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Twin studies provide a method for estimating the heritability of phenotypes and for examining genetic and environmental relationships between phenotypes. We conducted a systematic review of twin studies of pain, including both clinical and experimental pain phenotypes. Fifty-six papers were included, whereof 52 addressed clinical phenotypes. Of the most comprehensively studied phenotypes, available data indicates heritability around 50% for migraine, tension-type headache and chronic widespread pain, around 35% for back and neck pain, and around 25% for irritable bowel syndrome. However, differences in phenotype definitions make these results somewhat uncertain. All clinical studies relied on dichotomous outcomes and none used pain intensity as continuous phenotype. This is a major weakness of the reviewed studies and gives reason to question their validity with respect to pain mechanisms. Experimental pain studies indicate large differences in heritability across pain modalities. Whereas there is evidence for substantial common genetic risk across many clinical pain conditions, different experimental pain phenotypes appear to be associated with different genetic factors. Recommendations for future research include inclusion of pain intensity scaling and number of pain sites in phenotyping. Furthermore, studies examining the genetic relationships between pain phenotypes, in particular between clinical and experimental phenotypes, should be prioritized. [ABSTRACT FROM AUTHOR]

Please cite this paper as: Bjelland E, Eberhard-Gran M, Nielsen C, Eskild A. Age at menarche and pelvic girdle syndrome in pregnancy: a population study of 74 973 women. BJOG 2011;118:1646-1652. Objective To study the association of age at menarche with presence of pelvic girdle syndrome in pregnancy. Design Population study. Setting Norway 1999-2007. Population A total of 74 973 pregnant women in the Norwegian Mother and Child Cohort Study. Methods Data were obtained by self-administered questionnaires in weeks 17 and 30 of gestation. Main outcome measure Pelvic girdle syndrome in pregnancy at 30 weeks of gestation, defined as pain in the pubic symphysis in the anterior pelvis and in both sacroiliac joints in the posterior pelvis. Results The prevalence of pelvic girdle syndrome was 20.6% (328/1593) in women with menarche before the age of 11, it was 16.3% (3200/22 044) in women with menarche at the age of 12 and 12.7% (1252/9859) in women with menarche after the age of 14 (chi-square test for trend, P < 0.001). The inverse association of age at menarche with pelvic girdle syndrome remained after adjustment for body mass index, maternal age, parity, educational level, previous low back pain, emotional distress and physically demanding work. Women with early menarche and high body mass index had the highest prevalence of pelvic girdle syndrome, but the association of early menarche with pelvic girdle syndrome was similar in women with and without high body mass index. Conclusions Early menarche was associated with increased prevalence of pelvic girdle syndrome in pregnancy. Factors associated with early menarche may play a role in the development of pelvic girdle pain. [ABSTRACT FROM AUTHOR]

Aim: To assess the relationship between periodontitis and experimental pain tolerance., Materials and Methods: Participants from the population-based seventh survey of the Tromsø Study with data on periodontitis were included (n = 3666, 40-84 years old, 51.6% women). Pain tolerance was assessed through (i) pressure pain tolerance (PPT) test with a computerized cuff pressure algometry on the leg, and (ii) cold-pressor tolerance (CPT) test where one hand was placed in circulating 3°C water. Cox proportional hazard regression was used to assess the association between periodontitis and pain tolerance adjusted for age, sex, education, smoking and obesity., Results: In the fully adjusted model using the 2012 Centers for Disease Control/American Academy of Periodntology case definitions for surveillance of periodontitis, moderate (hazard ratio [HR] = 1.09; 95% confidence interval [CI]: 1.01, 1.18) and severe (HR = 1.25, 95% CI: 1.11, 1.42) periodontitis were associated with decreased PPT. Using the 2018 classification of periodontitis, having Stage II/III/IV periodontitis was significantly associated with decreased PPT (HR = 1.09; 95% CI: 1.01, 1.18) compared with having no or stage I periodontitis. There were no significant associations between periodontitis and CPT in fully adjusted models., Conclusions: Moderate and severe periodontitis was associated with experimental PPT., (© 2024 The Authors. Journal of Clinical Periodontology published by John Wiley & Sons Ltd.)

Background: Unrecognized myocardial infarction (MI) is a prevalent condition associated with a similar risk of death as recognized MI. It is unknown why some persons experience MI with few or no symptoms; however, one possible explanation is attenuated pain sensitivity. To our knowledge, no previous study has examined the association between pain sensitivity and recognition of MI., Methods and Results: We conducted a population-based cross-sectional study with 4849 included participants who underwent the cold pressor test (a common experimental pain assay) and ECG. Unrecognized MI was present in 387 (8%) and recognized MI in 227 (4.7%) participants. Participants with unrecognized MI endured the cold pressor test significantly longer than participants with recognized MI (hazard ratio for aborting the cold pressor test, 0.64; CI, 0.47-0.88), adjusted for age and sex. The association was attenuated and borderline significant after multivariable adjustment. The association between unrecognized MI and lower pain sensitivity was stronger in women than in men, and statistically significant in women only, but interaction testing was not statistically significant (P for interaction=0.14)., Conclusions: Our findings suggest that persons who experience unrecognized MI have reduced pain sensitivity compared with persons who experience recognized MI. This may partially explain the lack of symptoms associated with unrecognized MI., (© 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.)

Background: The contribution of nerve lesions and neuropathic pain to persistent post-surgical pain (PPSP) is poorly established. The aim of this study was to assess the association between PPSP and symptoms and signs of possible nerve injury in an unselected surgical sample., Methods: Eighty-one individuals with and without persistent pain after surgical procedures, were recruited from a cross-sectional study. Follow-up examination with questionnaires and quantitative sensory testing was performed 15-32 months later (21-64 months after surgery)., Results: The median rating of maximum pain intensity among individuals with PPSP decreased from numerical rating scale 4/10 at baseline to 2/10 at follow-up, but considerable changes occurred in both directions. Individuals with PPSP at follow-up were significantly more likely to self-report sensory abnormalities than those without PPSP; however, results from sensory testing did not differ significantly between the groups. Self-report of sensory disturbances at the site of surgery was associated with increased warm detection thresholds and tactile pain thresholds. Among individuals with PPSP, 61% had positive findings on sensory testing, suggesting probable neuropathic pain., Conclusion: In this study, associations between self-reported symptoms and PPSP were stronger than associations between self-reported symptoms and results of psychophysical tests. Fluctuations in pain intensity together with wide ranges for normal variability in sensory functions, hampers detection of significant group differences. Methodological aspects of quantitative sensory testing applied in a mixed clinical sample are discussed., (© 2015 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.)

Background: The aim of this prospective study was to investigate the role of labor pain and overall birth experience in the development of posttraumatic stress symptoms in a comprehensive framework., Methods: The study sample (N = 1893) comprised women with a vaginal delivery and was drawn from the Akershus Birth Cohort, which targeted all women scheduled to give birth at Akershus University Hospital in Norway. Questionnaires were given at three different stages: from pregnancy weeks 17 to 32, from the maternity ward, and from 8 weeks postpartum. Data were also obtained from the hospital's birth record. Using structural equation modeling, a prospective mediation model was tested., Results: Posttraumatic stress symptoms were significantly related to both labor pain (r = 0.23) and overall birth experience (r = 0.39). A substantial portion (33%) of the effect of labor pain on posttraumatic stress symptoms was mediated by the overall birth experience., Conclusions: Although the results of this study showed that both labor pain and overall birth experience played a role in the development of posttraumatic stress symptoms after childbirth, overall birth experience appeared to be the central factor. The women's birth experience was not only related to posttraumatic stress symptoms directly but also mediated a substantial portion of the effect of labor pain on posttraumatic stress symptoms. Future work should address which areas of birth experience confer protective effects on women to improve clinical care., (© 2014, Copyright the Authors Journal compilation © 2014, Wiley Periodicals, Inc.)