Pain
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The comprehensive assessment of pain-related human phenotypes requires combinations of nociceptive measures that produce complex high-dimensional data, posing challenges to bioinformatic analysis. In this study, we assessed established experimental models of heat hyperalgesia of the skin, consisting of local ultraviolet-B (UV-B) irradiation or capsaicin application, in 82 healthy subjects using a variety of noxious stimuli. We extended the original heat stimulation by applying cold and mechanical stimuli and assessing the hypersensitization effects with a clinically established quantitative sensory testing (QST) battery (German Research Network on Neuropathic Pain). ⋯ Unsupervised machine-learning techniques, implemented as emergent self-organizing maps, hinted at subgroups responding to topical application of capsaicin. The distinction among subgroups was based on sensitivity to pressure pain, which could be attributed to sex differences, with women being more sensitive than men. Thus, while UV-B and capsaicin share a major component of heat pain sensitization, they differ in their effects on QST parameter patterns in healthy subjects, suggesting a lack of redundancy between these models.
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Individuals with chronic pain may experience negative responses from spouse, family, and friends. Responses such as overt criticism and hostility may be associated with worsening pain and function for chronic pain sufferers. We used a laboratory procedure to evaluate whether variability in spouse criticism/hostility exhibited toward chronic low back pain (CLBP) patients during a conflictual discussion predicted variability in patient pain and function during a subsequent pain-induction task. ⋯ Results support the hypothesis that spouse criticism and hostility-actually expressed or perceived-may worsen CLBP patient symptoms. Further, women patients and patients high in depressive symptoms appeared most vulnerable to spouse criticism/hostility. Thus, negative marital communication patterns may be appropriate targets for intervention, especially among these 2 at risk groups.
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Recent evidence-based guidelines for long-term opioid therapy (LTOT) for chronic noncancer pain (CNCP) have defined daily morphine equivalent doses (MEQ/d) that require particular caution. The recommendation for a threshold MEQ/d is based on North American studies that have demonstrated negative health outcomes associated with high-dose LTOT for CNCP. We have conducted a retrospective cross-sectional study using an anonymized German health claims database, including 4,028,618 persons insured by 69 German statutory health insurances, representative of age and sex for the German population in 2014. ⋯ Those receiving German guideline-recommended opioid treatments vs those receiving high-dose LTOT differed for the following parameters: risky opioid prescribing (combination with tranquilizers) (11.1% vs 14.3%; P < 0.001), hospital admissions because of mental and behavioral disorders due to alcohol, opioids, tranquilizers, multiple substances and intoxication by narcotic agents (1.6% vs 2.9%; P < 0.001), and total health costs (7259 vs 10,732 Euro; P < 0.001). The difference in annual costs between the 2 groups was largely due to differences in pharmaceutical costs in the outpatient setting (2282 vs 5402 &OV0556;; P < 0.001). These data confirm recommendations for a threshold MEQ/d for CNCP as recommended by recent opioid prescribing guidelines for CNCP.
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Higher levels of fear have been shown to partly explain individual differences in placebo analgesic responding. The catechol-O-methyltransferase (COMT) rs4680 Val158Met polymorphism has been associated with both increased placebo analgesia and increased fear-related behavior, in what appears to be inconsistent findings in the literature. The aim of the study was therefore to investigate placebo analgesia and fear-related processes with regard to the COMT genotype, to sort out whether the Met-allele is associated with increased placebo analgesia or increased fear of pain (FOP). ⋯ There was a main effect of the COMT genotype on fear of medical pain (P = 0.032), and Met-allele carriers reported significantly higher fear of medical pain compared with the Val-allele (P = 0.044). We observed no effect of the COMT genotype on mean pain-level report or placebo analgesia. Thus, we conclude that the Met-allele seems to be associated with the negative emotional process of fear, but not with placebo analgesia.