Work-Related Musculoskeletal Disorders and the Relationship to Ethnicity Work-Related Musculoskeletal Disorders and the Relationship to Ethnicity

Work‐related musculoskeletal disorders (MSDs) are a constellation of painful disorders, which could cause chronic disability. Multiple risk factors, both occupational and non occupational, may be involved. MSDs have been extensively studied in several countries; however, few studies have been carried out based on the relationship between MSDs and ethnicity. Objective: To describe the relationship between MSDs and ethnicity in different parts of the world. Methods: A nonsystematic literature review of studies, with both quantitative and quali‐ tative methodology, was conducted. Results: The evidence in research, qualitative and quantitative, emphasizes the impor‐ tance of this problem in vulnerable populations in different parts of the world, prioritiz ‐ ing migration to developed countries and precarity condition of work. Conclusion: Recommendations for a multidisciplinary approach of MSDs in vulnerable groups were raised.


Introduction
Work-related musculoskeletal disorders (MSDs) are a constellation of painful disorders of muscles, tendons, joints and nerves, which can affect all body parts, although neck, upper limbs and back are the most common areas. Upper extremity musculoskeletal disorders are MSDs cause a huge socioeconomic burden to patients and their household, society and their country indeed. Yet, their relevance is often minimized, particularly in developing countries with fragmented healthcare system and poor nations.
MSDs have been extensively studied in several countries; however, few studies have been carried out so as to investigate the relationship between MSDs and ethnicity [4][5][6][7][8][9].
The main objective of this chapter is to describe the relationship between MSDs and ethnicity in different parts of the world.

Material and methods
A nonsystematic literature review of studies, with both quantitative and qualitative methodology, was conducted. Methodological phases proposed by Greenhalgh et al. [10] were in the following (Figure 1):

Results
Our findings fall into two categories: 1. Summary and analysis of quantitative studies and 2. Synthesis and interpretation of qualitative studies 1. Summary and analysis of quantitative studies ( Table 1): The literature is mostly of European and American origin. They emphasize that certain population groups, especially immigrants and those belonging to lower socioeconomic status, have more MSDs.
In 1998, Urwin et al. [11] describes that people who live in socially deprived areas in United Kingdom (UK) have more musculoskeletal symptoms. Mergler [12] in Canada prioritizes the combination of qualitative and quantitative methods for this complex problem.  Program for the Control of Rheumatic Diseases (COPCORD). In the first case, people living in urban area had less prevalence of MSK diseases, in comparison to the people in rural area. In the second case, the musculoskeletal complaints were more frequent in Turks than in Caucasians, both living in identical environment.
In United States (US), several papers have been published on this topic, especially on immigrant population. In this sense, Schulz et al. [5] describes that the back symptoms and wrist/ hand symptoms were reported by over 35% of Latino workers. In the same way, Rosenbaum et al. [6] identifies that upper body musculoskeletal and low back pain are common in immigrant Latino workers and may negatively impact long-term health and contribute to occupational health disparities. Xiao et al. [8] and Cartwright et al. [9] describe the Latino population as a vulnerable group for MSDs.
In Latin American (LA), previous studies have shown that people belonging to an indigenous group are associated with the prevalence of rheumatic disease as the rheumatoid arthritis (RA) [28]. Due to the presence in LA of indigenous groups, all countries and their condition of vulnerability, not only socioeconomic but also ethnic, were created the Latin American Group for the Study of Rheumatic Diseases in Original Populations (Grupo Latino Americano De estudio de Enfermedades Reumáticas en Pueblos Originarios; GLADERPO). The main objective was to carry out epidemiological, anthropological and genetic studies, thus fulfilling with intervention processes in the affected populations. Studies are currently being carried out in several indigenous populations of Argentina, Mexico and Venezuela [29]. In 2016, "The Clinical Rheumatology Journal" published a supplement with information about the Maya-Yucateco, Mixtec, Chontal and Rarámuri populations from Mexico; Warao, Kari'ña and Chaima from Venezuela; and Qom from Argentina [29]. The design of the studies, including samplings, case definition and methodology, was the same. The methodology was that proposed by COPCORD. Overall, low back pain, osteoarthritis (OA) and rheumatic regional pain syndromes (RPPS) were the most prevalent rheumatic diseases across all populations. Among the inflammatory rheumatic diseases, RA was the most prevalent, especially in the Qom community (2.4%) [22]. There were variations in the prevalence of certain diseases among different populations. The low back pain was more prevalent in the Qom community (19.8%) [22] and the OA in the Chontal community (32.1%) [24]. Variations were not related to the design of the study but to the characteristics of the populations and environmental factors, that is to say, heavy loads in Chontales versus Rarámuris or Maya-Yucateco in people not exposed to the same environment [20-23, 26, 27]. These results give information on working and socioeconomic conditions in these populations.
2. Synthesis and interpretation of qualitative studies: Few researches have been conducted based on social impacts associated with MSDs so far. Most outcome studies in occupational health have been focused on workers' compensation (WC), insurance payments, provision of medical services, return-to-work time and other direct insurance and employment-related measures [30]. Unfortunately, there has been little research studying the impact on the social and family environment of the workers affected, as well as the indirect economic consequences. These complex interactions create significant difficulties for researchers attempting to study the social consequences of MSDs.
The sociodemographic characteristics of affected individuals and groups such as age, gender, ethnicity, nationality, education and socioeconomic status can influence the social consequences of the injury. They could also influence the responses of employers, insurers and medical providers [30].
Studies suggest that work-related injuries have significant long-term physical, economic and psychological consequences, which were worse in those who had been out of work for longer periods of time [31].
Patients with more serious MSDs have higher rates of psychological problems, drug abuse, and marital difficulties and the quality of the affected worker's family relationships.
Contemporary studies suggest that significant disparities in the incidence of MSDs and deaths still exist among various racial and ethnic groups. For example, in California, workplace injuries were found to occur 32% more frequently among black workers than among whites, and the rate for Hispanics is 18% higher [32]. There is scattered evidence indicating that the social consequences of MSDs also fall most heavily on women, minorities, immigrants and other vulnerable populations [33,34].

Discussion
It is extremely important to study in-depth the closely related social and cultural aspects. Only traditional social variables have been studied that are only the tip of the iceberg. Multilevel analysis (e.g., individuals, social environment, health system, employers, type of work, insurance) should be incorporated for study between MSDs and vulnerable groups [35].
The constant migration of vulnerable groups to developed countries and precarious work must be taken into account in the analysis of MSDs.
The approach to this problem should be through the qualitative methods. These can serve to contextualize quantitative data providing means of cross-validation and what is termed by social scientists as triangulation, that is, the use of different approaches, by the conceptual, methodological or data collecting, to study the same problem in order to optimize the understanding of underlying mechanisms, work activity and environment, relationships, and solutions.
The incorporation of the COPCORD methodology should be of great help because it would assist the health system in the appropriate selection and application of resources, as well as the decision making in the system, demonstrating that the major worldwide problems of rheumatic complaints and disability are not just relevant to the elderly populations of developed countries, but also to the vulnerable populations living in poorer conditions [36].

Conclusion and recommendations
The burden of MSK disorders is likely to vary in different parts of the world. While modernization has bulldozed the Western world toward similar lifestyles, it has not yet transformed the cultural and traditional picture of Asia, Africa and several regions of South America. The disease health process is cultural and is influenced by socioeconomic factors. Many indigenous groups traditionally squat and/or sit cross-legged on the ground to enhance their daily activities [37,38]. Several MSDs can interfere causing immense suffering and frustration. Despite severe pain and disability, people do not easily give up this traditional and cultural lifestyle. It also coping to pain and disability, giving priority to work. This can also be seen in different vulnerable groups, where the quality and precariousness of work make individuals normalize pain and coping to it.
The recommendations are based on the literature discussed in this chapter. The assistance to this problem should be multidisciplinary, using both qualitative and quantitative methodology.
A priority is the promotion and prevention of such conditions in the most vulnerable population groups, living in precarious conditions and social inequality.