BACKGROUND AND OBJECTIVES:The prevalence of chronic pain has been increasing in the world, and it is considered the most underestimated health care problem impacting the quality of life. Furthermore, there is little consensus regarding the burden of chronic pain in Brazil. The present study aimed to investigate the prevalence of chronic pain in the general Brazilian adult population, and the socio-demographic, clinical, medical conditions and pain locations on the body. METHODS: A cross-sectional Internet-based survey was conducted in a nationally representative sample of Brazil adults to estimate the prevalence, sociodemographic correlates and characteristics of chronic pain in the Brazilian population. Twenty--seven-thousand and three hundred forty-five (27,345) representative residents were contacted. RESULTS: From 27,345 individuals, 20,830 (76.17%) presented chronic, recurrent, or long-lasting pain, lasting for at least 6 months. Nearly half of the respondents were 65 years older (48.15%) and the prevalence was higher in females (84,60%) than males (16.40%). The prevalence of primary chronic lower back pain was 59.85%; of primary rheumatoid arthritis was (59.78%) and primary osteoarthritis pain was 69.02%. Half of the respondents with chronic pain experienced daily pain, and average (past 3 months) pain intensity was moderate at 57.28%. CONCLUSION: Chronic pain affects more than two-thirds of the population of Brazil. Our findings revealed a high prevalence and severity of chronic pain and suggested that it is a public health problem in Brazil. Risk factors are being a woman, advanced age and low levels of household income. There is a need for improved health policies in Brazil for patients with chronic pain. RESUMO JUSTIFICATIVA E OBJETIVOS:A prevalência de dor crônica tem aumentado no mundo e é considerada o problema de saúde mais subestimado, com impacto na qualidade de vida. Além disso, há pouco consenso em relação à carga da dor crônica ao sistema de saúde no Brasil. O presente estudo teve como objetivo investigar a prevalência de dor crônica na população adulta geral brasileira e as condições sociodemográficas, clínicas, médicas e a localização corporal da dor. METODOS: Foi realizado um estudo transversal, em questionário pela internet em uma amostra nacionalmente representativa de adultos do Brasil, para estimar a prevalência e características da dor crônica na população brasileira. Vinte e sete mil e trezentos e quarenta e cinco (27.345) residentes representativos foram contatados. RESULTADOS: Dos 27.345 indivíduos, 20.830 (76,17%) apresentaram dor crônica, recorrente ou duradoura com duração de pelo menos 6 meses. Quase metade dos entrevistados tinham mais de 65 anos de idade (48,15%) e a prevalência era maior nas mulheres (84,60%) do que nos homens (16,40%). A prevalência de dor lombar crônica primária foi de 59,85%; de artrite reumatoide primária foi (59,78%) e dor primária oriunda de osteoartrite foi de 69,02%. Metade dos entrevistados com dor crônica apresentava dor diária e a intensidade da dor...

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The objective of this study was to compare the effects of one or multiple sessions of electroacupuncture (EA) in patients with chronic low back pain. The outcome measures were visual analog score (VAS), pressure pain threshold (PPT), McGill pain questionnaire (MPQ), Roland Morris disability questionnaire (RMDQ), low back skin temperature, surface electromyography of longissimus muscle (contraction/rest) and blood cytokines. After examination (AV0), patients were submitted to EA (2 Hz, 30 minutes, bilaterally at the SP6, BL23, BL31, BL32, BL33, and BL60) and were revaluated after one week (AV1). Patients with VAS <3 (VAS <3 group, n = 20) were directed to return after three weeks (AV2). Patients with VAS >3 (VAS >3 group, n = 20) were submitted to one weekly EA-treatment and revaluated after three weeks (AV2). The VAS <3 group showed a significant reduction in VAS and MPQ and increased PPT in AV1, but not in AV2. No significant differences were found in RMDQ. The VAS >3 group showed reduction in VAS and increased PPT in AV1 and a reduction in MPQ and RMDQ only in AV2. No significant differences were found in electromyography, temperature or cytokines. Thus, despite 2Hz-EA is effective reducing low back pain, some patients only experienced reduced pain intensity and improved functional capacity after full treatment.

The present study evaluates whether the injection of serotonin, acetylcholine, glutamate, bradykinin, histamine, or substance P (SP) into the Zusanli (Stomach 36, ST 36) acupoint can also produce the acupuncture-induced antinociceptive effect on inflammatory or neuropathic pain. In this in vivo experimental study, a total of 450 male Swiss mice were used. Mice were injected with saline or complete Freund's adjuvant (CFA) or subjected to sham or chronic constriction injury (CCI) surgery. After the establishment of the inflammatory (4 hours) or the neuropathic pain (3 days), the animals (n = 6) received manual acupuncture, sham acupuncture, or injection of saline, serotonin, acetylcholine, glutamate, bradykinin, histamine, or SP into the ST 36 and were evaluated for up to 24 hours. Mechanical threshold was evaluated, and the L4-L6 dorsal root ganglion was used for analysis of the transient receptor potential vanilloid type 1 overexpression. The mice from both the CFA and CCI models treated with manual acupuncture had significant increases in the thresholds for more than 24 hours. Sham acupuncture stimulation did not change the thresholds. In the mice injected with each of the mediators, the thresholds were significantly increased for all times in both the CFA and CCI models. Transient receptor potential vanilloid type 1 overexpression in CFA and CCI mice was reduced at all times by injection of serotonin, acetylcholine, or SP but not by injection of glutamate, histamine, or bradykinin. Our data suggest that the neuroactive mediators released by acupuncture-induced tissue injury may contribute to acupuncture-induced analgesia.

Background and aims Newborn infants are vulnerable to procedural stress and pain exposure on the first weeks of life that represents a critical period for the development of nociceptive, sensory, emotional, and social functions. We evaluated the nociceptive behavior of adult male and female rats that were submitted to nociceptive experience in the neonatal period and the maternal behavior in the postnatal period. Methods The animals were submitted to repetitive needle pricking from the second to the fifteenth postnatal day (PND 2–15). Maternal behavior and litter weight were evaluated during this period. Mechanical sensitivity to pain was assessed in offsprings during the adulthood by exposing them to inflammatory stimuli, including formalin test or the Freund's complete adjuvant (CFA) injection followed by the electronic von Frey test at 0, 3, 6 and 24 h later. Results Maternal behavior and litter weight were not altered by pinprick stimuli during PND 2–15. Additionally, pinprick stimulation reduced the paw withdrawal threshold in CFA‐injected animals compared to control. In the formalin test, there was a difference between the genders. Female rats are statically more sensitive to formalin stimulation and showed an increased licking time in both the first and second phases and increased number of flinches in second phase. Conclusions Experiencing early life repetitive pain exposure increased inflammatory pain sensitivity in adult offspring rats and female rats are more sensitive to chemical stimulation. Implications Future investigations of the mechanisms involved in this effect may contribute to the improvement of the understanding of inflammatory pain sensitivity differences.