Study of Fatigue Changes during the Working Day on the Base of Job Stress: The Role of Job Demands and Job Control on Fatigue Occurring

In recent decades, the essence of work was changed because of the great evolutions in several parts of manufacturing and industry. Increasing global competitive marketing was a cause of these changes. Generally, changes in work include: mechanization, automation, information technology, organizational restructuring, work-related modification and staff multitasking. According to these changes, the need to learn and develop new skills led to increased psychosocial factors including job stressors. Almost, the majority of people experience job stressors at work. Job stress occurs when there is no balance between job demands and worker’s capabilities. In several studies, job stress is identified as an important and effective factor that effects on health, performance and industrial safety. Usually, workers exposed to several stressors in the workplace, including: relationships and tensions among employees, high workload, long work hours, poor job design, role ambiguity or conflict, weak support from management and coworkers, high-speed work and so on. Job demands like workload, physical factors of the workplace and job control manner are the most effective stressors on the workerschr('39') life. Fatigue is a significant negative consequence of these stressors. For example, high job demands lead to impaired cognitive functioning and tired feeling that those are the fatigue symptoms. As regards the fewer studies about stress among industrial workers in Iran and there is no study on the relationship between job stressors and fatigue among Iranian workers, this survey was performed to study relationships among job stressors, especially job demands and job control, with fatigue; also, assessing the fatigue changes during the working day according to the job stressors was the other aim of this study.

This survey was a cross-sectional study that gathered from three hundred and thirty-eight industrial workers from the big industries of Tabriz city. The purpose of the study was explained with clarity to all participants. Only those who agreed to participate in the study and who had more than one-year working experience, healthy people (Who didn’t suffer from diabetes, asthma, blood pressure and anemia) and those who worked in day shift, were enrolled. Participants were selected by a convenient method for this study. A valid job stress HSE questionnaire, a demographic factors questionnaire and fatigue checklist were used to conduct data. At first, to study and evaluate of fatigue in time, a designed checklist was used. According to the aim of this study, we designed a checklist that measures worker’s acute fatigue in every time of working day. By this checklist, the participants rated their fatigue in the range of 0-10 (0= there is no fatigue feeling, 10=there is an excessive fatigue feeling), at specified hours during the working day from 7:00 to 18:00. Then, the demographic questionnaire and fourteen items of job stress questionnaire to evaluate job demands and job control were provided to participants. The scoring of job stress questionnaire was ranked from 0 to 4 (no to more) in this study. To data analyses, the working day was divided into three times, time 1 was from 7:00 to 10:00 (7:00, 8:00, 9:00 and 10:00), time 2 was from 11:00 to 14:00 (11:00, 12:00, 13:00 and 14:00) and time 3 was from 15:00 to 18:00 (15:00, 16:00, 17:00 and 18:00). Then, the average of fatigue was computed for each time. The variables of job demands and job control were adjusted between two groups (little and more) at the start of the study. The normality of quantitative data was evaluated by K-S test, identity of the covariance matrix was checked by Mauchlychr('39')s W test and the Nested Repeated Measure and Controlling Covariates test was used to investigate fatigue among three time periods by SPSS Software Version 25. At the end, the Controlling Covariate test was used by Minitab Software Version 18.1 to control of confounding variables. The results include three P-values for comparing groups between three times. The first was P-value (Group) for comparing between three groups, the second was P-value (Time) for comparing between three times (time 1, time 2, and time 3), and the third P-value (Level) was computed for comparing fatigue in each depression levels. The level of significance was set at P-value < 0.05. All results were expressed as Mean ± SEM (standard error of the mean).

According to the results, the mean age of workers was 37.04±0.4 years; and the mean working experience of workers was 11.45 ± 0.35 years. Also, the majority of the participants were male workers. About 52 percent of workers had more than 11 years of work experience and 62 percent of participants were fixed shift workers. The workers worked on average 203.65±1.8 hours in month. They had a mean 30.57±1.4 minutes rest-time in a day. Fifty and three percent of workers believed that they had a moderate income while the others were dissatisfied with their income, and they considered it inadequate. Results showed that job demands variable was significantly related to fatigue in time (p<0.001) and fatigue was increased by increasing of job demands (p<0.001). According to the results, by increasing job demands level from low to high, the severity of fatigue has increased. Also, the significant relationship between job control and fatigue was showed in results (p<0.001). According to the results, by decreasing job control level from high to low, the severity of fatigue has increased (p<0.001). At the end, the mean of fatigue had a positive trend from the start of working day and was increased by spending of time; fatigue score was increased by changing time from time 1 to time 2 and from time 1 to time 3 (p<0.001).  

The job stressors, especially job demands and job control, have adverse effects on several aspects of human life; fatigue is one of these negative consequences. According to the results, fatigue is a gradual process that increases by spending time from the starting of job activities. If so, the level of job control is low, or the job demands are higher than the capacity of workers in an organization, the severity of fatigue will increase. The importance of these findings is in the planning and implementation of necessary actions to reduce fatigue and its related incidents. So, it is recommended that industry managers and relevant authorities take proceedings to reduce the effects and severity of fatigue by reducing the time pressure, work speed, and workload and increasing the power of decision-making and application of work skills. Organizations also can reduce fatigue by decreasing the long hours of work and dedicating enough time for the rest of the workers.