The main objective of this study is to review and summarize recent findings on electroencephalographic patterns in individuals with chronic pain. We also discuss recent advances in the use of quantitative Electroencephalography (qEEG) for the assessment of pathophysiology and biopsychosocial factors involved in its maintenance over time. Data collection took place from February 2014 to July 2015 in PubMed, SciELO and PEDro databases. Data from cross-sectional studies and longitudinal studies, as well as clinical trials involving chronic pain participants were incorporated into the final analysis. Our primary findings related to chronic pain were an increase of theta and alpha EEG power at rest, and a decrease in the amplitude of evoked potentials after sensory stimulation and cognitive tasks. This review suggests that qEEG could be considered as a simple and objective tool for the study of brain mechanisms involved in chronic pain, as well as for identifying the specific characteristics of chronic pain condition. In addition, results show that qEEG probably is a relevant outcome measure for assessing changes in therapeutic studies.

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OBJECTIVE:To estimate the prevalence of chronic pain, identifying the associated factors. METHODS:A cross-sectional study was conducted in a population sample of 2,297 individuals aged 20 years or more, in Salvador, Northeastern Brazil, in 1999 and 2000. A standardized questionnaire was administered at the individuals' home to collect data about pain, sociodemographic characteristics, and abdominal circumference measurement. The criterion for chronic pain classifi cation was duration above six months. Prevalence of pain was estimated by adjusted prevalence ratio with confi dence interval of 95% and p<0.05 for the univariate analyses and logistic regression. RESULTS:The presence of chronic pain was found in 41.4% of the population. In the gross analysis, the most frequent associated factors were: sex, age, marital status, smoking and alcohol consumption (p<0.05). In the multivariate analysis, female sex, age, smoking and presence of central obesity were independent predictors, while moderate consumption of alcohol and being single were protectors. CONCLUSIONS:The presence of chronic pain was predominant in women, elderly individuals, obese individuals, smokers and ex-smokers. Preventive public health strategies are suggested, aiming to disseminate the risks of smoking and obesity for the development of chronic pain. In addition, the periodic monitoring of health is encouraged.

Chronic pain (CP) is prevalent worldwide. Current reports on its prevalence in developing countries are heterogeneous, and to date, there is no quantitative synthesis providing a general estimation of its magnitude in the developing world. The goal of this study was to estimate the pooled prevalence of CP in the general population in developing countries. This was a PROSPERO-registered CRD42019118680 systematic review including population-based cross-sectional studies on CP from countries with ≤0.8 human developing index. We calculated prevalence using both random effects and fixed effects. Heterogeneity was calculated by the Cochran Q test and the I2 statistic. Publication bias was evaluated by visual inspection of the Egger funnel plot, as well as by the Begg rank test and the Egger linear test. Sources of heterogeneity were also explored in subgroup analyses. Twelve studies with a total of 29,902 individuals were included in this meta-analysis, of which 7263 individuals were identified with CP. The overall pooled prevalence of CP after correction for publication bias was 18% (95% confidence interval: 10%–29%), the sample presenting significant heterogeneity (I2 = 100%, P < 0.001). Subgroup analyses demonstrated that year of publication and the adopted threshold for pain chronicity could partially explain the observed heterogeneity (P < 0.05). The proportion of individuals with CP in the general population of developing countries was 18%. However, reports of prevalence have high variability, especially related to year of publication and the threshold level adopted for pain chronicity.