Musculoskeletal sensitization and sleep: chronic muscle pain fragments sleep of mice without altering its duration

STUDY OBJECTIVES

Musculoskeletal pain in humans is often associated with poor sleep quality. We used a model in which mechanical hypersensitivity was induced by injection of acidified saline into muscle to study the impact of musculoskeletal sensitization on sleep of mice.

DESIGN

A one month pre-clinical study was designed to determine the impact of musculoskeletal sensitization on sleep of C57BL/6J mice.

METHODS

We instrumented mice with telemeters to record the electroencephalogram (EEG) and body temperature. We used an established model of musculoskeletal sensitization in which mechanical hypersensitivity was induced using two unilateral injections of acidified saline (pH 4.0). The injections were given into the gastrocnemius muscle and spaced five days apart. EEG and body temperature recordings started prior to injections (baseline) and continued for three weeks after musculoskeletal sensitization was induced by the second injection. Mechanical hypersensitivity was assessed using von Frey filaments at baseline (before any injections) and on days 1, 3, 7, 14, and 21 after the second injection.

RESULTS

Mice injected with acidified saline developed bilateral mechanical hypersensitivity at the hind paws as measured by von Frey testing and as compared to control mice and baseline data. Sleep during the light period was fragmented in experimental mice injected with acidified saline, and EEG spectra altered. Musculoskeletal sensitization did not alter the duration of time spent in wakefulness, non-rapid eye movement sleep, or rapid eye movement sleep.

CONCLUSIONS

Musculoskeletal sensitization in this model results in a distinct sleep phenotype in which sleep is fragmented during the light period, but the overall duration of sleep is not changed. This study suggests the consequences of musculoskeletal pain include sleep disruption, an observation that has been made in the clinical literature but has yet to be studied using preclinical models.

[Impact of the fibromyalgia in the chronic fatigue syndrome]

BACKGROUND AND OBJECTIVE

Different studies have showed association of the chronic fatigue syndrome (CFS) with other pathologies, including fibromyalgia (FM). The objective of this study is to analyze whether there are differences in the clinic and in the assessment of fatigue in CFS patients associated or not with FM.

PATIENTS AND METHODS

A cross-sectional, single-site observational study was undertaken on a consecutive cases of a register of CFS patients at CFS Unit in Vall d'Hebron Hospital, Barcelona, from January 2008 until March 2011. The variables analyzed were FM comorbidity, sleep and fatigue characteristics and cognitive, neurological and autonomic symptoms. Questionnaires of fatigue impact scale, fatigue strength and impact on quality of life SF-36 were evaluated.

RESULTS

We included 980 CFS patients (mean age: 48±9 years; 91% women). Fibromyalgia was present in 528 patients (54%). The level of fatigue (P=.001) and pain (P<.001) was higher in FM patients. Patients with CFS and FM had more prevalence of sleep-related phenomena. The percentage of patients and the degree of severity of cognitive symptoms, neurological and autonomic dysfunction was higher in FM patients (P<.001). FM patients scored higher on the fatigue impact scale (P<.001) and showed worse results in the quality of life questionnaire (P<.001).

CONCLUSIONS

FM co-morbidity worse clinical parameters, fatigue and the perception of quality of life in CFS patients.

Comorbid insomnia in patients with chronic pain: a study based on the Swedish quality registry for pain rehabilitation (SQRP)

PURPOSE

This study investigates the prevalence of insomnia and its relationship to other symptoms and health aspects in patients with chronic pain.

METHODS

Patients with chronic pain conditions (n = 845) referred to a multidisciplinary pain centre completed surveys provided by the Swedish quality registry for pain rehabilitation (SQRP). The SQRP collects data on socio-demographics, health status, symptoms of pain, mood and insomnia and life satisfaction.

RESULTS

The majority of patients (65.3%) had clinical insomnia according to the insomnia severity index (ISI). Insomnia correlated significantly but weakly with pain, depression, anxiety and coping; the strongest multivariate correlations were found with depression and anxiety followed by pain interference and pain severity. Pain intensity, depression and anxiety correlated stronger than ISI with respect to the two investigated aspects of health.

CONCLUSIONS

The prevalence of insomnia is high in patients with chronic pain conditions, but the level of importance in relation to other symptoms for health aspects is low, and the associations with other important symptoms are relatively weak. One way to increase the effects of multimodal rehabilitation programs may be to provide interventions directed specifically at insomnia rather than focusing only on interventions that address pain, depression and anxiety. Implications for Rehabilitation The prevalence of insomnia is high in patients with complex chronic pain conditions. Relatively low correlations existed between insomnia and pain intensity, depression, anxiety and other psychological aspects. Pain intensity, anxiety and depression were more important for perceived health aspects than insomnia. One way to increase the effects of multimodal rehabilitation programs may be to also include interventions directed directly to insomnia.

The association of sleep and pain: an update and a path forward

Ample evidence suggests that sleep and pain are related. However, many questions remain about the direction of causality in their association, as well as mechanisms that may account for their association. The prevailing view has generally been that they are reciprocally related. The present review critically examines the recent prospective and experimental literature (2005-present) in an attempt to update the field on emergent themes pertaining to the directionality and mechanisms of the association of sleep and pain. A key trend emerging from population-based longitudinal studies is that sleep impairments reliably predict new incidents and exacerbations of chronic pain. Microlongitudinal studies employing deep subjective and objective assessments of pain and sleep support the notion that sleep impairments are a stronger, more reliable predictor of pain than pain is of sleep impairments. Recent experimental studies suggest that sleep disturbance may impair key processes that contribute to the development and maintenance of chronic pain, including endogenous pain inhibition and joint pain. Several biopsychosocial targets for future mechanistic research on sleep and pain are discussed, including dopamine and opioid systems, positive and negative affect, and sociodemographic factors.

PERSPECTIVE

This critical review examines the recent prospective and experimental research (2005-present) on the association of sleep and pain in an attempt to identify trends suggestive of directionality and potential mechanisms. An update on this literature is needed to guide future clinical efforts to develop and augment treatments for chronic sleep disturbance and chronic pain.

Sleep problems, exercise and obesity and risk of chronic musculoskeletal pain: the Norwegian HUNT study

BACKGROUND

The objective was to investigate the association between self-reported sleep problems and risk of chronic pain in the low back and neck/shoulders, and whether physical exercise and body mass index (BMI) alter this association.

METHODS

The study comprised data on 26 896 women and men in the Nord-Trøndelag Health Study (Norway) without chronic pain or physical impairment at baseline in 1984-86. Occurrence of chronic pain was assessed at follow-up in 1995-97. A generalized linear model was used to calculate adjusted risk ratios.

RESULTS

Sleep problems were dose-dependently associated with risk of pain in the low back and neck/shoulders in both women and men (P < 0.001 both genders). Women and men who reported sleep problems 'sometimes' and 'often/always' had a higher risk of chronic pain of 23-32% and 51-66%, respectively, than those who reported sleep problems 'never'. Combined analyses showed that persons with sleep problems 'sometimes' and who exercised ≥1 hour per week had lower risk of chronic pain in the low back (P < 0.04) and neck/shoulders (P < 0.001) than inactive persons with a similar level of sleep problems (P < 0.04). Likewise, persons with BMI <25 kg/cm(2) and sleep problems 'sometimes' had lower risk of chronic pain in the low back (P < 0.001) and neck/shoulders (P < 0.001) than persons with BMI ≥25 kg/cm(2) and a similar level of sleep problems.

CONCLUSION

Sleep problems are associated with an increased risk of chronic pain in the low back and neck/shoulders. Regular exercise and maintenance of normal body weight may reduce the adverse effect of mild sleep problems on risk of chronic pain.

Cognitive behavioural therapies for fibromyalgia

BACKGROUND

Fibromyalgia (FM) is a clinically well-defined chronic condition of unknown aetiology characterized by chronic widespread pain that often co-exists with sleep disturbances, cognitive dysfunction and fatigue. Patients often report high disability levels and negative mood. Psychotherapies focus on reducing key symptoms, improving daily functioning, mood and sense of personal control over pain.

OBJECTIVES

To assess the benefits and harms of cognitive behavioural therapies (CBTs) for treating FM at end of treatment and at long-term (at least six months) follow-up.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 8), MEDLINE (1966 to 28 August 2013), PsycINFO (1966 to 28 August 2013) and SCOPUS (1980 to 28 August 2013). We searched http://www.clinicaltrials.gov (web site of the US National Institutes of Health) and the World Health Organization Clinical Trials Registry Platform (ICTRP) (http://www.who.int/ictrp/en/) for ongoing trials (last search 28 August,2013), and the reference lists of reviewed articles.

SELECTION CRITERIA

We selected randomised controlled trials of CBTs with children, adolescents and adults diagnosed with FM.

DATA COLLECTION AND ANALYSIS

The data of all included studies were extracted and the risks of bias of the studies were assessed independently by two review authors. Discrepancies were resolved by discussion.

MAIN RESULTS

Twenty-three studies with 24 study arms with CBTs were included. A total of 2031 patients were included; 1073 patients in CBT groups and 958 patients in control groups. Only two studies were without any risk of bias. The GRADE quality of evidence of the studies was low. CBTs were superior to controls in reducing pain at end of treatment by 0.5 points on a scale of 0 to 10 (standardised mean difference (SMD) - 0.29; 95% confidence interval (CI) -0.49 to -0.17) and by 0.6 points at long-term follow-up (median 6 months) (SMD -0.40; 95% CI -0.62 to -0.17); in reducing negative mood at end of treatment by 0.7 points on a scale of 0 to 10 (SMD - 0.33; 95% CI -0.49 to -0.17) and by 1.3 points at long-term follow-up (median 6 months) (SMD -0.43; 95% CI -0.75 to -0.11); and in reducing disability at end of treatment by 0.7 points on a scale of 0 to 10 (SMD - 0.30; 95% CI -0.51 to -0.08) and at long-term follow-up (median 6 months) by 1.2 points (SMD -0.52; 95% CI -0.86 to -0.18). There was no statistically significant difference in dropout rates for any reasons between CBTs and controls (risk ratio (RR) 0.94; 95% CI 0.65 to 1.35).

AUTHORS' CONCLUSIONS

CBTs provided a small incremental benefit over control interventions in reducing pain, negative mood and disability at the end of treatment and at long-term follow-up. The dropout rates due to any reason did not differ between CBTs and controls.

Incidence and predictors of secondary fibromyalgia in an early arthritis cohort

OBJECTIVES

Secondary fibromyalgia (FM) is common among patients with inflammatory arthritis, but little is known about its incidence and the factors leading to its development. The authors examined the incidence of secondary FM in an early inflammatory arthritis cohort, and assessed the association between pain, inflammation, psychosocial variables and the clinical diagnosis of FM.

METHODS

Data from 1487 patients in the Canadian Early Arthritis Cohort, a prospective, observational Canadian cohort of early inflammatory arthritis patients were analysed. Diagnoses of FM were determined by rheumatologists. Incidence rates were calculated, and Cox regression models were used to determine HRs for FM risk.

RESULTS

The cumulative incidence rate was 6.77 (95% CI 5.19 to 8.64) per 100 person-years during the first 12 months after inflammatory arthritis diagnosis, and decreased to 3.58 (95% CI 1.86 to 6.17) per 100 person-years 12-24 months after arthritis diagnosis. Pain severity (HR 2.01, 95% CI 1.17 to 3.46) and poor mental health (HR 1.99, 95% CI 1.09 to 3.62) predicted FM risk. Citrullinated peptide positivity (HR 0.48, 95% CI 0.26 to 0.88) was associated with decreased FM risk. Serum inflammatory markers and swollen joint count were not significantly associated with FM risk.

CONCLUSIONS

The incidence of FM was from 3.58 to 6.77 cases per 100 person-years, and was highest during the first 12 months after diagnosis of inflammatory arthritis. Although inflammation was not associated with the clinical diagnosis of FM, pain severity and poor mental health were associated with the clinical diagnosis of FM. Seropositivity was inversely associated with the clinical diagnosis of FM.

Contextual and time dependent pain in fibromyalgia: an explorative study

Background

Little is known about contextual effects on chronic pain, and how vulnerability factors influence pain in different contexts. We wanted to examine if fibromyalgia (FM) pain varied between two social contexts, i.e. at home versus in a doctor office, when it was measured the same day, and if pain was stable for 14 years when measured in similar contexts (doctor office). Our secondary aim was to explore if pain vulnerability factors varied in the two different contexts.

Findings

Fifty-five female FM patients were included in the study and scored pain in both contexts at baseline. Their age ranged between 21–68 years (mean 45.7), mean education level was 11 years and mean FM-duration was 15.6 years. Their mean pain was perceived significantly lower at home than in a doctor context the same day. However, pain was much more stable when measured in two similar contexts 14 year apart where 30 subjects (54.5%) completed. Predictor analyses revealed that pain vulnerability factors apparently varied by home and doctor contexts.

Conclusion

Pain and pain predictors seem to vary by contexts and time, with less pain at home than to a doctor the same day, but with unchanged pain in the same context after 14 years. Thus, contextual pain cues should be accounted for when pain is measured and treated, e.g. by focusing more on home-measured pain and by optimizing the doctor office context. This explorative study should be followed up by a larger full-scale study.

Are sleep problems and non-specific health complaints risk factors for chronic pain? A prospective population-based study with 17 year follow-up

Introduction

Chronic musculoskeletal pain represents a significant health problem among adults in Norway. The prevalence of chronic pain can be up to 50% in both genders. However, the prevalence of chronic widespread pain is significantly higher in females than in males. Chronic widespread pain is seen as the end of a continuum of pain. There is rather sparse knowledge about the incidence of pain in initially pain free individuals and the course of self-reported pain over time. Moreover, little is known about risk factors for incidence of chronic pain or prognostic factors for the course of self-reported pain. We believe that such knowledge may contribute to develop strategies for treatment at an early stadium of the pain condition and thereby reduce the prevalence of chronic pain included chronic widespread pain.

Aims of the study

The aims of this study were threefold: (1) to calculate the incidence of self-reported musculoskeletal pain in a female cohort, (2) to describe the course of pain and (3) to investigate whether or not health complaints and sleep problems are predictive factors for onset of pain or prognostic factors for the course of pain.

Methods

This is a prospective population-based study of all women between 20 and 50 years who were registered in Arendal, Norway, in 1989 (N = 2498 individuals). A questionnaire about chronic pain (pain >3 months duration in muscles, joints, back or the whole body), modulating factors for pain, sleep problems and seven non-specific health complaints was mailed to all traceable women, in 1990 (N =2498), 1995 (n = 2435) and 2007 (n = 2261). Of these, 1338 responded on all three occasions. Outcome measures were presence and extent of chronic pain.

Results

The prevalence of chronic pain was 57% in 1990 and 61% in 2007. From 1990 to 2007, 53% of the subjects changed pain category. The incidence of chronic pain in initially pain free individuals during follow-up was 44%, whereas the recovery rate was 25%. Impaired sleep quality predicted onset of chronic pain. There was a linear association between the number of health complaints and the incidence of chronic pain in initially pain free individuals. Equivalent results were found for persistence of pain and worsening of pain.

Conclusion

The prevalence of chronic pain was rather stable throughout the follow-up period, but the prevalence of chronic widespread pain increased. Individual changes in pain extent occurred frequently. The presence of sleep disturbances and number of health complaints predicted onset, persistence and worsening of pain.

Implications

Sleep problems must be thoroughly addressed as a possible risk factor for onset or worsening of pain. Elimination of sleep problems in an early phase is an interesting approach in treating chronic pain. More research is needed to illuminate the possible pathogenetic relations between pain, non-specific health complaints, sleep problems and also depression.

Hybrid cognitive-behaviour therapy for individuals with insomnia and chronic pain: a pilot randomised controlled trial

OBJECTIVE

Insomnia is a debilitating comorbidity of chronic pain. This pilot trial tested the utility of a hybrid treatment that simultaneously targets insomnia and pain-related interference.

METHODS

Chronic pain patients with clinical insomnia were randomly allocated to receive 4 weekly 2-h sessions of hybrid treatment (Hybrid Group; n = 10) or to keep a pain and sleep diary for 4 weeks, before receiving the hybrid treatment (Monitoring Group; n = 10). Participants were assessed at the beginning and end of this 4-week period. Primary outcomes were insomnia severity and pain interference. Secondary outcomes were fatigue, anxiety, depression and pain intensity. Ancillary information about the hybrid treatment's effect on psychological processes and sleep (as measured with sleep diary and actigraphy) are also presented, alongside data demonstrating the treatment's clinical significance, acceptability and durability after one and six months. Data from all participants (n = 20) were combined for this purpose.

RESULTS

Compared to symptom monitoring, the hybrid intervention was associated with greater improvement in sleep (as measured with the Insomnia Severity Index and sleep diary) at post-treatment. Although pain intensity did not change, the Hybrid Group reported greater reductions in pain interference, fatigue and depression than the Monitoring Group. Overall, changes associated with the hybrid intervention were clinically significant and durable at 1- and 6-month follow-ups. Participants also rated highly on treatment acceptability.

CONCLUSION

The hybrid intervention appeared to be an effective treatment for chronic pain patients with insomnia. It may be a treatment approach more suited to tackle challenges presented in clinical practice, where problems seldom occur in isolation.

Concordance of sleep and pain outcomes of diverse interventions: an umbrella review

BACKGROUND/OBJECTIVE

Pain influences sleep and vice versa. We performed an umbrella review of meta-analyses on treatments for diverse conditions in order to examine whether diverse medical treatments for different conditions have similar or divergent effects on pain and sleep.

METHODS

We searched published systematic reviews with meta-analyses in the Cochrane Database of Systematic Reviews until October 20, 2011. We identified randomized trials (or meta-analyses thereof, when >1 trial was available) where both pain and sleep outcomes were examined. Pain outcomes were categorized as headache, musculoskeletal, abdominal, pelvic, generic or other pain. Sleep outcomes included insomnia, sleep disruption, and sleep disturbance. We estimated odds ratios for all outcomes and evaluated the concordance in the direction of effects between sleep and various types of pain and the correlation of treatment effects between sleep and pain outcomes.

RESULTS

151 comparisons with 385 different trials met our eligibility criteria. 96 comparisons had concordant direction of effects between each pain outcome and sleep, while in 55 the effect estimates were in opposite directions (P<0.0001). In the 20 comparisons with largest amount of evidence, the experimental drug always had worse sleep outcomes and tended to have worse pain outcomes in 17/20 cases. For headache and musculoskeletal pain, 69 comparisons showed concordant direction of effects with sleep outcomes and 36 showed discordant direction (P<0.0001). For the other 4 pain types there were overall 27 vs. 19 pairs with concordant vs. discordant direction of effects (P = 0.095). There was a weak correlation of the treatment effect sizes for sleep vs. headache/musculoskeletal pain (r = 0.17, P = 0.092).

CONCLUSIONS

Medical interventions tend to have effects in the same direction for pain and sleep outcomes, but exceptions occur. Concordance is primarily seen for sleep and headache or musculoskeletal pain where many drugs may both disturb sleep and cause pain.