Associations between cognitive test scores and pain tolerance: The Tromsø study.

OBJECTIVES: Previous studies have suggested that experimental pain sensitivity is associated with cognitive function. The aim of this study is to assess this relationship in a large population-based sample. METHODS: We included 5,753 participants (aged 40-84 years) from the seventh wave of the population-based Tromsø Study who had been examined with cognitive tests and experimental pain assessments, and for whom information on covariates were available. Cox regression models were fitted using standardized scores on cognitive tests (12-word immediate recall test, digit symbol coding test, and Mini-Mental State Examination [MMS-E]) as the independent variable and cold pressor or cuff pressure pain tolerance as the dependent variables. Statistical adjustment was made for putative confounders, namely, age, sex, education, smoking, exercise, systolic blood pressure, body mass index, symptoms indicating anxiety or depression, analgesic use, and chronic pain. RESULTS: In multivariate analysis, cold pressor tolerance time was significantly associated with test scores on the 12-word immediate recall test (hazard ratio [HR] 0.93, 95% confidence interval [CI] 0.90-0.97, p < 0.001), the digit symbol coding test (HR 0.94, 95% CI 0.89-0.98, p = 0.004), and the MMS-E (HR 0.93, 95% CI 0.90-0.96 p < 0.001). Tolerance to cuff pressure algometry was significantly associated with 12-word immediate recall (HR 0.94-0.97, p < 0.001) and Digit Symbol Coding test scores (HR 0.93, 95% CI 0.89-0.96, p < 0.001) while there was no significant association with Mini Mental State Examination test score (HR 0.98, 95% CI 0.95-1.00, p = 0.082). CONCLUSION: Lower pain tolerance was associated with poorer performance on cognitive tests.

Pain tolerance after stroke: The Tromsø study.

BACKGROUND: Stroke lesions might alter pain processing and modulation by affecting the widely distributed network of brain regions involved. We aimed to compare pain tolerance in stroke survivors and stroke-free persons in the general population, with and without chronic pain. METHODS: We included all participants of the sixth and seventh wave of the population-based Tromsø Study who had been tested with the cold pressor test (hand in cold water bath, 3°C, maximum time 106 s in the sixth wave and 120 s in the seventh) and who had information on previous stroke status and covariates. Data on stroke status were obtained from the Tromsø Study Cardiovascular Disease Register and the Norwegian Stroke Register. Cox regression models were fitted using stroke prior to study attendance as the independent variable, cold pressor endurance time as time variable and hand withdrawal from cold water as event. Statistical adjustments were made for age, sex, diabetes, hypertension, hyperlipidaemia, body mass index and smoking. RESULTS: In total 21,837 participants were included, 311 of them with previous stroke. Stroke was associated with decreased cold pain tolerance time, with 28% increased hazard of hand withdrawal (hazard ratio [HR] 1.28, 95% CI 1.10-1.50). The effect was similar in participants with (HR 1.28, 95% CI 0.99-1.66) and without chronic pain (HR 1.29, 95% CI 1.04-1.59). CONCLUSIONS: Stroke survivors, with and without chronic pain, had lower cold pressor pain tolerance, with possible clinical implications for pain in this group. SIGNIFICANCE: We found lower pain tolerance in participants with previous stroke compared to stroke-free participants of a large, population-based study. The association was present both in those with and without chronic pain. The results may warrant increased awareness by health professionals towards pain experienced by stroke patients in response to injuries, diseases and procedures.

A bidirectional study of the association between insomnia, high-sensitivity C-reactive protein, and comorbid low back pain and lower limb pain.

OBJECTIVES: To examine the possible bidirectional association between insomnia and comorbid chronic low back pain (LBP) and lower limb pain and to explore whether high-sensitivity C-reactive protein (hsCRP) amplifies these associations. METHODS: We calculated adjusted risk ratios (RR) with 95% confidence intervals (CI) for the development of insomnia and mild-to-severe chronic LBP and lower limb pain at 11 years follow-up in participants aged ≥32 years and with hsCRP ≤10 mg/L at baseline in 2007-2008: 3,714 without chronic LBP or lower limb pain (sample 1) and 7,892 without insomnia (sample 2). RESULTS: Compared to participants without chronic pain, participants with comorbid chronic LBP and lower limb pain had a RR of insomnia of 1.37 (95% CI 1.12-1.66). Compared with participants without insomnia, participants with insomnia did not have an increased risk of comorbid chronic LBP and lower limb pain (RR: 1.06, 95% CI 0.76-1.46); however, participants with insomnia had a RR of chronic LBP of 1.20 (95% CI 1.02-1.42). There was no strong amplifying effect of elevated hsCRP (3.00-10.0 mg/L) on these associations. CONCLUSIONS: These findings suggest that elevated hsCRP does not amplify the associations between insomnia and mild-to-severe chronic LBP and lower limb pain. Further research using data on the temporal relation between insomnia, chronic pain, and inflammatory responses are required to fully understand the causal pathways.

Long-term male-specific chronic pain via telomere- and p53­mediated spinal cord cellular senescence.

Mice with experimental nerve damage can display long­lasting neuropathic pain behavior. We show here that 4 months and later after nerve injury, male but not female mice displayed telomere length (TL) reduction and p53­mediated cellular senescence in the spinal cord, resulting in maintenance of pain and associated with decreased lifespan. Nerve injury increased the number of p53­positive spinal cord neurons, astrocytes, and microglia, but only in microglia was the increase male­specific, matching a robust sex specificity of TL reduction in this cell type, which has been previously implicated in male­specific pain processing. Pain hypersensitivity was reversed by repeated intrathecal administration of a p53­specific senolytic peptide, only in male mice and only many months after injury. Analysis of UK Biobank data revealed sex-specific relevance of this pathway in humans, featuring male­specific genetic association of the human p53 locus (TP53) with chronic pain and a male-specific effect of chronic pain on mortality. Our findings demonstrate the existence of a biological mechanism maintaining pain behavior, at least in males, occurring much later than the time span of virtually all extant preclinical studies.

The association between age at menarche and chronic pain outcomes in women: the Tromsø Study, 2007 to 2016.

ABSTRACT: Sex differences in chronic pain are well established with documented predominance in women. This study assessed relationships between age at menarche and chronic pain, site-specific chronic pain, pain characteristics, and chronic widespread pain (CWP). We used data from the Tromsø Study conducted in 2007 to 2008 and 2015 to 2016 (Tromsø 6 and Tromsø 7 waves) including participants aged 30 to 99 years. The associations between age at menarche and chronic pain were examined in Tromsø 6 (n = 6449), Tromsø 7 (n = 5681), and the combination of Tromsø 6 and Tromsø 7 (n = 12,130). Tromsø 7 data were used further to examine the associations between age at menarche and site-specific chronic pain, 4 pain characteristics (pain duration, pain intensity, episode duration, and episode frequency), and CWP. All analyses were adjusted for body mass index, age, and economic status of the household in childhood. Lower age at menarche was associated with an increased risk of chronic pain in all 3 samples (risk ratio for each year delay in menarche 0.98, 95% CI [0.97 to 0.99] across samples). Risk differences were -0.014, CI 95% (-0.02 to -0.005) in Tromsø 6, -0.011, CI 95% (-0.02 to -0.02) in Tromsø 7, and -0.012, CI 95% (-0.02 to -0.01) in the combined sample. Age at menarche was significantly associated with chronic pain in the neck, abdomen, and both arms, and CWP. Of the 4 pain characteristics, pain duration was statistically significant. We conclude that early menarche is an independent risk factor for pain across a broad spectrum of pain outcomes.

Tinnitus and associations with chronic pain: The population-based Tromsø Study (2015-2016).

Tinnitus and pain have many similarities. Both are subjective sensations that may turn chronic, they are often accompanied by hypersensitivity in their respective sensory system, and overlapping brain changes have been observed. Since no population study has examined the empirical association between chronic pain and tinnitus, the present study aimed to explore the relationship in a general adult population. We used data from the seventh survey of the Tromsø Study (2015-2016). Participants (aged ≥40) responded to questions about pain and tinnitus. Using multiple logistic regression, we analysed the adjusted relationship between chronic pain and tinnitus in the full sample (n = 19,039), using several tinnitus definitions ranging from tinnitus >5 minutes within the past 12 months (broadest definition) to at least weekly and highly bothersome tinnitus (strictest definition). We also analysed relationships between number of body regions with pain, pain intensity and bothering, and tinnitus >5 minutes, among participants with chronic pain (n = 11,589). We found an association between chronic pain and tinnitus that was present irrespective of tinnitus definition, but was stronger with more bothersome tinnitus. With chronic pain, the odds of tinnitus >5 minutes was 64% higher, while odds of at least weekly, highly bothersome tinnitus was 144% higher than without chronic pain. Among participants with chronic pain, the number of pain regions was the pain variable most strongly associated with tinnitus >5 minutes (OR = 1.17 (95% CI: 1.14-1.20) for an increase of one region), whereas the other pain variables (intensity and bothering) showed weaker associations. All chronic pain variables had significant interactions with age, with the strongest associations for the youngest individuals (40-54 years). Our findings support the existence of an association between chronic pain and tinnitus and emphasises the importance of examining for comorbid pain in tinnitus patients to provide a more comprehensive treatment of tinnitus.

Physical activity and cold pain tolerance in the general population.

BACKGROUND: The relationship between habitual physical activity (PA) and experimental pain tolerance has been investigated in small samples of young, healthy and/or single-sex volunteers. We used a large, population-based sample to assess this relationship in men and women with and without chronic pain. METHODS: We used data from the sixth and seventh Tromsø Study surveys (2007-2008; 2015-2016), with assessed pain tolerance of participants with the cold pressor test (CPT: dominant hand in circulating cold water at 3°C, maximum test time 106 s), and self-reported total amount of habitual PA in leisure time (n = 19,087), exercise frequency (n = 19,388), exercise intensity (n = 18,393) and exercise duration (n = 18,343). A sub-sample had PA measured by accelerometers (n = 4,922). We used Cox regression to compare CPT tolerance times between self-reported PA levels. For accelerometer-measured PA, we estimated hazard ratios for average daily activity counts, and for average daily minutes of moderate-to-vigorous PA done in bouts lasting 10 min or more. Models were tested for PA-sex, and PA-chronic pain and PA-moderate-to-severe chronic pain interactions. RESULTS: Leisure-time PA, exercise intensity and exercise duration were positively associated with CPT tolerance (p < .001; p = .011; p < .001). More PA was associated with higher CPT tolerance. At high levels of leisure-time PA and exercise intensity, men had a significantly higher CPT tolerance than women. Accelerometer-measured PA was not associated with CPT tolerance. CONCLUSIONS: This study is one of the first to show that higher self-reported habitual PA was connected to higher experimental pain tolerance in a population-based sample, especially for men. This was not found for accelerometer-measured PA. SIGNIFICANCE: This study finds that higher level of self-reported leisure-time physical activity is associated with increased cold pressor pain tolerance in a large population-based sample. Though present in both sexes, the association is strongest among men. Despite the robust dose-response relationship between pain tolerance and self-reported activity level, no such relationship was found for accelerometer-measured activity, reflecting a possible discrepancy in the aspect of physical activity measured. Though the study design does not permit causal conclusions, the findings suggest that increasing physical activity may increase pain tolerance in the general population.

Physical exercise and chronic pain in university students.

BACKGROUND: Physical inactivity and chronic pain are both major public health concerns worldwide. Although the health benefits of regular physical exercise are well-documented, few large epidemiological studies have investigated the association between specific domains of physical exercise and chronic pain in young adults. We sought to investigate the association between frequency, intensity and duration of physical exercise, and chronic pain. METHODS: Data stem from the SHoT2018-study, a national health survey for higher education in Norway, in which 36,625 fulltime students aged 18-35 years completed all relevant questionnaires. Chronic pain, defined according to the International Classification of Diseases 11th Revision (ICD-11), was assessed with a newly developed hierarchical digital instrument for reporting both distribution and characteristics of pain in predefined body regions. Physical exercise was assessed using three sets of questions, measuring the number of times exercising each week, and the average intensity and the number of hours each time. RESULTS: The majority (54%) of the students reported chronic pain in at least one location, and the prevalence was especially high among women. The overall pattern was an inverse dose-response association between exercise and chronic pain: the more frequent, harder or longer the physical exercise, the lower the risk of chronic pain. Similar findings were generally also observed for the number of pain locations: frequent exercise was associated with fewer pain locations. Adjusting for demographical, lifestyle factors and depression had little effect on the magnitude of the associations. CONCLUSION: Given the many health benefits of regular exercise, there is much to be gained in facilitating college and university students to be more physically active, ideally, thru a joint responsibility between political and educational institutions. Due to the cross-sectional nature of the study, one should be careful to draw a firm conclusion about the direction of causality.

Genetic variation in P2RX7 and pain tolerance.

P2X7 is a nonselective cation channel activated by extracellular ATP. P2X7 activation contributes to the proinflammatory response to injury or bacterial invasion and mediates apoptosis. Recently, P2X7 function has been linked to chronic inflammatory and neuropathic pain. P2X7 may contribute to pain modulation both by effects on peripheral tissue injury underlying clinical pain states, and through alterations in central nervous system processing, as suggested by animal models. To further test its role in pain sensitivity, we examined whether variation within the P2RX7 gene, which encodes the P2X7 receptor, was associated with experimentally induced pain in human patients. Experimental pain was assessed in Tromsø 6, a longitudinal and cross-sectional population-based study (N = 3016), and the BrePainGen cohort, consisting of patients who underwent breast cancer surgery (N = 831). For both cohorts, experimental pain intensity and tolerance were assessed with the cold-pressor test. In addition, multisite chronic pain was assessed in Tromsø 6 and pain intensity 1 week after surgery was assessed in BrePainGen. We tested whether the single-nucleotide polymorphism rs7958311, previously implicated in clinical pain, was associated with experimental and clinical pain phenotypes. In addition, we examined effects of single-nucleotide polymorphisms rs208294 and rs208296, for which previous results have been equivocal. Rs7958311 was associated with experimental pain intensity in the meta-analysis of both cohorts. Significant associations were also found for multisite pain and postoperative pain. Our results strengthen the existing evidence and suggest that P2X7 and genetic variation in the P2RX7-gene may be involved in the modulation of human pain sensitivity.

Cross-sectional study of the differences between measured, perceived and desired body size and their relations with self-perceived health in young adults: The Tromsø Study - Fit Futures 2.

AIMS: The aim of this study was to explore the relationships between measured body size (body mass index (BMI)), perceived body size, weight change wishes and self-perceived health in young adults. METHODS: The participants were recruited from a school-based population study in Norway, the Tromsø Study: Fit Futures 2, carried out in 2012-2013. A total of 629 young women and men (aged 18-23 years) reported on the main variables. The data were collected through weight and height measurements and questionnaires. The analyses were performed with descriptive statistics, the χ2 test and Student's t-test. RESULTS: A total of 20% of the women and 28% of the men were overweight or obese. There were considerable discrepancies between the measured BMI and perceived body size in both sexes. A substantial number of participants wanted to change their weight. Among the 174 women who reported that they were trying to lose weight, as many as 57 (32.8%) had a low normal weight (BMI 18.5-21.9 kg/m2). Correspondingly, among the 66 men who reported that they wanted to gain weight, as many as 19 (28.8%) had a high normal weight (BMI 22-24.9 kg/m2). We found no relation between body size perceptions, weight change wishes and self-perceived health. CONCLUSIONS: Discrepancies between measured and perceived body size and weight change wishes are common findings in young adults. The lack of relation with self-perceived health found in our study is surprising and not easy to interpret. To gain more knowledge about these matters, further research, including both qualitative and quantitative studies, is needed.

Investigating the Burden of Chronic Pain: An Inflammatory and Metabolic Composite.

Background. Chronic pain is associated with increased morbidity and mortality, predominated by cardiovascular disease and cancer. Investigating related risk factor measures may elucidate the biological burden of chronic pain. Objectives. We hypothesized that chronic pain severity would be positively associated with the risk factor composite. Methods. Data from 12,982 participants in the 6th Tromsø study were analyzed. Questionnaires included demographics, health behaviors, medical comorbidities, and chronic pain symptoms. The risk factor composite was comprised of body mass index, fibrinogen, C-reactive protein, and triglycerides. Chronic pain severity was characterized by frequency, intensity, time/duration, and total number of pain sites. Results. Individuals with chronic pain had a greater risk factor composite than individuals without chronic pain controlling for covariates and after excluding inflammation-related health conditions (p < 0.001). A significant "dose-response" relationship was demonstrated with pain severity (p < 0.001). In individuals with chronic pain, the risk factor composite varied by health behavior, exercise, lower levels and smoking, and higher levels. Discussion. The risk factor composite was higher in individuals with chronic pain, greater with increasing pain severity, and influenced by health behaviors. Conclusions. Identification of a biological composite sensitive to pain severity and adaptive/maladaptive behaviors would have significant clinical and research utility.

Experimental comparison of parametric versus nonparametric analyses of data from the cold pressor test.

UNLABELLED: Parametric statistical methods are common in human pain research. They require normally distributed data, but this assumption is rarely tested. The current study analyzes the appropriateness of parametric testing for outcomes from the cold pressor test (CPT), a common human experimental pain test. We systematically reviewed published CPT studies to quantify how often researchers test for normality and how often they use parametric versus nonparametric tests. We then measured the normality of CPT data from 7 independent small to medium cohorts and 1 study of >10,000 subjects. We then examined the ability of 2 common mathematical transformations to normalize our skewed data sets. Lastly, we performed Monte Carlo simulations on a representative data set to compare the statistical power of the parametric t-test versus the nonparametric Wilcoxon Mann-Whitney test. We found that only 39% of published CPT studies (47/122) mentioned checking data distribution, yet 72% (88/122) used parametric statistics. Furthermore, among our 8 data sets, CPT outcomes were virtually always nonnormally distributed, and mathematical transformations were largely ineffective in normalizing them. The simulations demonstrated that the nonparametric Wilcoxon Mann-Whitney test had greater statistical power than the parametric t-test for all scenarios tested: For small effect sizes, the Wilcoxon Mann-Whitney test had up to 300% more power. PERSPECTIVE: These results demonstrate that parametric analyses of CPT data are routine but incorrect and that they likely increase the chances of failing to detect significant between-group differences. They suggest that nonparametric analyses become standard for CPT studies and that assumptions of normality be routinely tested for other types of pain outcomes as well.

Widespread hyperalgesia in adolescents with symptoms of irritable bowel syndrome: results from a large population-based study.

UNLABELLED: Widespread hyperalgesia is well documented among adult patients with irritable bowel syndrome (IBS), but little is known about pain sensitivity among adolescents with IBS. We examined pain sensitivity in 961 adolescents from the general population (mean age 16.1 years), including pain threshold and tolerance measurements of heat (forearm) and pressure pain (fingernail and shoulder) and cold pressor tolerance (hand). Adolescents with IBS symptoms (Rome III criteria) had lower heat pain thresholds compared to controls after adjustments for sex, comorbid pain, and psychological distress (mean difference = -.8 °C; 95% confidence interval [CI] = -1.6 to -.04). Similar results were found for pressure pain threshold at the shoulder (mean difference = -46 kPa; 95% CI = -78 to -13) and fingernail (mean difference = -62 kPa; 95% CI = -109 to -15), and for an aggregate of all 3 threshold measures (z-score difference = -.4; 95% CI = -.6 to -.2), though pressure pain threshold differences were nonsignificant after the final adjustments for psychological distress. No difference of pain tolerance was found between the IBS cases and controls. Our results indicate that adolescents in the general population with IBS symptoms, like adults, have widespread hyperalgesia. PERSPECTIVE: This is the first report of widespread hyperalgesia among adolescents with IBS symptoms in the general population, with lower pain thresholds found to be independent of sex and comorbid pain. Our results suggest that central pain sensitization mechanisms in IBS may contribute to triggering and maintaining chronic pain symptoms.

The role of labor pain and overall birth experience in the development of posttraumatic stress symptoms: a longitudinal cohort study.

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.

Persistent post-surgical pain and experimental pain sensitivity in the Tromsø study: comorbid pain matters.

In a large survey incorporating medical examination (N=12,981), information on chronic pain and surgery was collected, and sensitivity to different pain modalities was tested. Tolerance to the cold pressor test was analysed with survival statistics for 10,486 individuals, perceived cold pressor pain intensity was calculated for 10,367 individuals, heat pain threshold was assessed for 4,054 individuals, and pressure pain sensitivity for 4,689 individuals. Persistent post-surgical pain, defined by self-report, was associated with lower cold pressor tolerance (sex-adjusted hazard ratio=1.34, 95% confidence interval=1.08-1.66), but not when adjusting for other chronic pain. Other experimental pain modalities did not differentiate between individuals with or without post-surgical pain. Of the individuals with chronic pain (N=3352), 6.2% indicated surgery as a cause, although only 0.5% indicated surgery as the only cause. The associations found between persistent post-surgical pain and cold pressor tolerance is largely explained by the co-existence of chronic pain from other causes. We conclude that most cases of persistent post-surgical pain are coexistent with other chronic pain, and that, in an unselected post-surgical population, persistent post-surgical pain is not significantly associated with pain sensitivity when controlling for comorbid pain from other causes. A low prevalence of self-reported persistent pain from surgery attenuates statistically significant associations. We hypothesize that general chronic pain is associated with central changes in pain processing as expressed by reduced tolerance for the cold pressor test.

Five-factor personality traits and pain sensitivity: a twin study.

Factors underlying individual differences in pain responding are incompletely understood, but are likely to include genetic influences on basal pain sensitivity in addition to demographic characteristics such as age, sex, and ethnicity, and psychological factors including personality. This study sought to explore the relationship between personality traits and experimental pain sensitivity, and to determine to what extent the covariances between these phenotypes are mediated by common genetic and environmental factors. A sample composed of 188 twins, aged 23 to 35years, was included in the study. Heat pain intensity (HPI) and cold-pressor pain intensity (CPI) ratings were obtained using standardized pain testing procedures, and personality traits were assessed with the NEO Personality Inventory, Revised. Associations between personality and the pain sensitivity indices were examined using zero-order correlations and generalized estimating equations. Bivariate Cholesky models were used in the biometric analyses. The most robust finding was a significant phenotypic association between CPI and the personality facets Impulsiveness (a facet of Neuroticism) and Excitement-Seeking (a facet of Extraversion), and estimates of the genetic correlation were .37 (P<.05) and .43 (P<.05), respectively. In contrast, associations between HPI and personality seemed weak and unstable, but a significant effect of Angry Hostility (a facet of Neuroticism) emerged in generalized estimating equations analysis. Although the genetic correlation between these phenotypes was essentially zero, a weak but significant individual-specific environmental correlation emerged (re=.21, P<.05). Taken together, these findings suggest that CPI is more consistently related to personality dispositions than HPI, both phenotypically and genetically.

Persistent postsurgical pain in a general population: prevalence and predictors in the Tromsø study.

Population-based data on the prevalence of persistent postsurgical pain are scarce. This study aimed to assess the prevalence of persistent postsurgical pain in a general population and to describe associated physical, social, and psychological factors, including symptoms of nerve injury and sensitization. A cross-sectional survey was performed in northern Norway with questionnaire items covering surgery, pain, and sensory abnormalities in the area of surgery. Of the 12,982 participants, 24.0% (3111) had undergone one or more surgical procedures during the 3 years preceding the survey. Of these, 2043 had the surgery performed more than 3 months before the investigation. Persistent pain in the area of surgery was reported by 40.4% of the patients (826 of 2043), moderate or severe pain by 18.3% (373 of 2043). Hypoesthesia, hyperesthesia, or both was reported by 24.5% (501 of 2043). There were strong associations between sensory abnormalities and persistent pain, increasingly with higher pain intensities; odds ratios were 2.68 for hypoesthesia and 6.27 for hyperesthesia. Of the 826 individuals reporting persistent pain in the anatomical area of surgery, 51.0% reported chronic pain when questioned without specific reference to the surgery. The present study supports evidence from clinical studies of persistent postsurgical pain, indicating a high prevalence, but reveals large discrepancies in report of pain, depending on the questions asked and the context in which the questions are presented. Strong associations between sensory abnormalities and pain indicate neuropathic mechanisms in a major proportion of cases.

Neuroticism and self-reported somatic health: a twin study.

Using a twin sample (N = 188; 53 monozygotic and 39 dizygotic twin pairs, and 4 single twins whose co-twin did not participate), this study sought (1) to estimate heritabilities of neuroticism and of somatic complaints rated on the basis of two different time frames ('the last week' vs. 'in general'); (2) to estimate the genetic association between neuroticism and the complaints indices and (3) to examine to what extent somatic complaints are aetiologically distinct from neuroticism. Using models with common additive genetic (A) and individual-specific environmental (E) factors, the heritabilities for neuroticism and complaints 'in general' and during 'the last week' were 0.46 (0.20-0.65), 0.44 (0.22-0.62), and 0.45 (0.22-0.63), respectively. Nearly 60% of the phenotypic correlation between neuroticism and somatic complaints were accounted for by A. Furthermore, a substantial part of the variance in somatic complaints was due to unique genetic and individual-specific environmental influences unrelated to neuroticism. These results suggest that somatic complaints are moderately heritable and that a considerable portion of the covariance between neuroticism and complaints measures is due to genetic factors. Yet, the findings also suggest that these two attributes are distinct entities with overlapping, but not identical, underlying genetic and environmental influences.