The journal of pain : official journal of the American Pain Society
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Genetic factors play a role in the etiology of persistent pain conditions, putatively by modulating underlying processes such as nociceptive sensitivity, psychological well-being, inflammation, and autonomic response. However, to date, only a few genes have been associated with temporomandibular disorders (TMD). This study evaluated 358 genes involved in pain processes, comparing allelic frequencies between 166 cases with chronic TMD and 1,442 controls enrolled in the OPPERA (Orofacial Pain: Prospective Evaluation and Risk Assessment) study cooperative agreement. To enhance statistical power, 182 TMD cases and 170 controls from a similar study were included in the analysis. Genotyping was performed using the Pain Research Panel, an Affymetrix gene chip representing 3,295 single nucleotide polymorphisms, including ancestry-informative markers that were used to adjust for population stratification. Adjusted associations between genetic markers and TMD case status were evaluated using logistic regression. The OPPERA findings provided evidence supporting previously reported associations between TMD and 2 genes: HTR2A and COMT. Other genes were revealed as potential new genetic risk factors for TMD, including NR3C1, CAMK4, CHRM2, IFRD1, and GRK5. While these findings need to be replicated in independent cohorts, the genes potentially represent important markers of risk for TMD, and they identify potential targets for therapeutic intervention. ⋯ Genetic risk factors for TMD pain were explored in the case-control component of the OPPERA cooperative agreement, a large population-based prospective cohort study. Over 350 candidate pain genes were assessed using a candidate gene panel, with several genes displaying preliminary evidence for association with TMD status.
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Many studies report that people with temporomandibular disorders (TMD) are more sensitive to experimental pain stimuli than TMD-free controls. Such differences in sensitivity are observed in remote body sites as well as in the orofacial region, suggesting a generalized upregulation of nociceptive processing in TMD cases. This large case-control study of 185 adults with TMD and 1,633 TMD-free controls measured sensitivity to painful pressure, mechanical cutaneous, and heat stimuli, using multiple testing protocols. Based on an unprecedented 36 experimental pain measures, 28 showed statistically significantly greater pain sensitivity in TMD cases than controls. The largest effects were seen for pressure pain thresholds at multiple body sites and cutaneous mechanical pain threshold. The other mechanical cutaneous pain measures and many of the heat pain measures showed significant differences, but with lesser effect sizes. Principal component analysis (PCA) of the pain measures derived from 1,633 controls identified 5 components labeled: 1) heat pain ratings; 2) heat pain aftersensations and tolerance; 3) mechanical cutaneous pain sensitivity; 4) pressure pain thresholds; and 5) heat pain temporal summation. These results demonstrate that compared to TMD-free controls, chronic TMD cases are more sensitive to many experimental noxious stimuli at extracranial body sites, and provide for the first time the ability to directly compare the case-control effect sizes of a wide range of pain sensitivity measures. ⋯ This article describes experimental pain sensitivity differences between a large sample of people with chronic TMD and non-TMD controls, using multiple stimulus modalities and measures. Variability in the magnitude and consistency of case-control differences highlight the need to consider multiple testing measures to adequately assess pain processing alterations in chronic pain conditions.
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There is growing interest in the role that positive aspects of psychological adjustment, such as pain acceptance, hope, and optimism, may play in explaining adjustment in persons suffering from persistent pain. This study conducted in obese patients with persistent musculoskeletal pain (N = 89) examined the degree to which pain acceptance and hope explained pain intensity, pain unpleasantness, psychological distress, and pain-related disability, after controlling for the effects of optimism. In correlational analyses, pain acceptance and optimism were associated with psychological distress and pain disability with hope being related to only psychological distress. Pain acceptance, optimism, and hope were not significantly associated with pain. Hierarchical linear regression (HLR) analyses found that pain acceptance remained a significant predictor of psychological distress and pain disability after controlling for optimism, demographic, and medical variables. HLR analyses found that hope was not a significant predictor of psychological distress after controlling for optimism, pain acceptance, and demographic and medical variables. The results of this study are important because they indicate that pain acceptance, hope, and optimism are all related to pain adjustment. They also highlight the importance of controlling for optimism when examining the effects of pain acceptance and hope on pain adjustment. ⋯ In a sample of obese patients with persistent musculoskeletal pain, pain acceptance was a significant predictor of psychological distress and pain disability even after controlling for optimism, demographic, and medical variables. These results add to the growing literature on the importance of pain acceptance in understanding adjustment to persistent pain.