Abstract
BACKGROUND:
The automotive industry is labor-intensive, and workers are involved in highly repetitive tasks, long hours, and medium to low workloads, resulting in work-related musculoskeletal disorders (WMSDs), which have become a major health concern for workers in this industry. China is a major automotive country with tens of thousands of auto repair workers, but their conditions of WMSDs have been poorly reported.
OBJECTIVE:
This work aimed to analyze the current prevalence of WMSDs and their associated risk factors among automobile maintenance workers.
METHODS:
A total of 539 respondents from 50 automotive repair and maintenance companies in China were selected to investigate the prevalence of WMSDs via the modified Nordic Musculoskeletal Disorders Questionnaire. Chi-square test and logistic regression models were applied to analyze their associated risk factors.
RESULTS:
The total prevalence of WMSDs among 539 workers was 32.8%. The top three body parts for prevalence were the lower back (17.1%), neck (16.3%), and shoulders (14.5%). The highest prevalence of WMSDs was found in the neck (23.6%) and lower back (14.3%) for sheet metal workers and mechanics, respectively, whereas painters had the highest prevalence of WMSDs in the lower back and feet (both at 15.4%). Logistic regression analysis showed that females were at higher risk of WMSDs than males (OR 5.027, [95% CI] [1.278–19.772], p < 0.05). Workers subjected to uncomfortable positions were at increased risk of WMSDs (OR 1.79, [95% CI] [1.333–2.410], p < 0.01).
CONCLUSION:
The prevalence of WMSDs is high among automotive maintenance workers, with the highest prevalence in the lower back (17.1%). Uncomfortable working postures and frequent repetitive movements with lower limbs and ankles at work may be important risk factors.
Introduction
Work-related musculoskeletal disorders (WMSDs) are a series of health issues regarding the locomotor system such as muscles, tendons, bones, cartilage, ligaments, and nerves caused by occupational activities. WMSDs involve all forms of health disease states from minor, transient injuries to irreversible, function-restricted injuries [1]. WMSDs can cause inefficiency at work and seriously affect workers’ health [2], resulting in varying degrees of economic burden and health loss [3, 4]. These disorders have a serious impact on the health of billions of occupational groups around the world [4] and have become a major occupational health problem worldwide [5]. Their negative impact on population health and social economy is worrisome. However, in China, WMSDs have not received sufficient attention; statutory occupational diseases do not include WMSDs in China, but their prevalence is as high as 28.5%–76.9% [6].
Work conditions, nature of work, and posture at work are major factors in the occurrence of WMSDs [7]. WMSDs are associated with a variety of occupational factors, including heavy physical work, heavy lifting, static work, poor work posture, repetitive handling, mechanical vibration, and other poor ergonomic factors [8]. The incidence and location of WMSDs vary by industry or job type. For example, studies have shown that hospital nursing staff and long-term computer users are most likely to develop musculoskeletal symptoms in lower back, neck, and shoulders [9, 10]. WMSDs in batik workers are mainly found in the shoulders, lower back, and ankles [11].
With the improvement of people’s living standards, the automobile has become an essential means of travel available to the most families in China. The automobile sales and service industry show booming growth. WMSDs have become a serious occupational health problem caused by adverse ergonomic factors such as forced body posture, repetitive work, and physical labor, which are widely present in automobile maintenance operations [12, 13]. As a result of the labor-intensive nature of the automotive maintenance industry, as well as the high load, repetitive tasks, and forced working positions, high levels of WMSDs often arise in the neck, shoulders, lower back, and wrists of workers [14]. WMSDs pose a huge burden on workers’ health and social medical expenditure [15]. Thus, ways to prevent and reduce the occurrence of WMSDs are imperative. However, relevant studies on WMSDs in this population are rare. Therefore, the occurrence status of WMSDs and related adverse ergonomic factors in the working population must be investigated to provide scientific basis for the prevention and reduction of WMSDs.
Materials and methods
Participants
In this study, a total of 539 workers from 50 automotive repair and maintenance companies in Beijing, Chongqing, and Tianjin were selected for the survey via cluster sampling method. The types of work included machinist, painter, and sheet metal workers. The inclusion criteria were as follows: workers with ≥1 year of service on the job. The exclusion criteria were as follows: non-WMSD patients with congenital spinal deformity, trauma, infectious diseases, and malignancies. A total of 539 workers participated in the study. All participants were asked to complete the electronic questionnaire independently. The study was reviewed and approved by the ethics committee, and the electronic informed consent form was signed by the participants prior to the survey. This study was reviewed and approved by the Medical Ethical Review Committee of the National Institute for Occupational Health and Poison Control, Chinese Center for Disease Control and Prevention on December 16, 2021 (No. NIOHP202122). The selection process of survey respondents is shown in Fig. 1.
Participant inclusion of work-related musculoskeletal disorders among automotive repair workers from Beijing, Chongqing, and Tianjin, China, 2019.
The improved electronic Nordic standardized musculoskeletal symptom questionnaire (NMQ) [16] referring to the Dutch Musculoskeletal Questionnaire used was provided by National Institute of Occupational Health and Poison Control of China Center for Disease Control and Prevention. Basic demographic information of workers, exposure to adverse ergonomic factors, and occurrence and regions of musculoskeletal diseases were collected to conduct a cross-sectional study of occupational epidemiology. The occurrence of WMSDs and occupational relevance were then analyzed. The contents of the questionnaire were as follows: (i) demographic data: gender, age, height, weight, BMI, dominant hand, education, marital status, monthly income, physical exercise, and smoking; (ii) factors related to occupational activities and symptom occurrence: work type, service year, working posture and duration, working time, and working shifts; and (iii) regions of symptom occurrence: the pain condition of nine regions was investigated, including neck, shoulders, upper back, lower back, elbow, hands, legs, knee, and foot. All participants agreed to the content and signed the electronic questionnaire.
The judgment criteria of WMSDs: WMSDs were defined as symptoms such as discomfort, pain, numbness, or activity restriction that occurred in the musculoskeletal system for at least 24 h in the past 12 months without relief after rest [17]. Total prevalence of WMSDs = sum of the number of people with WMSDs in at least one body part / total number of respondents×100.0%.
Quality control
The survey was conducted through unified training for surveyors before the investigation to ensure uniform standards and methods. The survey was conducted in the form of 1: N. One investigator conducted a face-to-face survey on N respondents. The respondents scanned the QR code of the electronic questionnaire and answered the questions online. After submission, the questionnaires were directly uploaded to the cloud database.
Statistical analysis
We adopted the statistical software SPSS version 24.0 for sorting and analysis. Measurement data were described by mean and standard deviation (x±s). Chi square test was used to compare the prevalence in each region, followed by single-factor analysis of possible risk factors. The variables with differences in univariate analysis were analyzed by using the bivariate logistic regression model. The statistical significance level was defined as p < 0.05 in the statistical test results.
Results
Participant characteristics
The 539 respondents included 251 (46.6%) machinists, 165 (30.6%) sheet metal workers, and 123 (22.8%) painters. The respondents comprised 524 males (97.2%) and 15 females (2.8%). The respondents were 32.0±7.8 years old. Table 1 shows the characteristics of the 539 participants.
Demographic characteristics of work-related musculoskeletal disorders among automotive repair workers from Beijing, Chongqing, and Tianjin, China, 2019 (N = 539)
Demographic characteristics of work-related musculoskeletal disorders among automotive repair workers from Beijing, Chongqing, and Tianjin, China, 2019 (N = 539)
NOTE. BMI: Body Mass Index.
The total prevalence of WMSDs was 32.8% in 539 respondents. The prevalence in different body parts was 5%–17.1%, with the highest in the lower back (17.1%) and the lowest in the elbow (5.0%) (see Fig. 2).
Prevalence of work-related musculoskeletal disorders in various body regions among automotive repair wokers from Beijing, Chongqing, and Tianjin, China, 2019.
The prevalence of WMSDs differed in body regions for different job types. The top regions for WMSDs in sheet metal workers, machinists, and painters were the neck (23.6%), lower back (14.3%), and lower back and feet (both 15.4%), respectively (see Table 2 and Fig. 3).
Prevalence of work-related musculoskeletal disorders by body part for different types among automotive repair workers from Beijing, Chongqing, and Tianjin, China, 2019, n(%)
Prevalence of work-related musculoskeletal disorders by body part for different types among automotive repair workers from Beijing, Chongqing, and Tianjin, China, 2019, n(%)
Prevalence of work-related musculoskeletal disorders by region for different job types among automotive repair workers from Beijing, Chongqing, and Tianjin, China, 2019.
Univariate analysis
The chi-square test was applied to conduct a one-way analysis of the demographic characteristic factors, job types and work organization factors, and job posture factors in relation to the total prevalence of WMSDs in the study population (see Tables 3–5).
Univariate analysis of different demographic characteristics of work-related musculoskeletal disorders among automotive repair workers from Beijing, Chongqing, and Tianjin, China, 2019
Univariate analysis of different demographic characteristics of work-related musculoskeletal disorders among automotive repair workers from Beijing, Chongqing, and Tianjin, China, 2019
Univariate analysis of different types of operations of work-related musculoskeletal disorders among automotive repair workers from Beijing, Chongqing, and Tianjin, China, 2019 (N = 539)
Univariate analysis of different operational postures of work-related musculoskeletal disorders among automotive repair workers from Beijing, Chongqing, and Tianjin, China, 2019
Multi-factor logistic regression analysis was conducted using the presence or absence of WMSDs as the dependent variable and factors that were statistically significant in the univariate analysis as independent variables. Thus, 23 independent variables were included. Gender, marital status, working in a squatting or kneeling position for long periods of time, working in an uncomfortable position, having two co-workers taking shifts, and performing the same movement of the lower limbs and ankles repeatedly while working were factors influencing the development of WMSDs in automotive maintenance workers (see Table 6 and Fig. 4).
Multifactor analysis of risk factors for musculoskeletal disorders among automotive repair workers from Beijing, Chongqing, and Tianjin, China, 2019
Multifactor analysis of risk factors for musculoskeletal disorders among automotive repair workers from Beijing, Chongqing, and Tianjin, China, 2019
Logistic regression analysis of risk factors for WMSDs among automotive maintenance workers.
As the world’s largest automotive market [18], the WMSDs of automotive manufacturing and maintenance industry workers in China must not be ignored. This study investigated the prevalence of WMSDs and their associated risk factors among workers in 50 automotive repair and maintenance industries in China. Results showed that workers in this industry were at risk of developing WMSDs, with an overall prevalence of 32.8% (177/539). The region with the highest prevalence was the lower back (17.1%). The prevalence of WMSDs varied by body region among workers in different job types. The highest prevalence was found among sheet metal workers in the neck (23.6%), machinists in the lower back (14.3%), and painters in the lower back and feet (both 15.4%). Work factors such as working in uncomfortable positions and working with the same movement of the lower limbs and ankles repeatedly at work were risk factors for the development of WMSDs. These findings might provide some insights into the situation of prevalence of WMSDs in the industry. WMSDs are of increasing concern as an influential factor in the physical health of occupational populations. Studies on WMSDs have been conducted on occupational groups such as hospital workers [19], dentists [20], footwear workers [21], and office workers [22], but few studies have been conducted on the prevalence of WMSDs among workers in the automotive repair and maintenance industry. In this study, 539 workers from 50 automotive repair and maintenance companies in China were selected as respondents to study the prevalence of WMSDs and their associated risk factors. This study provided some practical relevance to improve understanding of WMSDs in this industry.
The automotive repair and maintenance industry covers a wide range of work types, including sheet metal workers, machinists, and painters. Thus, workers are exposed to a wide range of occupational ergonomics factors and are at high risk of developing WMSDs due to the wide range and intensity of their work. A previous study reported that the lower back and neck have the highest burden of musculoskeletal disorders in most countries of Eastern Mediterranean Regions [23], and similar results were obtained in this study. The findings of this study revealed that the overall prevalence of WMSDs in the 539 study participants was 32.8%. The prevalence of WMSDs was highest in the lower back (17.1%), second in the neck (16.3%), and third in the shoulder (14.5%). However, this result differed from the highest prevalence of WMSDs in the neck, shoulder, and ankle among automotive assembly workers [13]. This difference may be related to the fact that automotive maintenance workers and automotive assembly workers do not have exactly the same load during their operations. Moreover, the study population differed in terms of age, working age, lifestyle, and other factors. The highest prevalence of WMSDs in the lower back was consistent with the findings of Mulugeta [24] and Hossain et al. [25] in their studies of auto repair workers. A report of WMSDs on dentists’ neck and shoulder revealed a correlation between neck bending and damage during work [26]. Unsurprisingly, the neck was also found to be the second part with the highest prevalence of WMSDs in this study.
The occurrence of WMSDs is associated with a number of factors. Factors such as repetitive work tasks in occupational activities, prolonged passive body posture, and vibratory work increase the risk of WMSDs [27]. When more than one of these factors are present together, the risk of WMSDs increases. Individual worker characteristic is a factor in the development of WMSDs. The differences in the occurrence of WMSDs between men and women were observed in assembly workers, utility workers, or workers in construction, maintenance, and repair work [28]. Overall, females have a higher risk of developing WMSDs than males [29]. For example, one study indicated that the risk of WMSDs is higher among female than male bank workers (p < 0.05) [30], possibly due to differences between males and females in human physiological functions, body height measurements, and differences in workload [31]. This study also found a significantly higher prevalence of WMSDs in females than in males, but this may also be due to the fact that the automotive maintenance companies are predominantly a heavy manual industry with a predominantly male worker composition and a smaller number of females, with a significantly higher prevalence of WMSDs than males. The results of this study suggested that marital status was an influencing factor for suffering from WMSDs among automotive maintenance workers, and our results showed that marriage was a protective factor for workers to suffer from WMSDs, which may be related to marriage’s positive impact on the mental health of workers [32]. Nevertheless, the mechanisms by which marriage affects the occurrence of WMSD are unclear.
The results of this study demonstrated that working in an uncomfortable position and performing the same movement frequently and repeatedly on the lower limbs and ankles at work were risk factors for the occurrence of WMSDs, with OR and 95% CI of 1.792 (1.333–2.410) and 2.301 (1.334–3.971), respectively. Workers often need to remain in a passive and uncomfortable position to meet the vehicle’s construction to be close to the part of the vehicle that needs to be repaired during maintenance. There is a link between low back pain and the need to maintain a non-neutral trunk position such as bending or twisting the body when working under or on the sides of a vehicle [33]. In addition, automotive maintenance workers often work with their lower limbs and ankles repeatedly performing the same action, such as walking repeatedly and stepping on maintenance equipment repeatedly. Repetitive movements have been found to increase the risk of WMSDs in workers [34]. The high frequency of repetitive movements leaves the worker with insufficient time for muscle contraction to recover between movements, which is a factor in the occurrence of pain [35]. Long periods of squatting or kneeling and the fact that work is done by two workers in shifts proved to be protective factors for the occurrence of WMSDs, with OR and 95% CI of 0.663 (0.509–0.864) and 0.646 (0.423–0.985), respectively. This may be related to the standing or forced body position during the work of vehicle maintenance operations. Squatting and kneeling reduce the body’s center of gravity, easing the load and relieving muscle fatigue and pain caused by prolonged standing or sitting work. The body is susceptible to the development or exacerbation of WMSDs during prolonged sustained low load or brief strong load shocks [36]. The prolonged squatting/kneeling posture acts as a cushion to correct and improve long-term working postures, which suggests that employers should improve poor posture [37] in terms of setting up workstations, equipment, and tools that fit the body size and working style of the workers. However, prolonged squatting or kneeling could lead to impaired blood circulation in local tissues, resulting in muscle strain, but this result may also be due to the age and lifestyle of the population investigated. The work was performed by two workers in shifts, so the work load on one individual was shared equally by two people, which reduced their load. In addition, shift completion allowed for muscle recovery between worker’s breaks, and another study reported that no work breaks are a significant risk factor for the development of WMSDs in occupational workers [30]. Alghadir et al. indicated that workers who take breaks during work report fewer WMSDs than their counterparts[38].
Strengths
This study provided an in-depth analysis of the prevalence and risk factors of WMSDs among workers in 50 automotive repair and maintenance companies in China, based on three dimensions (i.e., demographic characteristics, type of work and work organization, and work posture) and helped fill a gap in the current research on WMSDs in this industry. The study is valuable for understanding the prevalence and risk factors of WMSDs in this industry, as well as for preventing the development of WMSDs from an ergonomic perspective.
Limitations
The limitation of this study was that the data were drawn from 50 automotive repair and maintenance companies in China and might not fully represent the true picture of the prevalence of WMSDs in the Chinese automotive repair and maintenance companies. Data were collected by electronic questionnaires, and there might be some subjective bias in the respondents filling in the questionnaire entries, resulting in low actual data.
Conclusion
WMSDs were a significant contributor to health hazards in the occupational population. The results of this study suggested that automotive maintenance workers were at risk of developing WMSDs. In this study, the total prevalence of WMSDs among automotive maintenance workers was 32.8%. Risk factors for the disorders were predominantly working in uncomfortable positions and performing the same movement of the lower limbs and ankles repeatedly at work. Other adverse ergonomic factors were still not negligible. Notably, short breaks between work could reduce the risk of lower back pain [39]. Therefore, company managers should consider developing a reasonable shift system, increasing the cooperation of workers, creating a good working environment for workers as far as possible, and educating workers on the proper use of tools. Workers should be more aware of health protection and consider muscle stretching and recovery to effectively decrease the risk of WMSDs.
Ethics approval and consent to participate
The study was reviewed and approved by the Medical Ethical Review Committee of the National Institute for Occupational Health and Poison Control, Chinese Center for Disease Control and Prevention on December 16, 2021 (No. NIOHP202122). The respondents were informed about the study and their participation was voluntary and confidential. All participants provided written informed consent prior to enrollment. All protocols were performed in line with the Declaration of Helsinki.
Footnotes
Acknowledgments
The authors sincerely thank all participants from Chongqing, Beijing and Tianjin Municipal Centers for Disease Prevention and Control that were involved in this study.
Conflict of interest
The authors report no conflict of interest.
Funding
The study was funded by the Project of Occupational Health Risk Assessment and National Occupational Health Standard Formulation of the National Institute of Occupational Health and Poison Control (Project no. 131031109000160004).