Pain
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Heritability of Pain Catastrophizing and Associations with Experimental Pain Outcomes: A Twin Study.
This study used a twin paradigm to examine genetic and environmental contributions to pain catastrophizing and the observed association between pain catastrophizing and cold-pressor task (CPT) outcomes. Male and female monozygotic (n = 206) and dizygotic twins (n = 194) from the University of Washington Twin Registry completed a measure of pain catastrophizing and performed a CPT challenge. ⋯ Additionally, the observed associations between pain catastrophizing and CPT outcomes were not found attributable to shared genetics or environmental exposure, which suggests a direct relationship between catastrophizing and experimental pain outcomes. This study is the first to examine the heritability of pain catastrophizing and potential processes by which pain catastrophizing is related to experimental pain response.
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Human experimental pain models are widely used to study drug effects under controlled conditions, but they require further optimization to better reflect clinical pain conditions. To this end, we measured experimentally induced pain in 110 (46 men) healthy volunteers. The quantitative sensory testing (QST) battery (German Research Network on Neuropathic Pain) was applied on untreated ("control") and topical capsaicin-hypersensitized ("test") skin. ⋯ Inclusion in the respective clusters was predictable at a cross-validated accuracy of 86.9% by a classification and regression tree comprising 3 QST parameters (mechanical pain sensitivity, wind-up ratio, and z-transformed thermal sensory limen) from the control sites. Thus, we found that topical capsaicin partly induced the desired clinical pattern of neuropathic pain in a preselectable subgroup of healthy subjects to a degree that fuels expectations that experimental pain models can be optimized toward mimicking clinical pain. The subjects, therefore, qualify for enrollment in analgesic drug studies that use highly selected cohorts to enhance predictivity for clinical analgesia.
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Fibromyalgia (FM) is a chronic pain condition often resulting in functional impairments. Nonrestorative sleep is a prominent symptom of FM that is related to disability, but the day-to-day mechanisms relating the prior night's sleep quality to next-day reports of disability have not been examined. This study examined the within-day relations among early-morning reports of sleep quality last night, late-morning reports of pain and positive and negative affect, and end-of-day reports of activity interference. ⋯ Of note, positive affect was a stronger mediator than pain and negative affect was not a significant mediator. In summary, the findings identify 2 parallel mechanisms, pain and positive affect, through which the prior night's sleep quality predicts disability the next day in patients with FM. Furthermore, results highlight the potential utility of boosting positive affect after a poor night's sleep as one means of preserving daily function in FM.
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Chronic pain is associated with large societal costs, but few studies have investigated the total costs of chronic pain with respect to elderly subjects. The elderly usually require informal care, care performed by municipalities, and care for chronic diseases, all factors that can result in extensive financial burdens on elderly patients, their families, and the social services provided by the state. This study aims to quantify the societal cost of chronic pain in people of age 65 years and older and to assess the impact of chronic pain on quality of life. ⋯ Consumed resources increased with the severity of chronic pain. Clear differences in EQ-5D were found with respect to the severity of pain. This study found an association between resource use and severity of chronic pain in elderly subjects: the more severe the chronic pain, the more extensive (and expensive) the use of resources.
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The relevance of a phobia-based conceptualization of fear for individuals with chronic pain has been much debated in the literature. This study investigated whether patients with highly fearful chronic low back pain show distinct physiological reaction patterns compared with less fearful patients when anticipating aversive back pain-related movements. We used an idiosyncratic fear induction paradigm and collected 2 different measures of autonomic nervous system activation and muscle tension in the lower back. ⋯ According to Bradley and Lang defense cascade model, this response is typical of a fear reaction. Participants showing the psychophysiological pattern typical of fear also had elevated scores on some self-report measures of components of the fear-avoidance model, relative to participants showing the reaction pattern characteristic of attention. This study is the first to provide psychophysiological evidence for the fear-avoidance model of chronic pain.