruptions), and how these differences might affect distinct components of the pain response.

Results

We find that the effects of sleep disturbances on pain are highly conserved among species. The major driver for pain hypersensitivity appears to be the total amount of sleep lost, while REMS loss by itself does not seem to have a direct effect on pain sensitivity. Sleep loss caused by extended wakefulness preferentially increases pain perception, whereas interrupted and limited sleep strongly dysregulates descending controls such as DNIC, especially in women.

Discussion

We discuss the possible mechanisms involved, including an increase in inflammatory processes, a loss of nociceptive inhibitory pathways, and a defect in the cognitive processing of noxious input.

Preoperative Acute Sleep Deprivation Causes Postoperative Pain Hypersensitivity and Abnormal Cerebral Function

Preoperative sleep loss can amplify post-operative mechanical hyperalgesia. However, the underlying mechanisms are still largely unknown. In the current study, rats were randomly allocated to a control group and an acute sleep deprivation (ASD) group which experienced 6 h ASD before surgery. Then the variations in cerebral function and activity were investigated with multi-modal techniques, such as nuclear magnetic resonance, functional magnetic resonance imaging, c-Fos immunofluorescence, and electrophysiology. The results indicated that ASD induced hyperalgesia, and the metabolic kinetics were remarkably decreased in the striatum and midbrain. The functional connectivity (FC) between the nucleus accumbens (NAc, a subregion of the ventral striatum) and the ventrolateral periaqueductal gray (vLPAG) was significantly reduced, and the c-Fos expression in the NAc and the vLPAG was suppressed. Furthermore, the electrophysiological recordings demonstrated that both the neuronal activity in the NAc and the vLPAG, and the coherence of the NAc-vLPAG were suppressed in both resting and task states. This study showed that neuronal activity in the NAc and the vLPAG were weakened and the FC between the NAc and the vLPAG was also suppressed in rats with ASD-induced hyperalgesia. This study highlights the importance of preoperative sleep management for surgical patients.

Bidirectional associations between chronic low back pain and sleep quality: A cohort study with schoolteachers

AIMS

Although both chronic low back pain (cLBP) and sleep problems are prevalent among active workers, the relation between these variables is not well established. This study aimed to examine the bidirectional association between cLBP and sleep in schoolteachers.

METHODS

The Pittsburgh Sleep Quality Index (PSQI) and cLBP were self-reported by 530 schoolteachers in Londrina, Brazil, at baseline and after 2 years of follow-up. Generalized estimating equations were adjusted for sociodemographic, lifestyle and mental health variables.

RESULTS

Poor sleep quality at baseline was associated with cLBP at follow-up after adjusting for sociodemographic and lifestyle variables (OR=1.61; 95% confidence interval [95% CI]=1.06, 2.47). Changes in the PSQI score over time were also associated with a higher likelihood of cLBP at follow-up (OR=1.13; 95% CI=1.07, 1.20 for each 1-point increase in the PSQI score), regardless of mental health condition. cLBP at baseline was associated with worse sleep quality at follow-up after adjusting for sociodemographic and lifestyle variables (OR=1.56; 95% CI=1.02, 2.37). The presence of cLBP also changed the PSQI score over time (ß coefficient=1.153; 95% CI=0.493, 1.814).

CONCLUSIONS

Worse sleep quality was prospectively and bidirectionally associated with cLBP. Concretely, changes in PSQI values after 2 years of follow-up increased the likelihood of reporting cLBP, and baseline cLBP was associated with sleep quality worsening (i.e., higher score in the PSQI). Mental health conditions such as self-rated health, depression and anxiety play a relevant confounding role in the bidirectional associations between sleep and chronic low back pain.

Differences and Correlations of Anxiety, Sleep Quality, and Pressure-Pain Threshold between Patients with Chronic Low Back Pain and Asymptomatic People

Background. Chronic low back pain (CLBP) is a clinically common and expensive disease. Patients frequently take sick leaves because of pain and dysfunction, and their unpleasant life and work experiences cause psychological depression and anxiety and affect their quality of life. Sleep disturbance is a common problem among patients with low back pain (LBP) with more than 50% complaining about poor sleep quality. This study aimed to explore the correlations between anxiety, sleep quality, and pressure-pain threshold (PPT) and their differences between patients with CLBP and asymptomatic people. Methods. Forty patients with CLBP and 40 asymptomatic people were recruited. Relevant data, including State-Trait Anxiety Inventory, Pittsburgh Sleep Quality Index, and PPT, were individually and independently collected by blinded physiotherapists with a practicing certificate and then statistically analyzed. An independent sample t-test was used to determine the intergroup differences between patients with CLBP and asymptomatic populations. Pearson correlation coefficient was employed for correlation analysis. Results. The CLBP group had significantly higher anxiety scores (41.64 ± 9.88 vs. 36.69 ± 8.31; t = −2.496, $p=0.015$ ) than the asymptomatic group. A significant difference was found in the total score of the Pittsburgh Sleep Quality Index (6.41 ± 2.43 vs. 5.09 ± 2.18; t = −2.628, $p=0.010$ ) but not in the trait anxiety (44.00 ± 7.83 vs. 42.67 ± 9.51; t = −0.695, $p=0.489$ ) of the two groups. State−Trait Anxiety Inventory showed a low to moderate negative correlation with PPT. No remarkable correlation was observed between Pittsburgh Sleep Quality Index and PPT. Conclusions. Patients with CLBP showed considerably worse state anxiety and sleep quality than asymptomatic people; however, no substantial difference in PPT was found between the two groups. The results suggest that in clinical practice, the focus should include pain and related social and psychological factors. CLBP treatment could be considered from multiple perspectives and disciplines.This trial is registered with Chinese Clinical Trial Registry (Trial registration: ChiCTR-TRC-13003701).

Association of sleep quality status with worsening low back or knee pain during the COVID-19 state of emergency among old-old adults

Background

Poor sleep quality has a negative effect on pain among older adults. During the coronavirus disease 2019 (COVID-19) state of emergency, lifestyle changes can cause psychologic stressors and lead to poor sleep quality.

Aim

This study examined whether sleep quality status was associated with low back or knee pain changes during the COVID-19 state of emergency among community-dwelling Japanese old-old adults.

Design

Cross-sectional investigation.

Methods

In July 2020, during the COVID-19 epidemic, we conducted a postal survey for old-old adults aged ≥77 years and collected data on 597 participants. For those who had low back or knee pain at the time of the survey (in July), characteristics such as low back pain, knee pain, changes in pain status, and sleep quality status during the COVID-19 state of emergency (in March) were assessed.

Results

Data from 597 participants showed the prevalence of low back pain (50.6%) and knee pain (40.7%) in July. Of those with low back or knee pain, 374 had pain changes during the state of emergency, with 12.3% worsening. Of these, 23.9% had poor sleep quality in March compared to non-change (p = .008). In a multivariate logistic regression model adjusted for potential confounders, poor sleep quality was significantly associated with pain worsening (odds ratio 2.80, 95% confidence interval 1.26-6.22).

Conclusions

During the COVID-19 state of emergency, poor sleep quality was associated with worsening low back or knee pain. This may indicate the need to pay attention to poor sleep quality to prevent the exacerbation of pain among old-old adults.

The effect of sleep deprivation on empathy for pain: An ERP study

Empathy for pain has a strong adaptive function. It plays a protective role in survival and exerts a vital impact on successful social interaction. Sleep loss, however, is commonplace in current society, and people are increasingly plagued by it. Previous studies have investigated whether sleep loss affects empathy for pain, yet the results were undecided. We aimed to determine whether this effect is existed and further explore the temporal and frequency dynamics of neural activities involved in this effect by recording the electroencephalogram (EEG) signals. We recruited 25 healthy adults (11 females) who were required to perform a pain judgement and unpleasantness rating about the presented nociceptive and neutral pictures after nocturnal sleep (NS) and sleep deprivation (SD), and their neuronal activities were recorded by event-related potentials (ERPs). Results showed a significantly decreased amplitude in the early components (N2, N340) of vicarious pain processing after SD. In further time-frequency (TF) analysis, a reduced energy occurred in theta2 (5-7 Hz) band under SD condition. Moreover, the decreased theta2 was positively correlated with the subjective ratings of both other's pain and self-unpleasantness only under SD condition. Our results indicated that SD impairs affective sharing of empathy for pain.

Why It Is Important to Consider the Effects of Analgesics on Sleep: A Critical Review

We review the known physiological mechanisms underpinning all of pain processing, sleep regulation, and pharmacology of analgesics prescribed for chronic pain. In particular, we describe how commonly prescribed analgesics act in sleep-wake neural pathways, with potential unintended impact on sleep and/or wake function. Sleep disruption, whether pain- or drug-induced, negatively impacts quality of life, mental and physical health. In the context of chronic pain, poor sleep quality heightens pain sensitivity and may affect analgesic function, potentially resulting in further analgesic need. Clinicians already have to consider factors including efficacy, abuse potential, and likely side effects when making analgesic prescribing choices. We propose that analgesic-related sleep disruption should also be considered. The neurochemical mechanisms underlying the reciprocal relationship between pain and sleep are poorly understood, and studies investigating sleep in those with specific chronic pain conditions (including those with comorbidities) are lacking. We emphasize the importance of further work to clarify the effects (intended and unintended) of each analgesic class to inform personalized treatment decisions in patients with chronic pain. © 2021 American Physiological Society. Compr Physiol 11:1-31, 2021.

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

BACKGROUND

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

OBJECTIVE

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

DESIGN

Individual, randomized, controlled experimental study.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Sleep disturbance predicts future health status after stroke

STUDY OBJECTIVES

We evaluated factors associated with the presence of sleep disturbance in patients with stroke and whether sleep disturbance predicted change in other patient-reported domains of health over time.

METHODS

Observational cohort study of 2,190 patients with stroke seen in a cerebrovascular clinic February 17, 2015 to July 5, 2017 who completed patient-reported outcome measures (PROMs) at ≥ 1 visit, including the Patient Health Questionnaire-9 depression screen, Quality of Life in Neurological Disorders (NeuroQoL) cognitive function and Patient-Reported Outcomes Information Measurement System (PROMIS) sleep disturbance, fatigue, anxiety, social role satisfaction, physical function, and pain interference. Separate multivariable models were constructed with PROMIS sleep disturbance as the dependent variable. Covariates included clinical and demographic variables, the Patient Health Questionnaire-9 depression screen scored on the PROMIS metric, and 1 of the 6 other PROMs. Among the 476 patients with ≥ 2 visits, linear regression models were constructed to determine the association of baseline sleep disturbance with follow-up PROMs after adjustment for the corresponding baseline PROMIS/NeuroQol scores, depression score, and clinical variables.

RESULTS

Younger age and all PROM scores were associated with sleep disturbance; depression had the greatest association among PROMs (beta estimate 0.53, 95% confidence interval, 0.49, 0.57), physical function had the least (-0.06, 95% confidence interval, -0.11, -0.01). Baseline PROMIS sleep disturbance score was associated with worse adjusted follow-up scores for depression, fatigue, social role satisfaction, and physical function.

CONCLUSIONS

Younger age and all 8 PROMs were associated with sleep disturbance in patients with stroke. The degree of sleep disturbance predicted future patient-reported outcomes for multiple domains of health. Further study is warranted to determine if interventions shown to improve sleep symptoms will also improve other outcomes.

Long-term changes in self-reported sleep quality and risk of chronic musculoskeletal pain: The HUNT Study

We examined the association between long-term (~10 years) changes in self-reported sleep quality and risk of any chronic musculoskeletal pain and chronic widespread pain. The study comprised data on 6,033 people who participated in three consecutive surveys in the Norwegian HUNT Study (1995-1997, 2006-2008 and 2017-2019) and who were without chronic musculoskeletal pain at the first two surveys. We used a modified Poisson regression model to calculate adjusted risk ratios for chronic pain at follow-up (2017-2019) associated with categories of poor and good sleep quality reported in 1995-1997 and 2006-2008. Compared with people who reported good sleep at both surveys (crude absolute risk: 32.4%), the risk ratios of any chronic pain were 1.20 (95% confidence interval: 1.02-1.41) for those who changed from poor to good sleep; 1.25 (95% confidence interval: 1.12-1.39) for those who changed from good to poor sleep; and 1.41 (95% confidence interval: 1.21-1.63) for those who reported long-term poor sleep. The corresponding risk ratios for chronic widespread pain were 1.35 (95% confidence interval: 0.82-2.23), 1.55 (95% confidence interval: 1.14-2.12) and 2.09 (95% confidence interval: 1.38-3.17), respectively. In conclusion, these findings indicate that people with long-term poor sleep quality have a markedly higher risk of chronic musculoskeletal pain and chronic widespread pain, compared with people who remain good sleep quality.

Fibromyalgia: Pathogenesis, Mechanisms, Diagnosis and Treatment Options Update

Fibromyalgia is a syndrome characterized by chronic and widespread musculoskeletal pain, often accompanied by other symptoms, such as fatigue, intestinal disorders and alterations in sleep and mood. It is estimated that two to eight percent of the world population is affected by fibromyalgia. From a medical point of view, this pathology still presents inexplicable aspects. It is known that fibromyalgia is caused by a central sensitization phenomenon characterized by the dysfunction of neuro-circuits, which involves the perception, transmission and processing of afferent nociceptive stimuli, with the prevalent manifestation of pain at the level of the locomotor system. In recent years, the pathogenesis of fibromyalgia has also been linked to other factors, such as inflammatory, immune, endocrine, genetic and psychosocial factors. A rheumatologist typically makes a diagnosis of fibromyalgia when the patient describes a history of pain spreading in all quadrants of the body for at least three months and when pain is caused by digital pressure in at least 11 out of 18 allogenic points, called tender points. Fibromyalgia does not involve organic damage, and several diagnostic approaches have been developed in recent years, including the analysis of genetic, epigenetic and serological biomarkers. Symptoms often begin after physical or emotional trauma, but in many cases, there appears to be no obvious trigger. Women are more prone to developing the disease than men. Unfortunately, the conventional medical therapies that target this pathology produce limited benefits. They remain largely pharmacological in nature and tend to treat the symptomatic aspects of various disorders reported by the patient. The statistics, however, highlight the fact that 90% of people with fibromyalgia also turn to complementary medicine to manage their symptoms.

Effect of Telephone Cognitive Behavioral Therapy for Insomnia in Older Adults With Osteoarthritis Pain: A Randomized Clinical Trial

IMPORTANCE

Scalable delivery models of cognitive behavioral therapy for insomnia (CBT-I), an effective treatment, are needed for widespread implementation, particularly in rural and underserved populations lacking ready access to insomnia treatment.

OBJECTIVE

To evaluate the effectiveness of telephone CBT-I vs education-only control (EOC) in older adults with moderate to severe osteoarthritis pain.

DESIGN, SETTING, AND PARTICIPANTS

This is a randomized clinical trial of 327 participants 60 years and older who were recruited statewide through Kaiser Permanente Washington from September 2016 to December 2018. Participants were double screened 3 weeks apart for moderate to severe insomnia and osteoarthritis (OA) pain symptoms. Blinded assessments were conducted at baseline, after 2 months posttreatment, and at 12-month follow-up.

INTERVENTIONS

Six 20- to 30-minute telephone sessions provided over 8 weeks. Participants submitted daily diaries and received group-specific educational materials. The CBT-I instruction included sleep restriction, stimulus control, sleep hygiene, cognitive restructuring, and homework. The EOC group received information about sleep and OA.

MAIN OUTCOMES AND MEASURES

The primary outcome was score on the Insomnia Severity Index (ISI) at 2 months posttreatment and 12-month follow-up. Secondary outcomes included pain (score on the Brief Pain Inventory-short form), depression (score on the 8-item Patient Health Questionnaire), and fatigue (score on the Flinders Fatigue Scale).

RESULTS

Of the 327 participants, the mean (SD) age was 70.2 (6.8) years, and 244 (74.6%) were women. In the 282 participants with follow-up ISI data, the total 2-month posttreatment ISI scores decreased 8.1 points in the CBT-I group and 4.8 points in the EOC group, an adjusted mean between-group difference of -3.5 points (95% CI, -4.4 to -2.6 points; P < .001). Results were sustained at 12-month follow-up (adjusted mean difference, -3.0 points; 95% CI, -4.1 to -2.0 points; P < .001). At 12-month follow-up, 67 of 119 (56.3%) participants receiving CBT-I remained in remission (ISI score, ≤7) compared with 33 of 128 (25.8%) participants receiving EOC. Fatigue was also significantly reduced in the CBT-I group compared with the EOC group at 2 months posttreatment (mean between-group difference, -2.0 points; 95% CI, -3.1 to -0.9 points; P = <.001) and 12-month follow-up (mean between-group difference, -1.8 points; 95% CI, -3.1 to -0.6 points; P = .003). Posttreatment significant differences were observed for pain, but these differences were not sustained at 12-month follow-up.

CONCLUSIONS AND RELEVANCE

In this randomized clinical trial, telephone CBT-I was effective in improving sleep, fatigue, and, to a lesser degree, pain among older adults with comorbid insomnia and OA pain in a large statewide health plan. Results support provision of telephone CBT-I as an accessible, individualized, effective, and scalable insomnia treatment.

TRIAL REGISTRATION

Clinical Trials.gov Identifier: NCT02946957.

Experimental sleep restriction increases latency jitter in pain elicited cortical responses

Objective

Previous studies have shown increased pain scores to painful stimulation after experimental sleep restriction, but reduced or unchanged magnitude of the event related potentials (ERPs) when averaged in the time-domain. However, some studies found increased response magnitude when averaging in the time-frequency domain. The aim of this study was to determine whether ERP-latency jitter may contribute to this discrepancy.

Methods

Ninety painful electrical stimuli were given to 21 volunteers after two nights of 50% sleep restriction and after two nights of habitual sleep. ERPs were analyzed in the time-domain (N2-and P2-peaks) and time-frequency domain (power spectral density). We quantified latency jitter by the mean consecutive difference (MCD) between single-trial peak latencies and by phase locking value (PLV) across trials.

Results

P2-MCD increased from 20.4 ± 2.1 ms after habitual sleep to 24.3 ± 2.2 ms after sleep restriction (19%, p = 0.038) and PLV decreased from 0.582 ± 0.015 after habitual sleep to 0.536 ± 0.015 after sleep restriction (7.9%, p = 0.009). We found no difference for N2-MCD.

Conclusions

Our results indicate that partial sleep restriction increase latency jitter in cortical responses to experimental pain.

Significance

Latency jitter may contribute to the discrepancies between ERP-responses in the time-frequency domain and time-domain. Latency jitter should be considered when ERPs are analyzed.

Positive Encounters as a Buffer: Pain and Sleep Disturbances in Older Adults' Everyday Lives

Objectives: To test whether older adults' pain was bidirectionally associated with nighttime sleep disturbances and whether daily positive encounters attenuated these associations. Methods: Participants (N = 292, mean = 73.71 years old) from the Daily Experiences and Well-being Study indicated pain and positive encounters with close partners (e.g., family and friends) and nonclose partners (e.g., acquaintances and service providers) every 3 hours throughout each day across 4-6 days. They also reported nighttime sleep disturbances the following morning. Results: Multilevel models revealed that participants with more prior nighttime sleep disturbances reported more severe pain the next day. This link was attenuated on days when participants had a greater proportion of positive encounters or viewed encounters as more pleasant, especially when these encounters occurred with close partners. Discussion: This study identifies benefits of positive encounters to older adults and sheds light on ways that may alleviate their pain from a social perspective.

Prevalence of low back pain in young Brazilians and associated factors: Sex, physical activity, sedentary behavior, sleep and body mass index

BACKGROUND

Low back pain (LBP) has become increasingly common, but the prevalence of this complaint and associated factors in young people remains controversial.

OBJECTIVE

This study aimed to identify the prevalence of LBP and to explore the existence of associated factors (sex, physical activity, sedentary lifestyle, sleep, body mass index and waist circumference).

METHODS

This study considered all complaints of the lumbar region (acute or chronic) as LBP, which can irradiate to the backside and legs, lasting a minimum of 24 hours. Youngsters aged 15 to 18 years from a school in the south of Brazil were evaluated. Descriptive statistics was used, in particular Chi-square, Mann-Whitney U tests and binary logistic regression. A significance level of p< 0.05 was adopted.

RESULTS

A total of 330 youngsters answered a questionnaire and had their anthropometric measurements measured (response rate 84%). The prevalence of LBP in the present was 30%, quarterly 63% and throughout life 77%. There was a significant association between LBP and sex: girls have an increased risk of LBP in the last three-month period (PR = 1.3, 95% CI 1.06-1.56) and throughout life (PR = 1.2, 95% CI 1.04-1.43). The practice of physical activities was also associated with LBP, but as a protection factor in the present and in the last three-month period (PR = 0.7, 95% CI 0.47-0.90). Physical education at school has demonstrated a protective factor regarding LBP throughout life (PR = 0.9, 95% CI 0.77-0.97). Most of the students did not comply with recommendations related to sleep and time spent doing activities in front of a screen, and no association of these factors with LBP was detected. This exposure (physical activity, sleep time, sedentarism) did not present significant association with LBP when adjusted by the confusion factors (sex, age, BMI).

CONCLUSIONS

Youngsters reported a high prevalence of LBP. Girls were at greater risk of LBP than boys. It is recommended that prevention strategies focus on the practices of physical activities and scholar physical education. No association of LBP with sedentary lifestyle (TV and computer use time, sleep time), anthropometric measures and sleeping duration was observed.

Relationships Between Psychological, Sleep, and Physical Activity Measures and Somatosensory Function in People With Peripheral Joint Pain: A Systematic Review and Meta-Analysis

OBJECTIVE

Alteration in somatosensory function has been linked to pain experience in individuals with joint pain. In this systematic review we aimed to establish the level of evidence of associations between psychological, social, physical activity, and sleep measures and somatosensory function that were assessed via quantitative sensory testing (QST) among individuals with joint pain.

METHODS

A comprehensive literature search was conducted in 6 electronic databases from their inception to July 2019. Two reviewers independently assessed the methodological quality using a modified Quality in Prognostic Studies (QUIPS) tool and supplemented with recommendations from the Critical Appraisal and Data Extraction for Systematic Review of Prediction Modelling Studies (CHARMS) checklist and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. The level of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) system. Data were pooled to evaluate the strength of the relationships of interest.

RESULTS

Seventeen studies related to joint pain were included. Pain catastrophizing, depression, anxiety, and physical activity level have been shown to have a significant (small to fair) association with several QST measures. Pressure pain threshold (PPT) is the only measure that was found to be consistently correlated with all the domains. The overall quality of evidence for all factors ranged from very low to moderate. Subgroup analysis revealed a stronger association for depression and pain catastrophizing and PPT and temporal pain summation in individuals with shoulder pain.

CONCLUSION

Psychological factors and physical activity levels are associated with somatosensory function in people with joint pain. These factors need to be adjusted when establishing predictive relationships between somatosensory function and pain outcomes in individuals with joint pain.

Sleep disturbance as a moderator of the association between physical activity and later pain onset among American adults aged 50 and over: evidence from the Health and Retirement Study

OBJECTIVE

To examine whether sleep disturbance modifies the association between physical activity and incident pain.

DESIGN

Prospective population-based study.

SETTING

Health and Retirement Study.

PARTICIPANTS

American adults aged ≥50 years who reported no troublesome pain in 2014 were re-assessed for pain in 2016. Of 9828 eligible baseline respondents, 8036 (82%) had complete follow-up data for adjusted analyses (weighted analysis population N=42 407 222).

EXPOSURES

Physical activity was assessed via interview with questions about time spent in moderate and vigorous physical activity. Sleep disturbance, assessed using a modified form of the Jenkins Sleep Scale, was examined as a potential moderator.

MAIN OUTCOME MEASURE

Troublesome pain.

RESULTS

In weighted analyses, 37.9% of the 2014 baseline pain-free sample participated in moderate or vigorous physical activity once a week or less, with an overall mean Physical Activity Index Score of 9.0 (SE=0.12). 18.6% went on to report troublesome pain in 2016. Each one-point higher on the Physical Activity Index Score was associated with a reduced odds ratio (OR) of incident pain for those who endorsed sleep disturbance never/rarely (OR=0.97, 95% CI 0.94 to 0.99), but not for those who endorsed sleep disturbance sometimes (OR=0.99, 95% CI 0.97 to 1.01) or most of the time (OR=1.01, 95% CI 0.99 to 1.03). The analysis of possible interaction demonstrated that frequency of sleep disturbance moderated the physical activity and incident pain association (Wald test: p=0.02).

CONCLUSIONS

The beneficial association of physical activity on reduced likelihood of later pain was only observed in persons who endorsed low levels of sleep disturbance.

Less Pain, Better Sleep? The Effect of a Multidisciplinary Back Pain App on Sleep Quality in Individuals Suffering from Back Pain - a Secondary Analysis of App User Data

Purpose

Mobile health solutions are finding their way into health systems. The Kaia app has been shown to be able to reduce back pain in two studies. Since pain often comes along with disturbed sleep and both symptoms are strongly related we investigated whether the Kaia app training is associated with improved sleep quality.

Methods

User data of individuals with back pain were collected in two app versions (cohort 1: N = 180; cohort 2: N = 159). We analyzed the ratings of sleep quality and pain intensity on a 11-point numeric ratings scale (NRS; 0–10) both at the beginning of usage (baseline: BL) and on the individual last day of usage (follow-up: LU) within a 3-month training program.

Results

In both cohorts, we found a significant reduction in pain intensity from BL to LU (cohort 1: M_BL = 4.80; SD = 1.59 to M_LU = 3.75; SD = 1.76, Δ_pain = –1.04; SD = 2.12; t(158) = 6.207; p<.001/cohort 2: M_BL = 4.20; SD = 1.98 to M_LU = 3.65; SD = 1.78; Δ_pain = –0.50; SD = 2.04; t(147) = 3.001; p = 0.003) and a significant improvement of sleep quality (cohort 1: M_BL = 5.76; SD = 2.12 to M_LU = 6.56; SD = 1.72; Δ_sleep = t(158) = 4.310; p < 0.001/cohort 2: M_BL = 6.08; SD = 2.08 to M_LU = 6.76; SD = 1.55; Δ_sleep = 0.67; SD = 2.13; sleep: t(147) = 3.825; p < 0.001). Interestingly, improvement of sleep quality was not fully mediated by pain reduction.

Conclusion

Our analysis underlines the relationship between pain and sleep in the clinical context. Improvement of sleep quality came along with pain reduction and vice versa. Further study should explain the exact mechanisms of action which are associated with the improvement of both symptom parameters.

Number of Chronic Nighttime Insomnia Symptoms and Risk of Chronic Widespread Pain and Pain-Related Disability: The HUNT Study

STUDY OBJECTIVES

To examine the association between the number of chronic nighttime insomnia symptoms and the risk of chronic widespread pain (CWP) and pain-related disability.

METHODS

A prospective study of 10,847 participants in the Norwegian HUNT Study without chronic musculoskeletal pain at baseline in 2006-2008. We used a modified Poisson regression model to estimate adjusted risk ratios (RRs) with a 95% confidence interval (CI) for CWP and pain-related disability at follow-up in 2017-2019 associated with insomnia and number of nighttime insomnia symptoms at baseline. Chronic insomnia was defined according to the current classification system and grouped into three categories based on the number of reported nighttime symptoms (ie, difficulty initiating sleep, trouble maintaining sleep and early morning awakenings).

RESULTS

Compared to the reference group of people without insomnia, people with insomnia had RRs for CWP and pain-related disability of 1.64 (1.26-2.14) and 1.63 (1.37-1.94), respectively. When people with insomnia were categorized based on the number of nighttime symptoms, people who reported one, two, or three nighttime symptoms had RRs of CWP of 1.19 (95% CI 0.80-1.78), 1.78 (95 CI 1.13-2.80) and 3.08 (95% CI 1.93-4.92), respectively, compared to people without insomnia. The corresponding RRs for pain-related disability were 1.49 (95% CI 1.17-1.89), 1.46 (95% CI 2.04-2.05), and 2.46 (95% CI 1.76-3.42).

CONCLUSION

These findings indicate that people with insomnia characterized by symptoms in all phases of the sleep period have a substantially increased risk of CWP and pain-related disability.

Sleep deprivation of rats increases postsurgical expression and activity of L-type calcium channel in the dorsal root ganglion and slows recovery from postsurgical pain

Perioperative sleep disturbance is a risk factor for persistent pain after surgery. Clinical studies have shown that patients with insufficient sleep before and after surgery experience more intense and long-lasting postoperative pain. We hypothesize that sleep deprivation alters L-type calcium channels in the dorsal root ganglia (DRG), thus delaying the recovery from post-surgical pain. To verify this hypothesis, and to identify new predictors and therapeutic targets for persistent postoperative pain, we first established a model of postsurgical pain with perioperative sleep deprivation (SD) by administering hind paw plantar incision to sleep deprivation rats. Then we conducted behavioral tests, including tests with von Frey filaments and a laser heat test, to verify sensory pain, measured the expression of L-type calcium channels using western blotting and immunofluorescence of dorsal root ganglia (an important neural target for peripheral nociception), and examined the activity of L-type calcium channels and neuron excitability using electrophysiological measurements. We validated the findings by performing intraperitoneal injections of calcium channel blockers and microinjections of dorsal root ganglion cells with adeno-associated virus. We found that short-term sleep deprivation before and after surgery increased expression and activity of L-type calcium channels in the lumbar dorsal root ganglia, and delayed recovery from postsurgical pain. Blocking these channels reduced impact of sleep deprivation. We conclude that the increased expression and activity of L-type calcium channels is associated with the sleep deprivation-mediated prolongation of postoperative pain. L-type calcium channels are thus a potential target for management of postoperative pain.

Influence of sleep problems and co-occurring musculoskeletal pain on long-term prognosis of chronic low back pain: the HUNT Study

Background

We investigated the influence of sleeplessness and number of insomnia symptoms on the probability of recovery from chronic low back pain (LBP), and the possible interplay between sleeplessness and co-occurring musculoskeletal pain on this association.

Methods

The study comprised data on 3712 women and 2488 men in the Norwegian HUNT study who reported chronic LBP at baseline in 1995–1997. A modified Poisson regression model was used to calculate adjusted risk ratios (RRs) for the probability of recovery from chronic LBP at follow-up in 2006–2008, associated with sleep problems and co-occurring musculoskeletal pain at baseline.

Results

Compared with persons without sleeplessness, persons who often/always experienced sleeplessness had a lower probability of recovery from chronic LBP (RR 0.65, 95% CI 0.57 to 0.74 in women and RR 0.81, 95% CI 0.69 to 0.95 in men). Although there was no clear evidence of statistical interaction between sleeplessness and co-occurring musculoskeletal pain, women and men who often/always experienced sleeplessness and had ≥5 additional chronic pain sites had RRs of recovery of 0.40 (95% CI 0.33 to 0.48) and 0.59 (95% CI 0.45 to 0.78), respectively, compared with persons without sleeplessness and 1–2 chronic pain sites.

Conclusion

These findings suggest that preventing or reducing sleep problems among people with chronic LBP may have the potential of improving the long-term prognosis of this condition, also among those with several additional pain sites.

Relationships Between Psychological, Social, Physical Activity, and Sleep Measures and Somatosensory Function in Individuals With Spinal Pain: A Systematic Review and Meta-analysis

OBJECTIVE

Somatosensory abnormalities are linked to clinical pain outcomes in individuals with spinal pain. However, a range of factors might confound the relationship between altered somatosensory function and clinical pain outcomes. This systematic review aimed to evaluate the literature to assess the level of evidence of associations between psychological, social, physical activity, and sleep measures and somatosensory function (assessed via sensory psychophysical testing) among individuals with spinal pain.

METHODS

A comprehensive literature search was performed in 6 electronic databases from their inception to June 2018. Two reviewers independently assessed the methodological quality using a modified Quality in Prognostic Studies (QUIPS) tool and supplemented with recommendations from the Critical Appraisal and Data Extraction for the Systematic Review of Prediction Modelling Studies (CHARMS) checklist and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. The level of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) system. Data were pooled to evaluate the strength of the relationships of interest.

RESULTS

Among the 17 factors identified in the included studies, pain catastrophizing, depression, and pain-related fear have significant negative (small to fair) associations with pain thresholds. A "very low" to "moderate" quality of evidence was found for all the investigated factors. Subgroup analysis showed a smaller effect size for pain catastrophizing/fear of movement and pain thresholds in individuals with low back pain.

CONCLUSIONS

Psychological factors are associated negatively with pain thresholds and they need to be adjusted when establishing predictive relationships between somatosensory function and pain outcomes in individuals with spinal pain.

PER3 variable number tandem repeat (VNTR) polymorphism modulates the circadian variation of the descending pain modulatory system in healthy subjects

We evaluated the circadian pattern of variation of the descending pain modulatory system (DPMS) using a conditioned pain modulation (CPM) paradigm according to the variable-number tandem-repeat (VNTR) of the clock gene PER3 polymorphism. We assessed the relationship between the genotypes PER3^4/4 and PER3^5/5 and the temporal pattern of variation across the day using the following measures: the heat pain threshold (HPT), the cold pressure test (CPT), and the serum levels of BDNF and S100-B protein. The ∆-values (from afternoon to morning) of these measures were used for the analysis. The circadian phenotype was according to the mid-point sleep time established by the Munich ChronoType Questionnaire (MCTQ). We included 18 healthy volunteers (15 women) ages 18 to 30. A Generalized Linear Model (GLM) revealed a significant difference in the ∆-CPM-task between Per3^4/4 and Per3^5/5 genotypes, with means (SDs) of -0.41 (0.78) vs. 0.67 (0.90) (χ² = 7.256; df = 1' P = 0.007), respectively. Both sleep deprivation of at least 2 h/day (B = -0.96, 95% confidence interval (CI) = -1.86 to -0.11)) and the ∆-S100-B protein (-0.03, 95% CI = -0.06 to -0.02) were negatively correlated with the ∆-CPM-task, while the ∆-BDNF was positively correlated with the ∆-CPM-task (0.015, 95% CI = 0.01 to 0.03). We observed a difference in the ∆-CPT between PER3^4/4 and PER3^5/5 (0.11 (4.51) vs. 4.00 (2.60), respectively) (χ² = 22.251; df = 1 P = 0.001). These findings suggest that the polymorphism of PER3^5/5 is associated with a decrease in the inhibitory function of the DPMS over the course of the day. However, sleep deprivation is an independent factor that also reduces the inhibitory function of the DPMS, regardless of the PER3 VNTR polymorphism.

Chronic exposure to insufficient sleep alters processes of pain habituation and sensitization

Chronic pain conditions are highly comorbid with insufficient sleep. While the mechanistic relationships between the 2 are not understood, chronic insufficient sleep may be 1 pathway through which central pain-modulatory circuits deteriorate, thereby contributing to chronic pain vulnerability over time. To test this hypothesis, an in-laboratory model of 3 weeks of restricted sleep with limited recovery (5 nights of 4-hour sleep per night followed by 2 nights of 8-hour sleep per night) was compared with 3 weeks of 8-hour sleep per night (control protocol). Seventeen healthy adults participated, with 14 completing both 3-week protocols. Measures of spontaneous pain, heat-pain thresholds, cold-pain tolerance (measuring habituation to cold over several weeks), and temporal summation of pain (examining the slope of pain ratings during cold water immersion) were assessed at multiple points during each protocol. Compared with the control protocol, participants in the sleep-restriction protocol experienced mild increases in spontaneous pain (P < 0.05). Heat-pain thresholds decreased after the first week of sleep restriction (P < 0.05) but normalized with longer exposure to sleep restriction. By contrast, chronic exposure to restricted sleep was associated with decreased habituation to, and increased temporal summation in response to cold pain (both P < 0.05), although only in the past 2 weeks of the sleep-restriction protocol. These changes may reflect abnormalities in central pain-modulatory processes. Limited recovery sleep did not completely resolve these alterations in pain-modulatory processes, indicating that more extensive recovery sleep is required. Results suggest that exposure to chronic insufficient sleep may increase vulnerability to chronic pain by altering processes of pain habituation and sensitization.

Chronic Pain and Chronic Opioid Use After Intensive Care Discharge - Is It Time to Change Practice?

Almost half of patients treated on intensive care unit (ICU) experience moderate to severe pain. Managing pain in the critically ill patient is challenging, as their pain is complex with multiple causes. Pharmacological treatment often focuses on opioids, and over a prolonged admission this can represent high cumulative doses which risk opioid dependence at discharge. Despite analgesia the incidence of chronic pain after treatment on ICU is high ranging from 33-73%. Measures need to be taken to prevent the transition from acute to chronic pain, whilst avoiding opioid overuse. This narrative review discusses preventive measures for the development of chronic pain in ICU patients. It considers a number of strategies that can be employed including non-opioid analgesics, regional analgesia, and non-pharmacological methods. We reason that individualized pain management plans should become the cornerstone for critically ill patients to facilitate physical and psychological well being after discharge from critical care and hospital.

The Pain of Sleep Loss: A Brain Characterization in Humans

Sleep loss increases the experience of pain. However, the brain mechanisms underlying altered pain processing following sleep deprivation are unknown. Moreover, it remains unclear whether ecologically modest night-to-night changes in sleep, within an individual, confer consequential day-to-day changes in experienced pain. Here, we demonstrate that acute sleep deprivation amplifies pain reactivity within human (male and female) primary somatosensory cortex yet blunts pain reactivity in higher-order valuation and decision-making regions of the striatum and insula cortex. Consistent with this altered neural signature, we further show that sleep deprivation expands the temperature range for classifying a stimulus as painful, specifically through a lowering of pain thresholds. Moreover, the degree of amplified reactivity within somatosensory cortex following sleep deprivation significantly predicts this expansion of experienced pain across individuals. Finally, outside of the laboratory setting, we similarly show that even modest nightly changes in sleep quality (increases and decreases) within an individual determine consequential day-to-day changes in experienced pain (decreases and increases, respectively). Together, these data provide a novel framework underlying the impact of sleep loss on pain and, furthermore, establish that the association between sleep and pain is expressed in a night-to-day, bidirectional relationship within a sample of the general population. More broadly, our findings highlight sleep as a novel therapeutic target for pain management within and outside the clinic, including circumstances where sleep is frequently short yet pain is abundant (e.g., the hospital setting).SIGNIFICANCE STATEMENT Are you experiencing pain? Did you have a bad night of sleep? This study provides underlying brain and behavioral mechanisms explaining this common co-occurrence. We show that sleep deprivation enhances pain responsivity within the primary sensing regions of the brain's cortex yet blunts activity in other regions that modulate pain processing, the striatum and insula. We further establish that even subtle night-to-night changes in sleep in a sample of the general population predict consequential day-to-day changes in pain (bidirectionally). Considering the societal rise in chronic pain conditions in lock-step with the decline in sleep time through the industrial world, our data support the hypothesis that these two trends may not simply be co-occurring but are significantly interrelated.

Effect of sleep restriction on somatosensory sensitivity including occlusal sensation in the orofacial area

PURPOSE

To investigate the effect of sleep restriction on somatosensory sensitivity related to occlusion.

METHODS

Twelve healthy participants participated in an experimental voluntary total sleep restriction (SR) study. In a study design, they were invited to sleep as usual, normal sleep (NS) or to restrict their sleep for four nights. Following the SR night, participants were followed for 3 consecutive days including the 2 sleep nights. In NS experiment, all participants were instructed to maintain NS both nights. During all nights, actigraphy data were collected and total sleep time was estimated. On days before and after sleep conditions, all participants underwent measurements of tactile detection threshold (TDT), interocclusal detection threshold (IDT), perception of unpleasantness (POU), and the Epworth sleepiness scale (ESS).

RESULTS

As expected, total sleep time on the first night in SR experiment was significantly shorter than on the second night in SR experiment and on the first night in NS experiment (P<0.05). ESS values on Day-2 following SR experiment were significantly higher than on Day-1 and Day-3 in SR experiment and Day-2 in NS experiment (P<0.05). There were no significant differences in TDT and IDT between each day at each measurement point in both experiments. POU was significantly lower on Day-2 in SR experiment than on Day-1 and Day-3 in SR experiment and on Day-2 in NS experiment (P<0.05).

CONCLUSIONS

The present results suggest that SR affects to occlusal sensation related to POU.

Pain and sleep : A bidirectional relationship

Disturbed sleep and persistent pain are common in old people. Persistent pain has a well proven impact on sleep but the relationship between both phenomena is bidirectional since disturbed sleep affects pain perception by lowering the pain threshold. An optimal disease management takes both phenomena into account.

Chronic sleep restriction increases pain sensitivity over time in a periaqueductal gray and nucleus accumbens dependent manner

Painful conditions and sleep disturbances are major public health problems worldwide and one directly affects the other. Sleep loss increases pain prevalence and severity; while pain disturbs sleep. However, the underlying mechanisms are largely unknown. Here we asked whether chronic sleep restriction for 6 h daily progressively increases pain sensitivity and if this increase is reversed after two days of free sleep. Also, whether the pronociceptive effect of chronic sleep restriction depends on the periaqueductal grey and on the nucleus accumbens, two key regions involved in the modulation of pain and sleep-wake cycle. We showed that sleep restriction induces a pronociceptive effect characterized by a significant decrease in the mechanical paw withdrawal threshold in rats. Such effect increases progressively from day 3 to day 12 remaining stable thereafter until day 26. Two consecutive days of free sleep were not enough to reverse the effect, not even to attenuate it. This pronociceptive effect depends on the periaqueductal grey and on the nucleus accumbens, since it was prevented by their excitotoxic lesion. Complementarily, chronic sleep restriction significantly increased c-Fos protein expression within the periaqueductal grey and the nucleus accumbens and this correlates with the intensity of the pronociceptive effect, suggesting that the greater the neural activity in this regions, the greater the effect. These findings may contribute not only to understand why painful conditions are more prevalent and severe among people who sleep poorly, but also to develop therapeutic strategies to prevent this, increasing the effectiveness of pain management in this population.

Bidirectional association between disturbed sleep and neuropathic pain symptoms: a prospective cohort study in post-total joint replacement participants

Background

Disturbed sleep is strongly correlated with chronic pain. The aim of this study was to examine the association between sleep disturbance and incident joint pain focusing on neuropathic-like pain symptoms.

Methods

A total of 423 individuals who had undergone total joint replacement (TJR) for osteoarthritis were assessed at the mean time of 3.6 years post-surgery and again at 5.9 years post-TJR, using the Medical Outcomes Survey sleep subscale, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and painDETECT questionnaire instruments. Cox hazard ratios (HRs) and 95% confidence intervals (CIs) were computed adjusting for age, body mass index, sex, and use of hypnotic and analgesic medication.

Results

The presence of neuropathic pain symptoms predicted incidence of disturbed sleep after adjustment for covariates and pain severity (adjusted HR [aHR] 2.01, 95% CI: 1.00–4.10; p<0.05). There was no association between joint pain and incidence of disturbed sleep when individuals with neuropathic pain symptoms at the baseline visit were excluded (aHR 1.11, 95% CI: 0.47–2.67). Disturbed sleep at baseline predicted incident neuropathic joint pain symptoms (aHR 2.75, 95% CI: 1.21–6.26; p<0.016) but had no effect on incidence of joint pain when all types of pain were considered together (aHR 0.63, 95% CI: 0.30–1.39).

Conclusion

These data suggest a causal bidirectional link between sleep disturbance and joint pain with neuropathic features but not with other types of joint pain.

Habituation of phase-locked local field potentials and gamma-band oscillations recorded from the human insula

Salient nociceptive and non-nociceptive stimuli elicit low-frequency local field potentials (LFPs) in the human insula. Nociceptive stimuli also elicit insular gamma-band oscillations (GBOs), possibly preferential for thermonociception, which have been suggested to reflect the intensity of perceived pain. To shed light on the functional significance of these two responses, we investigated whether they would be modulated by stimulation intensity and temporal expectation - two factors contributing to stimulus saliency. Insular activity was recorded from 8 depth electrodes (41 contacts) implanted in the left insula of 6 patients investigated for epilepsy. Thermonociceptive, vibrotactile, and auditory stimuli were delivered using two intensities. To investigate the effects of temporal expectation, the stimuli were delivered in trains of three identical stimuli (S1-S2-S3) separated by a constant 1-s interval. Stimulation intensity affected intensity of perception, the magnitude of low-frequency LFPs, and the magnitude of nociceptive GBOs. Stimulus repetition did not affect perception. In contrast, both low-frequency LFPs and nociceptive GBOs showed a marked habituation of the responses to S2 and S3 as compared to S1 and, hence, a dissociation with intensity of perception. Most importantly, although insular nociceptive GBOs appear to be preferential for thermonociception, they cannot be considered as a correlate of perceived pain.