Mariana Wentz Faoro1; Maria Teresa Anselmo Olinto1; Vera Maria Vieira Paniz1; Jamile Macagnan2; Ruth Liane Henn1; Anderson Garcez1; Marcos Pascoal Pattussi1
BACKGROUND: Musculoskeletal pain is one of the most common occupational problems in the industrial society and its prevalence is potentially associated with mental disorders.
OBJECTIVE: To estimate the prevalence of work-related musculoskeletal pain and its association with occurrence of common mental disorders among employees of a poultry processing company in Southern Brazil.
METHODS: Cross-sectional study conducted in 2010 with 1,103 employees aged 18 to 52 years old. Musculoskeletal pain was investigated based on a human figure adapted from the Standardized Nordic Questionnaire. We considered reported work-related pain in any part of the body in the past 12 months. Occurrence of common mental disorders was assessed- by the Self-Reporting Questionnaire (SRQ-20). Crude and adjusted prevalence ratios (PR) and corresponding 95% confidence interval (95%CI) were obtained by Poisson regression with robust variance.
RESULTS: The prevalence of work-related musculoskeletal pain was 40.3% (95%CI 37.4–43.2) for the total sample, 46.8% (95%CI 43.2–50.5) for women and 27.8% (95%CI 23.2–32.3) for men. The prevalence of musculoskeletal pain was twice higher for the participants with common mental disorders compared to those without this condition (PR=2.27; 95%CI 1.99–2.58). This effect remained significant after adjustment for sociodemographic, behavioral, health-related and occupational variables.
CONCLUSION: The results of the present study point to the relevance of preventive measures to promote the mental and physical health of workers in order to reduce or minimize the occurrence of pain.
Keywords: mental health; musculoskeletal pain; occupational health.
CONTEXTO: A dor musculoesquelética é um dos problemas ocupacionais mais comuns nas sociedades industrializadas, e sua prevalência é potencialmente associada à presença de transtornos mentais.
OBJETIVO: Estimar a prevalência de dor musculoesquelética relacionada ao trabalho e sua associação com a presença de transtornos mentais comuns em trabalhadores de um frigorífico do Sul do Brasil.
MÉTODOS: Realizou-se um estudo transversal com o total de 1.103 trabalhadores, de 18 a 52 anos de idade, em 2010. A dor musculoesquelética foi avaliada por meio de uma figura humana adaptada do Questionário Nórdico de Sintomas Osteomusculares. Considerou-se o relato da presença de dor relacionada ao trabalho em qualquer região do corpo nos últimos 12 meses. A presença de transtornos mentais comuns foi determinada pelo Self-Reporting Questionnaire (SRQ-20). Razões de prevalências (RP) brutas e ajustadas, com seus respectivos intervalos de confiança de 95% (IC95%), foram obtidas mediante a regressão de Poisson.
RESULTADOS: A prevalência de dor musculoesquelética relacionada ao trabalho foi de 40,3% (IC95% 37,4–43,2) na amostra geral, 46,8% (IC95% 43,2–50,5) nas mulheres e 27,8% (IC95% 23,2–32,3) nos homens. Na análise bruta, trabalhadores com presença de transtornos mentais comuns apresentaram prevalência duas vezes maior de dor musculoesquelética relacionada ao trabalho quando comparados com aqueles sem transtornos (RP=2,27; IC95% 1,99–2,58). Esse efeito manteve-se significativo após o ajuste para variáveis sociodemográficas, comportamentais, de saúde e ocupacionais.
CONCLUSÃO: Os resultados deste estudo alertam para a importância de medidas visando à promoção da saúde física e mental dos trabalhadores em ações para reduzir a dor.
Palavras-chave: saúde mental; dor musculoesquelética; saúde do trabalhador.
Musculoskeletal disorders are considered a considerable health problem in present-day society for representing the main cause of functional incapacity1,2. These are the conditions that most contribute to occurrence of daily pain among workers, which in addition to biological and psychological harm, is also a cause of incapacity for work3.
Musculoskeletal pain is characterized by the occurrence of several concomitant symptoms, such as paresthesia, heaviness and physical fatigue, which characteristics vary as a function of the location, etiology, intensity and frequency of pain4. However, the presence of these symptoms only does not necessarily imply occurrence of some musculoskeletal disease5.
When related to work, musculoskeletal pain tends to vary as a function of the job characteristics6, and occurrence is potentially associated with mechanical or psychosocial factors7. Biomechanical factors mainly include repetitive movements, remaining in the same position over a long period of time and trunk rotation8. In turn, psychosocial factors mainly comprise high job demands, lack of autonomy and accelerated rhythm of production9,10. In addition to limitations and incapacity for work, pain might also influence and impair the activities of daily living and quality of life of workers3.
Common mental disorders are a set of symptoms that includes irritability, fatigue, insomnia, difficult concentration, memory deficit, physical complaints and anxiety and depression symptoms11. Several studies reported higher frequency of musculoskeletal pain among individuals with minor mental disorders, which thus points to a possible relationship between pain and mental health10,12,13. While the causal pathways that link mental health and musculoskeletal pain together have not yet been fully elucidated, this relationship is probably due to biological mechanisms, such as action of neurotransmitters. The reason is that some individuals are more aware of their symptoms and more predisposed to report them, or that individuals with mental disorders tend to be more concerned with their health and thus pay more attention to pain13.
Most studies on this subject were mainly conducted in developed countries4,7,10. Publications are fewer in Brazil and focused on aspects related to healthcare professionals’ work14.
Therefore, the aim of the present study was to investigate the prevalence of work-related musculoskeletal pain and its association with common mental disorders in a sample of employees of a poultry processing company in Southern Brazil.
The present cross-sectional and epidemiological study was conducted with 1,103 employees aged 18 to 52 years of a poultry processing company in Southern Brazil. These data were collected within the context of a larger research project that investigated several health outcomes, including noncommunicable diseases, behavioral and mental health habits and work-related musculoskeletal disorders among employees of a poultry processing company.
The investigated company is located in a small town in Southern Brazil which operates 24/7. It comprises 2,645 employees from both sexes who live in this same or six other neighboring towns. The initial sample size was calculated based on outcomes excess weight and abdominal obesity. For the present study power was calculated a posteriori based on prevalence of work-related musculoskeletal pain of 70% in the exposed group (with common mental disorders) and ratio 3:1 of non-exposed to exposed. Therefore, the effective sample size (n=1,103) resulted in 80% of statistical power and 95% of confidence for analysis of associations with relative risk of 1.17 or higher.
To reach this number of participants and due to logistic reasons, we selected only the employees who lived in the town where the company is located and two neighboring towns and worked in the main three production line points: evisceration, cut-up and deboning and thermoprocessed products (n=1,278). The corresponding activities demand remaining in the same position and perform repetitive movements most of the time and impose work overload. Along the sampling process 103 workers were excluded, to wit: the ones on leave for any reason for more than 10 days, women in any stage of pregnancy and employees hired less than 12 months earlier. The number of participants lost along the study — including the ones laid off or who had moved to another town not considered in the study — was low (n=72). None of the selected employees refused participation.
Structured interviews were performed at the participants’ homes by municipal community health agents in 2010. For this purpose the agents participated in a training program which emphasized standardization in the application of instruments and adequate interview techniques. The questionnaire included closed-ended questions and was standardized, pre-encoded and pretested. Quality control for investigation of the consistency of the data collected on fieldwork was based on a second interview with 10% of the sample selected by means of the lottery method. The quality control instrument was similar to the one used in the main study, with variables without temporal variation which showed satisfactory repeatability (Kappa>0,7).
Outcome work-related musculoskeletal pain was assessed using a validated human figure adapted from the Standardized Nordic Questionnaire (SNQ)15. This figure, divided in nine anatomical areas, was shown during interviews to the participants, who were requested to indicate the location of pain. This outcome was defined as self-reported occurrence of musculoskeletal pain in any part of the body often or all the time in the past 12 months. Association between self-reported pain and job activities was investigated through question: “Considering the answer you gave to the picture (SNQ figure) in which case(s) do you believe the symptom(s) is(are) related to work?”
Presence of common mental disorders, i.e., the main investigated exposure, was analyzed by means of the Self-Reporting Questionnaire (SRQ-20). This is a self-report instrument widely used for early detection of signs and symptoms of non-psychotic mental disorders. It comprises 20 close-ended questions with dichotomous response options (yes/no) meant for screening for depression, anxiety, insomnia, fatigue, irritability, forgetfulness, difficulty concentrating and physical complaints in the past 30 days. SRQ-20 was validated for the Brazilian Portuguese language16. Cutoff points per sex (men: 6; women: 7) were used to define presence or absence of common mental disorders. This instrument is also efficient to investigate mental health in the workplace17.
Explanatory variables collected and analyzed as potential confounding factors were: demographic (sex, age, skin color and marital status), socioeconomic (educational level and family income), behavioral (alcohol consumption, smoking and physical activity), health related (nutritional status and self-perceived health) and occupational (temperature at job area and length of work in the company). Variables family income and educational level were self-reported and defined as times the equivalent of the minimum wage and completed years of formal education, respectively. Participants who performed physical activity, independently from its intensity, for a minimum of 150 minutes per week in leisure time or as means of transportation were categorized as physically active. Alcohol consumption was investigated as beverage type and amount and categorized based on daily intake (does not drink; mild to moderate: <15 d/day for women and <30 g/day for men; high: =15 g/day for women and =30 g/day for men). Nutritional status was assessed according to the body mass index (BMI) and cutoff points recommended by the World Health Organization (WHO): normal (BMI <25 kg/m2), overweight (BMI 25 to 29 kg/m2) and obesity (IMC=30 kg/m2). BMI was calculated with the body weight and height through equation: weight (kg) divided by height (m) squared.
The data were entered in program EpiData version 3. The responses given to the questionnaire were entered twice and compared to identify and correct eventual errors. Data processing and statistical analysis were performed with software Statistical Package for the Social Sciences (SPSS) for Windows version 18.0 and Stata version 11.0.
Descriptive statistics was performed to investigate the general distribution of the sample and the outcome distribution, which were expressed as absolute and relative frequencies. Associations between independent variables and outcome work-related musculoskeletal pain were investigated by means of Pearson’s χ2 test. Poisson regression with robust variance was used to estimate crude and adjusted prevalence ratios (PR) with the corresponding 95% confidence interval (95%CI).
To investigate and demonstrate the consistency of the association between common mental disorders and work-related musculoskeletal pain we fit two models on adjusted (multivariate) analysis. The first involved backward analysis: demographic, socioeconomic, behavioral, health-related and occupational variables considered to be confounding factors were excluded one by one, and only the ones with less than 5% of statistical significance remained in the final model (sex, skin color, self-perceived health and alcohol consumption). In the second model, the effect of variable presence of common mental disorders on occurrence of musculoskeletal pain was controlled for all the investigated demographic, socioeconomic, behavioral, health-related and occupational variables independently from their statistical significance. Analyses were performed for the total sample and stratified per sex.
The study was submitted to and approved by the research ethics committee of University of the Sinos River Valley (Universidade do Vale do Rio dos Sinos – UNISINOS) and registered in the National System of Information on Ethics in Research with Human Beings (Sistema Nacional de Informação sobre Ética em Pesquisa envolvendo Seres Humanos – SISNEP) identification number FR 266144 and Certificate of Presentation for Ethical Appraisal (Certificado de Apresentação para Apreciação Ética – CAAE) no. 2014.0.000.390-09. All the participants signed an informed consent form, at which time they were informed of the voluntary nature of participation and that anonymity was ensured.
All 1,103 employees were included for analysis. Their average age was 30 years old — standard deviation (SD)=2.4. About 65.7% of the participants were female, most were white (83.8%) and about 70% did not have a partner. The average income was 2.5 (SD=1.1) times the equivalent of the minimum wage. The participants had 6.7 years (SD=2.0) of formal education, on average. About 85% of the sample rated their health excellent/very good/good and 3.2% reported excessive alcohol consumption (Table 1).
The mean BMI was de 24.6 kg/m2 (SD=11) and more than half of the sample (64.7%) exhibited normal weight. About 85% of the participants had never smoked and 63.8% were rated as physically inactive. About 84% of the participants worked at a temperature below 12ºC. More than half of the sample had worked up to 60 months in the company.
The prevalence of work-related musculoskeletal pain was 40.3% (95%CI 37.4–43.2) for the total sample, 46.8% (95%CI 43.2–50.5) for the women and 27.8% (95%CI 23.2–32.3) for the men. The frequency of common mental disorders was 24.1% (95%CI 21.6–26.8) for the total sample and was higher for the women compared to the men (Table 1).
Table 1 describes the results relative to prevalence of work-related musculoskeletal pain for the total sample. The data are stratified according to sociodemographic, behavioral, health-related and occupational characteristics. The prevalence of musculoskeletal pain was significantly higher among the participants who rated their state of health reasonable or poor (negative perceived health) being similar between men and women. The prevalence of musculoskeletal pain was higher for white women and women who reported higher alcohol consumption.
In regard to the main association investigated in the present study, unadjusted analysis showed that the prevalence of musculoskeletal pain was twice higher among the participants with common mental disorders compared to the ones without this condition (PR=2.27; 95%CI 1.99–2.58). On analysis stratified per sex, the outcome prevalence was almost 2.6 times higher for the men (PR=2.59; 95%CI 1.91–3.52) and twice higher for the women (PR=2.01; 95CI 1.75–2.32) with common mental disorders compared to the ones without this condition (Table 2). Following adjustment for potential confounding factors, PR was about twice higher for employees with common mental disorders compared to the ones without this condition for the total sample and also on analysis stratified per sex. This effect remained independently from the adjustment model considered (Table 2). The effect of presence of common mental disorders on musculoskeletal pain was greater for the men.
In the present study, we detected high prevalence of musculoskeletal pain among the investigated sample, more particularly among the women. Following adjustment for confounding factors significant association was found between musculoskeletal pain and occurrence of common mental disorders. The prevalence of work-related musculoskeletal pain was about twice higher for the participants with common mental disorders compared to the ones without this condition.
The prevalence of work-related musculoskeletal pain found in the present study was similar to the one reported in previous research with the same category of workers (meatpacking industry employees)18. However, the rates found for other categories of workers, such as nursing professionals and plastics industry employees, were different14,19. This difference might be mainly attributed to the type and specificity of the respective job activities20, including, e.g., ergonomic characteristics, body position, movements performed and taking rest breaks or not.
The prevalence of musculoskeletal pain was higher for the women compared to the men. This finding are consistent with the results of previous studies19,21. The literature attributes this difference between sexes mainly to the characteristics of work. Several studies found that job activities performed by women are usually more repetitive, given less value and develop under more rigid control and more difficult conditions compared to the ones performed by men22,23. These characteristics are also constantly associated to suffering and mental illnesses24,25. In addition to occupational characteristics, previous studies pointed to other factors that might contribute to this difference between sexes, such as biomechanical characteristics of the body26, adaptation to muscle pain27,28, social differences and performance of household chores29.
Among the main findings, we also detected higher prevalence of common mental disorders among the women compared to the men. This situation was also reported in other studies that applied the same measurement instrument, however, to other population groups6,30. The association between common mental disorders and work-related musculoskeletal pain was stronger for the men. This is to say, this association was more robust for the men compared to the women. However, it should be observed that the confidence interval was narrower for the women in all the measurements, which denotes less variability (i.e., measurements are more accurate as a function of the larger sample size). These findings allow hypothesizing that although the pain threshold is higher for men compared to women, the latter might be more tolerant and resilient. Resilience is the ability to perceive and adapt to adversities in life and control and cope with problems which might have negative impact on health31.
The present is one of the first studies that investigated a possible relationship between common mental disorders and work-related musculoskeletal pain among poultry processing industry employees. We found significant association between common mental disorders and work-related musculoskeletal pain. Similar findings were reported in several previous studies4,7,10,12,13. This association might be explained by biological and mechanical factors. The biological factors that account for the occurrence of musculoskeletal pain among individuals with common mental disorders involve descending pathways of the central nervous system (CNS)32. Nociceptive neurons transmit pain signals from peripheral areas to the brain through the spinal cord. A modulatory system directly related to this transmission system seeks to protect the body from external threats by attenuating internal signals to the point of suppressing them, while the external signals are enhanced. However, as a function of the serotonin and norepinephrine depletion that occurs in individuals with mental disorders, this system tends to loss its modulatory effect, and the internal signals consequently increase33,34.
In regard to the mechanical factors, repetitive movements performed by workers in their workstations lead to sensitization of the peripheral nociceptive neurons, which causes a feeling of pain known as hyperalgesia that usually ceases when inflammation disappears32. However, repeated injury might result in allodynia, which is characterized by a form of dysfunction of the brain activity that manifests as pain even though the underlying stimulus is not painful35. The reason might be that the message transmitted by the afferent nerve fibers is abnormal, and as a result they may trigger or worsen anxiety or depression symptoms, for instance.
The present study had cross-sectional design, which main advantages include fast execution and low cost, in addition to being useful for the formulation of research questions. However, it also behaved as a limitation, as the data were collected at a single time-point. As a result, the association found in the present study is pervaded by the temporal uncertainty of the analyzed variables, and we are not able to establish whether common mental disorders favor the occurrence of musculoskeletal pain or worsen it. Studies with prospective design might elucidate better the association investigated in the present study.
Occurrence of musculoskeletal pain and common mental disorders was self-reported and thus susceptible to information bias. In addition, the results should be interpreted in the light of the healthy worker effect, as employees on leave for more than 10 days were excluded from the study, thus possibly leading to underestimation of the analyzed prevalence rates. Among the strengths of the present study we might mention the sample size and low rate of refusals to participation. One further aspect that reinforces the internal validity of the present study is the application of instruments widely used in published scientific studies, translated to the Portuguese language and validated for use in Brazil. Finally, the results have satisfactory consistency given that two multivariate models were fit and the analyses were stratified per sex.
In the present study, we detected high prevalence of musculoskeletal pain among the analyzed sample, the women in particular. Following adjustment for potential confounding factors we found significant association between musculoskeletal pain and occurrence of common mental disorders. The results showed that the prevalence of work-related musculoskeletal pain was about twice higher among the participants with common mental disorders compared to the ones without this condition. Considering the setting within which the present study was conducted, the results point to the relevance of preventive measures to reduce the occurrence of musculoskeletal pain and improve the mental health of workers.
1. Storheim K, Zwart JA. Musculoskeletal disorders and the Global Burden of Disease study. Ann Rheum Dis. 2014;73(6):949-50. https://doi.org/10.1136/annrheumdis-2014-205327
2. Azambuja M. Dor osteomuscular crônica - problema de saúde pública que requer mais prevenção e nova abordagem clínica e previdenciária? Rev Bras Med Trab. 2012;10(1):129-31.
3. Björnsdóttir SV, Jónsson SH, Valdimarsdóttir UA. Functional limitations and physical symptoms of individuals with chronic pain. Scand J Rheumatol. 2013;42(1):59-70. https://doi.org/10.3109/03009742.2012.697916
4. Shaw WS, Means-Christensen A, Slater MA, Patterson TL, Webster JS, Atkinson JH. Shared and independent associations of psychosocial factors on work status among men with subacute low back pain. Clin J Pain. 2007;23(5):409-16. https://doi.org/10.1097/AJP.0b013e31804eff30
5. Oliveira FAC, Almeida RS, Santos WT, Nogueira LAC. A intensidade da dor e a limitação funcional não estão relacionadas com os achados em imagens de pacientes com dor no ombro. Rev Dor. 2014;15(3):202-6. http://dx.doi.org/10.5935/1806-0013.20140044
6. Greco PBT, Magnago TSBS, Urbanetto JS, Luz EMF, Prochnow A. P revalência de distúrbios psíquicos menores em agentes socioeducadores do Rio Grande do Sul. Rev Bras Enferm. 2015;68(1):93-101. http://dx.doi.org/10.1590/0034-7167.2015680113p
7. Smith DR, Wei N, Zhao L, Wang RS. Musculoskeletal complaints and psychosocial risk factors among Chinese hospital nurses. Occup Med (Lond). 2004;54(8):579-82. https://doi.org/10.1093/occmed/kqh117
8. Hales TR, Bernard BP. Epidemiology of work-related musculoskeletal disorders. Orthop Clin North Am. 1996;27(4):679-709.
9. Haukka E, Leino-Arjas P, Ojajärvi A, Takala EP, Viikari-Juntura E, Riihimäki H. Mental stress and psychosocial factors at work in relation to multiple-site musculoskeletal pain: a longitudinal study of kitchen workers. Eur J Pain. 2011;15(4):432-8. https://doi.org/10.1016/j.ejpain.2010.09.005
10. Solidaki E, Chatzi L, Bitsios P, Markatzi I, Plana E, Castro F, et al. Workrelated and psychological determinants of multisite musculoskeletal pain. Scand J Work Environ Health. 2010;36(1):54-61.
11. Goldberg D. A bio-social model for common mental disorders. Acta Psychiatr Scand Suppl. 1994;385:66-70.
12. Björnsdóttir SV, Jónsson SH, Valdimarsdóttir UA. Mental health indicators and quality of life among individuals with musculoskeletal chronic pain: a nationwide study in Iceland. Scand J Rheumatol. 2014;43(5):419-23. https://doi.org/10.3109/03009742.2014.881549
13. Vargas-Prada S, Coggon D. Psychological and psychosocial determinants of musculoskeletal pain and associated disability. Best Pract Res Clin Rheumatol. 2015;29(3):374-90. https://doi.org/10.1016/j.berh.2015.03.003
14. da Rocha Vidor C, Mahmud MAI, Farias LF, Silva CA, Ferrari JN, Comel JC, et al. Prevalência de dor osteomuscular em profissionais de enfermagem de equipes de cirurgia em um hospital universitário. Acta Fisiátrica. 2014;21(1):6-10. https://doi.org/10.5935/0104-7795.20140002
15. Pinheiro FA, Troccoli BT, Carvalho CV. Validação do Questionário Nórdico de Sintomas Osteomusculares como medida de morbidade. Rev Saúde Pública. 2002;36(3):307-12. http://dx.doi.org/10.1590/S0034-89102002000300008
16. Mari JJ, Williams P. A validity study of a psychiatric screening questionnaire (SRQ-20) in primary care in the city of Sao Paulo. Br J Psychiatry. 1986;148:23-6.
17. Guirado GMP, Pereira NMP. Uso do Self-Reporting Questionnaire (SRQ-20) para determinação dos sintomas físicos e psicoemocionais em funcionários de uma indústria metalúrgica do Vale do Paraíba/SP. Cad Saúde Coletiva. 2016;24(1):92-8. http://dx.doi.org/10.1590/1414-462X201600010103
18. Soares ACC. Estudo retrospectivo de queixas musculosesqueléticas em trabalhadores de frigorífico [dissertação de mestrado]. Florianópolis: Programa de Pós-graduação em Engenharia de Produção, Universidade Federal de Santa Catarina; 2004.
19. Almeida CGT, Fernandes RCP. Distúrbios musculoesqueléticos em extremidades superiores distais entre homens e mulheres: resultados de estudo na indústria. Rev Bras Saúde Ocup. 2017;42(e3). http://dx.doi.org/10.1590/2317-6369000125515
20. Silva-Junior J, Buzzoni G, Morrone L. Queixas osteomusculares dos trabalhadores e condições biomecânicas no trabalho em metalúrgica de alumínio. Rev Bras Med Trab. 2016;14(2):115-9. http://dx.doi.org/10.5327/Z1679-443520160215
21. Wijnhoven HA, de Vet HC, Picavet HS. Prevalence of musculoskeletal disorders is systematically higher in women than in men. Clin J Pain. 2006;22(8):717-24. https://doi.org/10.1097/01.ajp.0000210912.95664.53
22. Salim CA. Doenças do trabalho: exclusão, segregação e relações de gênero. São Paulo Perspec. 2003;17(1):11-24. http://dx.doi.org/10.1590/S0102-88392003000100003
23. Oliveira EM, Barreto M. Engendrando gênero na compreensão das lesões por esforços repetitivos. Saúde Soc. 1997;6(1):77-99. http://dx.doi.org/10.1590/S0104-12901997000100006
24. Bilsker D. Mental health care and the workplace. Can J Psychiatry. 2006;51(2):61-2.
25. Alcântara MA, Assunção AA. Influência da organização do trabalho sobre a prevalência de transtornos mentais comuns dos agentes comunitários de saúde de Belo Horizonte. Rev Bras Saúde Ocup. 2016;41(e2). http://dx.doi.org/10.1590/2317-6369000106014
26. Côté JN. A critical review on physical factors and functional characteristics that may explain a sex/gender difference in workrelated neck/shoulder disorders. Ergonomics. 2012;55(2):173-82. https://doi.org/10.1080/00140139.2011.586061
27. Leresche L. Defining gender disparities in pain management. Clin Orthop Relat Res. 2011;469(7):1871-7. https://doi.org/10.1007/s11999-010-1759-9
28. Alabas OA, Tashani OA, Tabasam G, Johnson MI. Gender role affects experimental pain responses: a systematic review with meta-analysis. Eur J Pain. 2012;16(9):1211-23. https://doi.org/10.1002/j.1532-2149.2012.00121.x
29. Arcas MM, Novoa AM, Artazcoz L. Gender inequalities in the association between demands of family and domestic life and health in Spanish workers. Eur J Public Health. 2013;23(5):883-8. https://doi.org/10.1093/eurpub/cks095
30. da Silva MC, Fassa AG, Kriebel D. Minor psychiatric disorders among Brazilian ragpickers: a cross-sectional study. Environ Health. 2006;5:17. https://doi.org/10.1186/1476-069X-5-17
31. Rutter M. Resilience as a dynamic concept. Dev Psychopathol. 2012;24(2):335-44. https://doi.org/10.1017/S0954579412000028
32. Holdcroft A, Jaggar S. Core topics in pain. Cambridge: Cambridge University Press; 2005.
33. Fauci AS, Braunwald E, Dennis LK, Stephen LH, Lonho DL, Jameson JL, et al. Harrison’s principles of internal medicine. 17ª ed. Estados Unidos: McGraw Hill; 2008.
34. Okada K, Murase K, Kawakita K. Effects of electrical stimulation of thalamic nucleus submedius and periaqueductal gray on the visceral nociceptive responses of spinal dorsal horn neurons in the rat. Brain Res. 1999;834(1-2):112-21.
35. Hucho T, Levine JD. Signaling pathways in sensitization: toward a nociceptor cell biology. Neuron. 2007;55(3):365-76. https://doi.org/10.1016/j.neuron.2007.07.008
19 de Dezembro de 2017.
Aceito em 26 de Maio de 2018.
Fonte de financiamento: Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) processos 477069/2009-6 e 307257/2013-4