Effects of multiple risk factors on upper limb musculoskeletal disorders among workers in inner Brazil

1 Introduction

Work-related musculoskeletal disorders (WMSDs), which represent a public health problem, are characterized by local or generalized pain, a feeling of heaviness, or muscle fatigue. These injuries originate or are aggravated by work activities, and can affect passive structures (bones and joints) and active structures (muscles, tendons, ligaments, and peripheral nerves) [1, 2] due to excessive use of body parts without adequate recovery. It is known that the origin of WMSDs is multifactorial [3–5]. Further, they are influenced by the characteristics of the work environment and the way the work is performed [3]. WMSDs is associated with higher presenteeism and sick leave days [6] and opioid consumption approximately 10% of the time [7]. In Brazil, 67,559 cases were reported between 2007 and 2016 [8].

As a rule, biomechanical factors (physical demands or abduction of the arm), individual factors (age or body mass index [BMI]), or stress act directly on WMSDs, in the same way that organizational factors (automatic machine speed and different requirements for work according to market demand) and psychosocial factors (psychological demands, decision latitude and social support) act indirectly [9]. Meanwhile, the literature presents many other factors associated with WMSDs, which can only be correctly understood in light of the work conditions.

Biomechanical aspects such as maintaining static postures, repetitive movements, excessive load lifting, and using vibrating tools are associated with WMSDs [2, 10–12]. Psychosocial factors, such as low reward, low control at work, and motivation [10–13] have been better studied recently, as they contribute to an increase in muscle tension, perceived exertion, and stress [14, 15]. Other authors consider that psychosocial factors influence the adoption of awkward postures, contributing to the illness of the workers [16]. Further, gender, education, and physical activity are associated with WMSDs [12], particularly in developing countries [17].

Prolonged and diversified exposure to factors that contribute to the increase in occupational diseases is responsible for approximately 71% of injuries classified as work accidents, especially diseases of the musculoskeletal system, which correspond to 16% of the benefits granted to employees during the period of absence from work [18]. Such accidents entail budgetary costs to the Social Security of Brazil (PSB in Portuguese). Approximately 5.75% of the benefits issued in 2019 were destined for the payment of sickness benefits and accidental benefits resulting from work, with the PSB incurring a cost of approximately R$ 4 billion. Of this total, 25.72% was destined for Brazilian northeastern, the second region of the country with the highest number of requests based on the PSB Statistical Bulletin of 2019 [19].

In the first four-month period of 2020— the second follow-up to the Worker’s Health Goal in the National Health Plan 2020/2023 [20]— the state of Alagoas had the second-highest coefficient of incidence of diseases and injuries related to work in the country (a total of 245.8). The state of Bahia had one of the lowest coefficients in the country (80.8). Although both are in the northeast region and have similar economic and population data, the results show significant differences that can be justified by the organization of work in each state [21]. The official data on the incidence of occupational diseases are limited in scope as a study basis since they exclude workers not linked to the general social security [22], especially workers in the informal sector, who represent 41.40% of the employed population in Brazil [23].

The inner region of these states is characterized by climatic vulnerability, scarcity of water resources, and, in general, low soil fertility [24]. The evolution of the states’ work policies was mostly developed to solve the drought problem and boost the technological development of the inner northeastern region [25]. Even today, the sectors that stand out in the economy are linked to this aspect, including agribusiness, family farming, textile production, tourism, and industry for the state of Alagoas [24]. However, industry, agriculture, and services have greater participation in the state of Bahia. The state tends to follow the Brazilian economy cyclically [26] and contrasts with the state of Alagoas, which sticks to its main economic activity.

The commercialization of productive activity in these places led to an accumulation of income that directly interferes with labor relations and results in high labor turnover, low wages, precarious bonds, intense competition among workers, unhealthy working hours, and labor exploitation [21]. These work characteristics are still linked to illiterate or poorly educated workers living at risk and with a minimum basic social infrastructure [26]. The literature associated with the occupational health of inner northeastern workers is still scarce, especially when it comes to musculoskeletal diseases and their related factors.

Thus, to analyze the profiles of the workers and verify the information listed, this study aims to conduct a multifactorial assessment of sociodemographic variables and occupational risks and their relationship with symptoms of WMSDs in the wrists, elbows, and shoulders of Brazilian inner northeastern workers from the health, education, trade, and industrial sectors.

2 Material and methods

3 Results

The items in COPSOQ II, JCQ, and ERI showed α= 0.70, ωt = 0.77; α= 0.75, ωt = 0.80; and α= 0.75, ωt = 0.79, respectively, indicating good internal consistency and reliability of the data collected via the questionnaire, given that both parameters are greater than or equal to 0.70, with ωt > α [43] Bartlett’s sphericity test yielded χ² = 63.55 [p = 0.000], χ² =211.11 [p = 0.000], and χ² = 38.49 [p = 0.002]; and KMO = 0.73, 0.74, and 0.76, respectively, for the items of COPSOQ II, JCQ, and ERI. This indicates good adjustments of the data to EFA [44] items with F and h2 values less than 0.30 and 0.20, respectively, were excluded from the study (Table 1).

Table 2 summarizes the sociodemographic characteristics of the participants. In general, the sample was composed of women (72.38%), aged up to 45 years (72.14%), normal weight (51.67%), high school level (34.05%), married (52.38%), without children (69.05%), and who practiced physical activity (52.14%). As for the occupational group, the sample was heterogeneous in terms of gender, BMI, education, and children. In trade, health, and education, the sample mostly comprised women; in industry, the number of men was higher. Regarding BMI, education workers were predominantly of normal weight; in the other groups, the prevalence of overweight individuals was high. Concerning education, health and education professionals completed higher education. Meanwhile, in industry and trade, the individuals had high school level education. Most workers in industry and trade had children; this was not the case for education and health workers.

Table 3 presents the organizational data, and most workers were public servants (69.05%) who had no other job (71.43%), had worked for up to 15 years (58.33%), worked up to 40 hours a week (57.14%), and with more than 11 months between vacations (53.10%). All factors were heterogeneous within occupational groups. Most health and education workers were public servants. As for time with the company, many health and retail workers had been in the role for less than a year; while in education, many had been in the job for more than 16 years. Trade workers worked fewer hours a week, while industry workers worked more hours. Most industrial and commercial workers took vacations after 11 months of work, while a significant portion of health and education workers had taken vacations before 11 months of work. It is evident that a much larger number of workers in industry and commerce had no other jobs. Furthermore, education and trade workers had a more significant variation in performance activities.

Regarding biomechanical risk factors, Table 4 shows that most workers spent more than six hours in a standing position (62.38%) and using their hands and fingers (55.71%). Further, many of the individuals worked up to six hours a day sitting (59.05%), with the upper limbs (42.14%) and lower limbs (40.48%) in an uncomfortable position, with a curved spine (45.71%) and carrying 16 to 25 kg (45.71%). For up to one hour a day, these workers squat (87.14%), with a twisted spine (50.00%), carrying up to 6 kg (55.95%) or between 6 and 15 kg (79.05%), performing repetitive movements (37.38%), and using hand tools (88.10%). For most workers, effort (56.67%) and physical demands (52.14%) were low. However, heterogeneity was observed. A much larger number of health and industry workers work on their feet, and many industry workers sit for less than an hour. Additionally, a more significant proportion of industry workers endure for more than six hours with their upper and lower limbs in an uncomfortable position, as well as being bent or twisted, lifting loads between 6 to 25 Kg, performing repetitive movements, using fingers and hands, and making use of hand tools.

Table 5 presents information about psychosocial factors. Most workers perceive high significance (68.33%), commitment (56.90%) and control (53.81%), and job satisfaction (53.81%). Psychological demands (51.43%), support from co-workers (56.19%) and supervisors (52.38%), reward (51.19%), excessive commitment (50.71%), and motivation (58.10%) were also considered high. The perception of most workers was low for job insecurity (55.71%) and work–family conflict (52.86%). Heterogeneity was observed only for the factors meaning of work and control over the work. Health and education workers more easily perceive the meaning of their work for society and have greater autonomy and freedom of decision regarding job procedures.

Regarding the results for WMSDs, Table 6 shows that most responses were “no pain” for all regions assessed. However, a substantial number of workers had WMSD symptoms, with 20.00% and 21.67% of workers reporting mild symptoms in the left and right shoulders, respectively. Moderate symptoms were reported by more than 8.00% of workers in the elbows. Likewise, 9.29% of workers reported intense symptoms in the left wrist. The distribution of symptoms was si

Table 7 shows the results of the ordinal logistic regression model for the body parts. Although the distribution of symptoms in terms of their intensity is similar among the body’s dimensions for all the anatomical parts analyzed, they were not necessarily the same risk factors contributing to WMSD symptoms. Biomechanical factors such as the use of vibrating tools (for more than six hours a day), keeping the upper limbs in an uncomfortable position (between one and six hours a day), and psychosocial factors such as job satisfaction and work–family conflict had an impact on the likelihood of developing WMSD symptoms in both shoulders. Meanwhile, the (public) work environment and job insecurity increased the possibility of symptoms only in the right shoulder. Likewise, the age factor (older than 45 years) increased the likelihood of symptoms only in the left shoulder.

This phenomenon was repeated when analyzing the results of the models for the wrists and elbows. Factors such as the (public) work environment and the maintenance of superiors in an uncomfortable position increased the potential of symptoms only in the right wrist. Further, having another job reduced the likelihood of symptoms only in the left wrist. Factors such as age (greater than 45 years), working with the spine curved (between one and six hours a day), control over the work, and excessive impairment influence only on symptoms in the left elbow. Similar to the possibility of variation in work activities, the use of tools that vibrate the hands and the perception of physical demands had repercussions on symptoms only in the right elbow.

Different factors increased the likelihood of developing symptoms in both dimidia of the analyzed body parts. Biomechanical factors include the maintenance of the upper limbs in an uncomfortable position. The use of tools that vibrate the hands increased the probability of symptoms in the right and left shoulders by twice. The work environment (public) and the use of tools that vibrate in the hands increased the likelihood of symptoms in the right and left wrist by three and five times, respectively. Lifting loads (up to 6 kg) and the need to keep the lower limbs in an uncomfortable position increased the potential of symptoms in the left and right elbows by four and three times, respectively.

This study obtained evidence of the risk factors that influence upper limb work-related musculoskeletal disorders (in shoulders, wrists, and elbows) in the pre-selected workers in different sectors in the inner northeastern region of Brazil. The regions were specifically in the internal areas of the states of Bahia and Alagoas. This issue has great relevance because recognizing these factors benefits the academic research community and workers and employers, as well as helps formulate internal policies to improve working conditions [45]. To the best of our knowledge, this is the first study carried out in this specific population.

Another significant finding was that these factors could contribute to WMSD symptoms on both sides. Table 6 shows the similarity between the symptoms of both dimensions for the shoulders, wrist, and elbows. Nonetheless, the regression model results (Table 7) showed that some factors might have repercussions in symptoms in only one of the dimensions. Therefore, when considering symptoms only on the right side, for example, one can run the risk of ignoring that a factor can act in isolation on the left side. Such findings can be helpful in the development of policies focused on reducing WMSDs, as it presents more precisely the actual effect, right or indirect, of the risk factors on each side of the parts of the body.

The multifactorial role of risk factors in WMSDs on the shoulders, wrists, and elbows was also evidenced. Bovenzi et al. [46] stated that during the performance of activities with the upper limbs, such parts of the body (the shoulders, elbows, and wrists) work together as biomechanical links. Their study also defended the existence of multifactorial data, such as demographic, socioeconomic, biomechanical, physical, psychological/psychosocial, and organizational risk factors in the workplace, which can assist in developing WMSDs. However, others point out that these diseases are due to the sum of these risk factors, time of exposure [47], excessive use of the locomotor system, lack of time for recovery [8], repetitive and forced movements [48], and mental stress [49, 50]. Additionally, Leite et al. [47] reported that repetitive movements are dominant factors in developing these work pathologies, especially in monofunctional workers, so that the variation of activities tends to reduce the likelihood of WMSD.

Among the analyzed members, the shoulders received more indications of pain, with the education sector being the most affected by the symptoms. Further, there was a high incidence of discomfort in the wrists for this sector, almost equivalent to that of the shoulder. Cheng et al. [51] pointed out the existence of WMSD in workers in the education sector, with the shoulders and wrists being the most affected parts, with a WMSD prevalence of 63.4% (n = 246) and 56.7% (n = 220), respectively, in their studies. Likewise, Ng et al. [10] pointed out that relationships were found between psychosocial factors and musculoskeletal disorders, mainly among professionals in the education sector. Their research also showed that the most significant experience of WMSD among the participants was on the wrist (93.2%). Musculoskeletal and psychosocial problems increased during the COVID-19 pandemic due to online job [52], so studies on the relationship between musculoskeletal disorders and psychosocial factors will be increasingly necessary.

Biomechanical factors dramatically increased the potential of developing symptoms in the shoulders of workers. The use of manual vibrating tools for an extended period (more than six hours per day) had a two-fold increase in the likelihood of developing symptoms in the shoulders. The relationship between vibration and shoulder pain has already been observed among male workers [53]. For shorter periods, no risk was found for any of the shoulders. Similarly, the need to keep the upper limbs in an uncomfortable position for more than an hour a day proved to be a risk factor for the shoulders, increasing the likelihood of musculoskeletal symptoms by up to twice.

The use of tools that vibrate the hands contributed to the development of symptoms in all joints of the upper extremities. Similarly, Bovenzi et al. [46] pointed to a greater risk for workers with musculoskeletal disorders in the upper limbs exposed to vibrations transmitted by the hands, with the results being more significant for the occurrences in the elbow, forearm, and wrist or hand. Furthermore, in the same study, it was found that the increase in vibrations transmitted by the hand increased the probability of developing WMSDs. Exposure to vibration changes depending on the body part and the distance from the source, and its impact can also be dichotomous [47].

It was found that when using vibrating tools for a long time, there was a two-fold increase in the likelihood of symptoms occurring in the right wrist. Meanwhile, the potential becomes greater (five times) when analyzing the left wrist. This increase is believed to be related to the need for left-handed individuals to use tools idealized for right-handed people, especially in the health sector [54]. The absence of left-handed tools has already been demonstrated [55]. In the industrial sector, left-handers improvise on how to perform work because of inappropriate tools, which leads many workers to adopt new standards for carrying out labor operations, with current tools and machines not being readily adapted to the needs of these workers [56]. Such findings reinforce the need to build models for each dimidium of the body parts.

The age factor (> 45 years) increased the likelihood of symptoms of only the left shoulder by 60.00%. Recent findings by Bodin et al. [9] did not find that age > 45 years was a direct risk factor for shoulder WMSDs. However, the difference in realities experienced by inner northeastern Brazilian and French workers can explain the contrast in the results of the studies. Unlike the French, country workers mostly carry out their work activities under Fordist/Taylorist molds (a man, an activity, and a workplace) with tasks that are still extremely manual and with little technological solutions. While the work presented by Bodin et al. [9] did not clarify which shoulder was considered in the construction of the structural equation model, assuming that it was the right shoulder (usually selected, since most of the population is right-handed), there would be no difference with the findings of this study. Thus, the age factor (> 45 years) was only considered and identified as being at risk for shoulder symptoms because isolated models were built for the right and left sides. Meanwhile, review and meta-analysis papers indicated that older workers have a greater risk of shoulder WMSDs [31, 57]. Therefore, further studies should explore this relationship to clarify the relationship between age and shoulder symptoms.

Regarding psychosocial factors, there is evidence that musculoskeletal symptoms are lower when workers are extremely satisfied with their work [58, 59], indicating that psychological and social aspects influence WMSDs. Some studies have suggested that the influence of psychosocial factors is indirect, but still acts on the perception of stress [9]. Others associate psychosocial factors with adopting bad work postures [60] and inappropriate movements [16], leading to WMSDs. Among the psychosocial factors presented in the models, we highlighted the relationship between control and symptoms in the right shoulder (OR = 0.83), job satisfaction and symptoms in the left (OR = 0.79) and right (OR = 0.70) elbows, and satisfaction at work and symptoms in the left (OR = 0.86) and right (OR = 0.83) wrists. Therefore, psychosocial factors can also mitigate the occurrence of WMSDs. The findings of this research are in line with those of the studies by Eatough et al. [61] on self-control at work and shoulder symptoms, Silva et al. [41] on job dissatisfaction and symptoms in the elbows, and Veisi et al. [62] on dissatisfaction and wrist symptoms. Job satisfaction improves the performance and motivation among the staff [63], and should be improved in the workplace.

This study has several limitations. First, this was a cross-sectional study. Longitudinal data are known to be more reliable and accurate. Second, pain originating in other regions of the body was not considered to radiate to the parts included in the study; however, symptoms in the neck may reflect pain in the shoulders. The third limitation is associated with not using a structural equation model, which could indicate the factors that act directly and indirectly on pain symptoms. The fourth limitation is associated with the absence of data on hand dominance. The fifth limitation is comparisons between groups were compromised by the asymmetry between sample sizes from different occupational sectors. Future studies may verify interactions between risk factors and the development of WMSD symptoms, and should also contain a greater discussion of recent work in the area, emphasizing the importance of the proposed study. They could also analyze the relationship between hand dominance and the occurrence of WMSDs due to the use of inappropriate work tools in a symmetrical sample from different occupational sectors.

5 Conclusion

This study sheds light on the factors that contribute to upper extremity musculoskeletal symptoms in workers from the inner regions of the states of Alagoas and Bahia. The absence of previous studies on workers in this population makes it difficult to compare the results in different scenarios. A series of policies aimed at preserving the musculoskeletal condition of workers can utilize the findings of this study as a starting point.

It was reinforced that the origin of WMSDs is multifactorial, with sociodemographic, occupational, biomechanical, and psychosocial factors influencing the development of symptoms. Further, the importance of building models for body dimensions is evident. Age, for example, generated significant results only for the left shoulder and left elbow; however, the same relationship was not confirmed for the right shoulder and right elbow. Likewise, different risk factors have a more significant impact depending on the size of the analyzed body part. Therefore, prevention strategies for WMSDs, designed by local enterprises, must consider that each part of the body, whether on the right or left sides, has its own risk factors. By ignoring such phenomenon, risk factors can be wrongly disregarded in ergonomic and work safety interventions.