Subjective measures of work-related fatigue in automobile factory employees

1 Introduction

Fatigue is an essentially subjective experience, and it is typically defined as extreme and persistent weariness, weakness, or mental or physical exhaustion [1, 2]. Work-related fatigue is related to occupational health. It can have serious maladaptive effects on the health of the working population. It can even cause chronic disease. Most individuals report feeling fatigued during work hours, especially after poor sleep or inadequate rest, after physical exertion, or after pronounced mental effort [3].

Work-related fatigue is considered a cause of occupational injury in most industrialized countries. Within the European community, 40% of workers are reported to experience significant fatigue [4, 5]. Similar cases have been reported from Norway [6], Canada [7], the United States [8], Sweden [9], and Japan [10, 11]. Work-related fatigue can affect occupational health and safety, personal well-being, and even national and personal productivity.

With the boom of industrial automation in China, automated equipment has been widely introduced in the manufacturing industry, especially in automobile factories. The amount of manual work has been decreased, and the jobs remaining for people are mostly monotonous and repetitive and commonly involve low workload. They may include monitoring the running of equipment, data entry, and assembly line work. It is well documented that monotonous and repetitive work can increase bodily pain (such as that of the lower back, shoulder, or neck) and mental weariness [12–15]. Aronsson et al. found the prevalence of neck and shoulder symptoms to be twice as high among workers involved in monotonous data entry work than among programmers and system operators [16]. Finally the symptoms could develop into physical or psychological disease, such as musculoskeletal disorders and chronic fatigue syndrome (CFS) [17]. Work-related fatigue is considered a common problem in the general population. It has been reported that about 142–560 persons per 1,000,000 adults in the United States experience prolonged fatigue, and the prevalence is higher among non-white persons [18]. In Japan, 60% of working people say they had felt “extreme fatigue” [19]. In China, more than 700,000,000 people have impaired health, with chronic fatigue as one of the main symptoms [20]. However, work-related fatigue is easy to overlook in automobile factories, because the tasks usually involve low workload. When people finally recognize their health problems after long-term fatigue, it maybe that its cumulative effect on health has already become serious and irreversible.

As the wellbeing of employees is of crucial interest to organizations [21], the specific fatigue status of the employees and the factors that induce fatigue should be studied. There are many factors that influence work-related fatigue, such as sleep debt, psychological distress, health perception, work conditions, personal characteristics and so on [22–25]. It was reported that people doing different jobs might have different feelings of fatigue even in same workplace [26], and people with different gender also performed differently [27]. Therefore, in our study, we compared the data from different job categories (engineers and workers) and gender.

Muscular fatigue is a common phenomenon for physical activities at work [28], therefore, repetitive work is usually defined by physical work characteristics, for example, upper extremity movements. Work-related fatigue caused by repetitive work usually straightforward attributed to mechanical tissue overload related to repetitive movements, force requirements, and awkward postures, but it is inherently correlated with psychosocial factors [29]. Psychological scales may offer a valid way to assess fatigue and its factors. This study, therefore, was to use subjective measures to assess work-related fatigue among automobile factory employees. A new working condition questionnaire was developed to assess work-related factors.

2 Methods

The survey was conducted among the employees of an automobile factory, and a package of questionnaires was handed out to measure different aspects associating with fatigue.

3 Results

At present, repetitiveness and monotonous work are common in industries with automated work processes [47]. Especially in China, working in an automobile factory has become repetitive and monotonous for employees since the development of industrial automation. People more easily experience fatigue, both physical and mental [48]. However, because of low workload, detriment to health attributable to prolonged fatigue cannot be easily assessed.

The results of this survey of the employees of a Chinese automobile factory showed that although about half reported themselves to be in very good health, the majority had felt fatigue frequently in the past one or two months. Both engineers and workers had problems with fatigue, which was significantly correlated with work-related factors, especially the factors related to the working environment and monotony. The significance of the relationship between self-reported health condition and fatigue confirmed that people could ascertain their own physical condition exactly from their subjective feeling of their own bodies, which meant that the subjective measures for their fatigue status were effective and believable, and some authors have reported, “If the person tells you that he is loaded and effortful, then he is loaded and effortful whatever the behavioral and performances measures may show” [49]. In this study, engineers had better quality of sleep and greater satisfaction with the working conditions than workers did. Both of the scores of PSQI in engineers and workers were higher than the average score in healthy adults [42]. The mean score of engineers was closer to the previously documented in subjects without shift work disorder, while the mean score of workers was closer to the score in subjects with shift workdisorder [50].

The fatigue experienced by engineers was less affected by the length of the work day. This was probably because most of the engineers had more regular shift work- schedules and rest arrangements. They could balance work and rest on their own. However, the workers’ schedules were mostly arranged according to the production order.

The scores of fatigue between men and women did not show significant differences, but they did differ significantly between engineers and workers. The FACIT-F score was 42.6 (SD = 6.4) for engineers and 35.6 (SD = 6.3) for workers. Both these figures were worse than in the general population in the U.S., for which the score was 43.6 (SD = 9.4) [51]. The workers reported more fatigue than engineers.

The indexes for predicting prolonged fatigue showed general fatigue to be more likely to emerge regularly and frequently over a long period for engineers than for workers. However, the physical fatigue of workers usually had a long duration. In this way, workers may be more likely to experience musculoskeletal disorders, and the engineers were more likely to develop multi-diseases syndrome, such as chronic fatigue syndrome.

In contrast to the predictions made here, the self-reported health problems of engineers were related to physical fatigue, but for workers they came mainly from mental fatigue. This is probably because doing the same job for a long time caused the employees to become skilled, then they would complete the tasks by a more effective method. That is, the workers could more easily deal with fatigue from physical work, and the engineers could easily deal with fatigue from mental work. The result was that people would be easily fatigued by tasks with which they were not familiar. Among work-related factors, working environments and monotony were more likely to induce general fatigue in engineers than in workers. Among workers, monotony was more likely to induce physical fatigue, working environment was more likely induce mental fatigue, and length of the work day was more likely to induce general fatigue. In this way, the improvement of working environment and monotony might help alleviate fatigue in both engineers and workers. The combination of appropriate work day and break schedules would be more effective in alleviating workers’ fatigue.

The results of this study need to be viewed with regard to several limitations. First, the work-related fatigue is prevalent in repetitive industrial work [48], in this study we only surveyed the fatigue and fatigue-related factors among engineers and workers in an automobile factory, further investigations should be conducted among more samples from different industries. Second, although we selected some fatigue-related factors, they were not insufficient, more influential factors should be considered in further research, for instance, shift work, which is highly associated with work-related fatigue [52, 53].

5 Conclusion

The prevalence of work-related fatigue was high among participating employees from this automobile factory, and workers felt more fatigue than engineers. The fatigue observed here was significantly correlated with work-related factors, especially working environment and monotony. For workers, length of the work day also significantly affected their fatigue. Some improvements in work-related factors in this automobile factory should be considered. Prolonged fatigue status in the employees might also induce occupational disease, such as musculoskeletal disorders and chronic fatigue syndrome. To assess people’s working conditions, WCQ, a new questionnaire, was developed and tested here. It showed acceptable reliability and validity. Results also showed fatigue to be more severe when people performed tasks with which they were not familiar, so some targeted training might help prevent fatigue.

Conflict of interest

The authors declare that they have no conflicts of interest. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee. Informed consent was obtained from all individual participants included in the study.