The journal of pain : official journal of the American Pain Society
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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. ⋯ 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.
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Factors contributing to pain following surgery are poorly understood, with previous research largely focused on adults. With approximately 6 million children undergoing surgery each year, there is a need to study pediatric persistent postsurgical pain. The present study includes patients with adolescent idiopathic scoliosis undergoing spinal fusion surgery enrolled in a prospective, multicentered registry examining postsurgical outcomes. The Scoliosis Research Society Questionnaire-Version 30, which includes pain, activity, mental health, and self-image subscales, was administered to 190 patients prior to surgery and at 1 and 2 years postsurgery. A subset (n = 77) completed 5-year postsurgery data. Pain prevalence at each time point and longitudinal trajectories of pain outcomes derived from SAS PROC TRAJ were examined using analyses of variance and post hoc pairwise analyses across groups. Thirty-five percent of patients reported pain in the moderate to severe range presurgery. One year postoperation, 11% reported pain in this range, whereas 15% reported pain at 2 years postsurgery. At 5 years postsurgery, 15% of patients reported pain in the moderate to severe range. Among the 5 empirically derived pain trajectories, there were significant differences on self-image, mental health, and age. Identifying predictors of poor long-term outcomes in children with postsurgical pain may prevent the development of chronic pain into adulthood. ⋯ This investigation explores the prevalence of pediatric pain following surgery, up to 5 years after spinal fusion surgery. Five pain trajectories were identified and were distinguishable on presurgical characteristics of age, mental health, and self-image. This is the largest study to examine longitudinal pediatric pain trajectories after surgery.
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Several studies have reported reduced cerebral gray matter (GM) volume or density in chronic pain conditions, but there is limited research on the plasticity of the human cortex in response to psychological interventions. We investigated GM changes after cognitive-behavioral therapy (CBT) in patients with chronic pain. We used voxel-based morphometry to compare anatomic magnetic resonance imaging scans of 13 patients with mixed chronic pain types before and after an 11-week CBT treatment and to 13 healthy control participants. CBT led to significant improvements in clinical measures. Patients did not differ from healthy controls in GM anywhere in the brain. After treatment, patients had increased GM in the bilateral dorsolateral prefrontal, posterior parietal, subgenual anterior cingulate/orbitofrontal, and sensorimotor cortices, as well as hippocampus, and reduced GM in supplementary motor area. In most of these areas showing GM increases, GM became significantly higher than in controls. Decreased pain catastrophizing was associated with increased GM in the left dorsolateral prefrontal and ventrolateral prefrontal cortices, right posterior parietal cortex, somatosensory cortex, and pregenual anterior cingulate cortex. Although future studies with additional control groups will be needed to determine the specific roles of CBT on GM and brain function, we propose that increased GM in the prefrontal and posterior parietal cortices reflects greater top-down control over pain and cognitive reappraisal of pain, and that changes in somatosensory cortices reflect alterations in the perception of noxious signals. ⋯ An 11-week CBT intervention for coping with chronic pain resulted in increased GM volume in prefrontal and somatosensory brain regions, as well as increased dorsolateral prefrontal volume associated with reduced pain catastrophizing. These results add to mounting evidence that CBT can be a valuable treatment option for chronic pain.
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Observational Study
Clinical orofacial characteristics associated with risk of first-onset TMD: the OPPERA prospective cohort study.
Case-control studies have documented clinical manifestations of chronic temporomandibular disorder (TMD), whereas clinical predictors of TMD development are largely unknown. We evaluated 41 clinical orofacial characteristics thought to predict first-onset TMD in a prospective cohort study of U.S. adults aged 18 to 44 years. During the median 2.8-year follow-up period, 2,737 people completed quarterly screening questionnaires. Those reporting symptoms were examined and 260 people were identified with first-onset TMD. Univariate and multivariable Cox regression models quantified associations between baseline clinical orofacial measures and TMD incidence. Significant predictors from baseline self-report instruments included oral parafunctions, prior facial pain and its life-impact, temporomandibular joint noises and jaw locking, and nonspecific orofacial symptoms. Significant predictors from the baseline clinical examination were pain on jaw opening and pain from palpation of masticatory, neck, and body muscles. Examiner assessments of temporomandibular joint noise and tooth wear facets did not predict incidence. In multivariable analysis, nonspecific orofacial symptoms, pain from jaw opening, and oral parafunctions predicted TMD incidence. The results indicate that only a few orofacial examination findings influenced TMD incidence, and only to a modest degree. More pronounced influences were found for self-reported symptoms, particularly those that appeared to reflect alterations to systems beyond the masticatory tissues. ⋯ OPPERA's prospective cohort study identifies predictors of first-onset TMD comprising self-reported orofacial symptoms and examination findings. The results suggest a complex pattern of TMD etiology that is influenced by disorders locally, in masticatory tissues, and systemically, in pain-regulatory systems.
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Observational Study
Study protocol, sample characteristics, and loss to follow-up: the OPPERA prospective cohort study.
When studying incidence of pain conditions such as temporomandibular disorder (TMD), repeated monitoring is needed in prospective cohort studies. However, monitoring methods usually have limitations and, over a period of years, some loss to follow-up is inevitable. The OPPERA prospective cohort study of first-onset TMD screened for symptoms using quarterly questionnaires and examined symptomatic participants to definitively ascertain TMD incidence. During the median 2.8-year observation period, 16% of the 3,263 enrollees completed no follow-up questionnaires, others provided incomplete follow-up, and examinations were not conducted for one third of symptomatic episodes. Although screening methods and examinations were found to have excellent reliability and validity, they were not perfect. Loss to follow-up varied according to some putative TMD risk factors, although multiple imputation to correct the problem suggested that bias was minimal. A second method of multiple imputation that evaluated bias associated with omitted and dubious examinations revealed a slight underestimate of incidence and some small biases in hazard ratios used to quantify effects of risk factors. Although "bottom line" statistical conclusions were not affected, multiply-imputed estimates should be considered when evaluating the large number of risk factors under investigation in the OPPERA study. ⋯ These findings support the validity of the OPPERA prospective cohort study for the purpose of investigating the etiology of first-onset TMD, providing the foundation for other papers investigating risk factors hypothesized in the OPPERA project.