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.

Repeating patterns of sleep restriction and recovery: Do we get used to it?

Despite its prevalence in modern society, little is known about the long-term impact of restricting sleep during the week and 'catching up' on weekends. This common sleep pattern was experimentally modeled with three weeks of 5 nights of sleep restricted to 4h followed by two nights of 8-h recovery sleep. In an intra-individual design, 14 healthy adults completed both the sleep restriction and an 8-h control condition, and the subjective impact and the effects on physiological markers of stress (cortisol, the inflammatory marker IL-6, glucocorticoid receptor sensitivity) were assessed. Sleep restriction was not perceived to be subjectively stressful and some degree of resilience or resistance to the effects of sleep restriction was observed in subjective domains. In contrast, physiological stress response systems remain activated with repeated exposures to sleep restriction and limited recovery opportunity. Morning IL-6 expression in monocytes was significantly increased during week 2 and 3 of sleep restriction, and remained increased after recovery sleep in week 2 (p<0.05) and week 3 (p<0.09). Serum cortisol showed a significantly dysregulated 24h-rhythm during weeks 1, 2, and 3 of sleep restriction, with elevated morning cortisol, and decreased cortisol in the second half of the night. Glucocorticoid sensitivity of monocytes was increased, rather than decreased, during the sleep restriction and sleep recovery portion of each week. These results suggest a disrupted interplay between the hypothalamic-pituitary-adrenal and inflammatory systems in the context of repeated exposure to sleep restriction and recovery. The observed dissociation between subjective and physiological responses may help explain why many individuals continue with the behavior pattern of restricting and recovering sleep over long time periods, despite a cumulative deleterious physiological effect.

Sleep characteristics as predictor variables of stress systems markers in insomnia disorder.

This study investigates the extent to which sleep characteristics serve as predictor variables for inflammatory, hypothalamic-pituitary-adrenal and autonomic systems markers. Twenty-nine participants with a diagnosis of insomnia disorder based on the Diagnostic Statistical Manual of Mental Disorders, Fifth Edition (age 25.3 ± 1.6 years, insomnia duration 6.6 ± 0.8 years) and 19 healthy control sleepers (age 25.4 ± 1.4 years) underwent a 2-week at-home evaluation keeping a sleep diary and wearing an actigraph, followed by a visit to the Research Center to measure blood pressure, and collect blood and urine samples. The actigraphy- and diary-based variables of sleep duration, sleep-onset latency, wake after sleep onset and sleep fragmentation/number of night-time awakenings were averaged and entered as dependent variables in regression analyses. Composite scores were calculated for the autonomic (blood pressure, norepinephrine), inflammatory (monocyte counts, interleukin-6, C-reactive protein) and hypothalamic-pituitary-adrenal systems (cortisol), and used as predictor variables in regression models. Compared with controls, individuals with insomnia had a shorter sleep duration (P < 0.05), and a higher hypothalamic-pituitary-adrenal and inflammatory composite score (P < 0.05). The higher inflammatory score was mainly due to higher circulating monocytes (P < 0.05), rather than differences in interleukin-6 or C-reactive protein. In persistent insomnia disorder, cortisol is upregulated and associated with actigraphy- and diary-based wake after sleep onset, suggesting that wake after sleep onset may serve as a marker to identify individuals at increased risks for disorders associated with a hyperactive hypothalamic-pituitary-adrenal system. The absence of autonomic and pro-inflammatory changes (interleukin-6, C-reactive protein), despite a substantial decrease in actigraphic sleep duration, may relate to a higher resilience to the adverse biological consequences of insomnia in this young age group.

Validation of the Individualized Numeric Rating Scale (INRS): a pain assessment tool for nonverbal children with intellectual disability.

Clinical observations suggest that nonverbal children with severe intellectual disability exhibit pain in a wide variety yet uniquely individual ways. Here, we investigate the feasibility and describe the initial psychometrics properties of the Individualized Numeric Rating Scale (INRS), a personalized pain assessment tool for nonverbal children with intellectual disability based on the parent's knowledge of the child. Parents of 50 nonverbal children with severe intellectual disability scheduled for surgery were able to complete the task of describing then rank ordering their child's usual and pain indicators. The parent, bedside nurse and research assistant (RA) triad then simultaneously yet independently scored the patient's post-operative pain using the INRS for a maximum of two sets of pre/post paired observations. A total of 170 triad assessments were completed before (n=85) and after (n=85) an intervention to manage the child's pain. INRS inter-rater agreement between the parents and research nurse was high (ICC 0.82-0.87) across all ratings. Parent and bedside nurse agreement (ICC 0.65-0.74) and bedside nurse and research nurse agreement (ICC 0.74-0.80) also suggest good reliability. A moderate to strong correlation (0.63-0.73) between INRS ratings and NCCPC-PV total scores provides evidence of convergent validity. These results provide preliminary data that the INRS is a valid and reliable tool for assessing pain in nonverbal children with severe intellectual disability in an acute care setting.

Psychological, behavioral, and family characteristics of pediatric patients with chronic pain: a 1-year retrospective study and cluster analysis.

OBJECTIVES: There has been a longstanding recognition that adult patients with chronic pain are not a homogenous population and that there are subgroups of patients who report high levels of distress and interpersonal difficulties as well as subgroups of patients who report little distress and high functioning. The purpose of the present study was to attempt to identify similar subgroups in a pediatric chronic pain population. METHODS: The sample consisted of 117 children with chronic pain and their parents who were assessed in a multidisciplinary pain clinic during 2001. Participants completed a set of psychologic self-report questionnaires, as well as demographic and pain characteristic information. A cluster analysis was conducted to identify 3 distinct subgroups of patients to replicate similar studies of adult chronic pain sufferers. RESULTS: Overall, mean scores were within population norms on measures of distress and family functioning, with somatic symptoms at a level of clinical significance. The cluster analysis identified the 3 subgroups that were strikingly similar to those identified in adult chronic pain populations: one with high levels of distress and disability, another with relatively low scores on distress and disability, and a third group that scored in between the other 2 on these measures but with marked low family cohesion. DISCUSSION: The similarity of these subgroups to the adult chronic pain population subgroups as well as implications for future studies are discussed.

Physical therapy and cognitive-behavioral treatment for complex regional pain syndromes.

Complex regional pain syndromes (CRPS; type 1, reflex sympathetic dystrophy, and type 2, causalgia) involve persistent pain, allodynia, and vasomotor signs. We conducted a prospective, randomized, single-blind trial of physical therapy (PT) and cognitive-behavioral treatment for children and adolescents with CRPS. Children 8 to 17 years of age (n = 28) were randomly assigned to either group A (PT once per week for 6 weeks) or group B (PT 3 times per week for 6 weeks). Both groups received 6 sessions of cognitive-behavioral treatment. Assessments of pain and function were repeated at two follow-up time periods. Outcomes were compared at the three time points through the use of parametric or nonparametric analysis of variance and post hoc tests. All five measures of pain and function improved significantly in both groups after treatment, with sustained benefit evident in the majority of patients at long-term follow-up. Recurrent episodes were reported in 50% of patients, and 10 patients eventually received sympathetic blockade. Most children with CRPS showed reduced pain and improved function with a noninvasive rehabilitative treatment approach. Long-term functional outcomes were also very good.