Volume 19, Issue 1 (2023)                   ioh 2023, 19(1): 393-407 | Back to browse issues page

XML Persian Abstract Print

Download citation:
BibTeX | RIS | EndNote | Medlars | ProCite | Reference Manager | RefWorks
Send citation to:

URL: http://ioh.iums.ac.ir/article-1-3325-en.html
Occupational Health Research Center, Department of Occupational Public Health, Iran University of Medical Sciences, Tehran, Iran , arp_63@yahoo.com
Abstract:   (945 Views)
INTRODUCTION: Sleep is one of the physiological necessities of the body that is effective in maintaining the balance of the body's biological activities and maintaining the normal function of memory and cognitive skills. Less than 7 hours of sleep may decrease the quality of people's performance. Shift working is one of the most common reasons for reduced sleep quality among workers, which can disturb the normal sleep cycle(1). Irregularities in the sleep-wake cycle also lead to increased fatigue and mental health problems by increasing the secretion of the hormone adrenaline into the bloodstream.
Shift working is work activities outside the usual timetable, which is especially common in social jobs. It is estimated that about 20% of the world's workforce is in the shift working group. The results of epidemiological studies showed that the incidence of adverse health consequences due to shift working is higher compared to day-working. Shift working can cause cardiovascular problems, gastrointestinal disorders, musculoskeletal disorders, fertility problems, increased risk of thyroid cancer, mood swings, and other health effects. The International Agency for Research on Cancer (IARC) also classifies shift working in Group A2 as "probably carcinogenic to humans"(2). Shift working is an effective factor for the rate of health problems. Prolonged shift working time increases the risk of disease and can increase the intention to leave and burnout at work.
The shift working as the most common pattern of working hours in the railway industry(3) has developed to increase the quality of life of metro passengers and thereby facilitate a more efficient transportation and movement of passengers in metropolitan areas. The transformation of intercity passenger transportation spaces from land-based to underground models has put the construction and operation of new metro lines as a subset of the railway industry on the government agenda. In this regard, Tehrans' municipality administrators have improved transportation conditions and increased metro lines in the urban development program. The increase in underground rail lines will be accompanied by an increase in the need for subway operators to attend unusual work hours. The results of recent studies demonstrated that subway operators have lower quality and sleep hours compared to other shift working jobs. On the other hand, the need for constant monitoring of the environment, information, and decision-making processes is estimated to be very high for metro drivers, which could cause mental and physical fatigue and reduced job satisfaction. In the present study, relying on the importance of providing and maintaining health and safety in the metro drivers, the effect of the shift working on sleepiness and the occurrence of health and mood effects in drivers of Tehran Urban & Suburban Railway Co was investigated.
METHODOLOGY: 363 Tehran metro drivers from lines 4, and 5 were selected by a census method and they were informed about the study and their consent were obtained in a special form. All study participants were divided into the control group (day workers) and case group (shift workers with fixed shifts of 9 or 12 hours). Their psychometric properties and sleep disorders were surveyed by the Survey of Shift workers (SOS) questionnaire(4) and Epworth Sleepiness Scale (ESS)(5) questionnaire, respectively. The validity of the SOS questionnaire was confirmed on 100 participants in the present study with a Cronbach's alpha coefficient of 0.72. The information about demographic characteristics of workers, shift working pattern, job satisfaction, mental and psychological disorders, health problems, sleep disorders, the effect of shift work on individual and social living conditions were obtained by SOS questionnaire. The ESS questionnaire with 8 questions and a scoring range of 0 to 3 examines the possibility of a person taking a shut-eye at work. In this questionnaire, the total scores obtained between 0-6, 7-10, 11-15, and 16-24 indicate adequate sleep, mild, severe, and dangerous sleepiness, respectively. The validity of the ESS questionnaire in the present study was equal to 0.93. The short-term physical effects of shift work in this study were also evaluated by an occupational physician during a clinical checkups and health problems related to shift working were recorded in the quarter before the study. In the medical checkup, questions related to digestive problems (anorexia, stomach pain, nausea, heartburn, indigestion, bloating, abdominal pain, and defecation disorders), cardiovascular problems (tachycardia, chest discomfort, dizziness, shortness of breath, high or low blood pressure, and arrhythmia), immune system problems (recurrent infectious diseases, long recovery period after illness), musculoskeletal disorders (shoulder and back pain, waist, arms, ankles, and knees) were asked. SPSS v.19 statistical software was used to analyze the data of the present study. Descriptive analysis and independent t-test were used at a significance level of 5% to express the frequency distribution and analyze the relationship between job factors and the effects of shift working.
RESULTS: All participants in the study were male with a mean age of 31.1 ± 4.5 years (the range of 21- 58 years) and a mean work experience of 6.2 ± 4.3 years ((the range of 1 - 12 years). The results of the statistical test showed that there were no statistically significant differences in age based on the mean age variable between shift working group (case) and day working groups (control) and also between the two shift working pattern (9 hours (6:00 to 15:00) or 12 hours (6:00 to 18:00)) (p-value> 0.05). The work experience in the 12-hour shift working group was statistically significantly higher than the 9-hour shift working group (p-value = 0.03) which, was not statistically different from the control group.
The results of clinical checkup showed that stomach pain (62.8%) and bloating (67.6%) were the main digestive problems in train drivers. The stomach pain in the case group was significantly higher than the control group and working time was identified as an effective factor for these consequences. Chest pain (56%), shortness of breath during activity (77.8%), pain in the shoulder/neck (84.6%), waist/back (85.7%), and leg/knee (81.9%) %) were the most common problems reported in train drivers, which showed a significant difference with the control group (p-value <0.05). The increase in shift work hours was associated with a significant increase in shortness of breath and chest pain, but this difference in the rate of complaints of musculoskeletal pain among different shift working pattern was not significant (p-value <0.05). Increased chances of recurrent infectious diseases in 78.5% and long recovery period were reported in 75.8% of the participants in the case group, which did not show a significant difference with the control group. Increasing the working time from 9 to 12 hours did not affect the incidence rate and length of the recovery period of infectious diseases (p-value <0.05).
Decreased quality of social life in the case group showed a statistically significant difference from the control group (p-value = 0.006). Most shift workers reported their work hours interfering with family life conditions and leisure activities. The effect of increasing shift work hours on the quality of social life was not significant (p-value <0.05). However, self-reports of the case population with shift durations of 9-12 hours compared with the control population, stating mood changes such as irritability, nervousness, and feelings of misery and guilt did not show a significant difference (p-value <0.05). Similarly, the results obtained from the self-reports of all the study participants (the case and control groups) did not show a statistically significant difference in the rate of fatigue and sleepiness during work in different shift working patterns (p-value <0.05). Comparing the job satisfaction of the case and control population using the SOS questionnaire demonstrated a statistically significant difference (p-value=0.006). The results also showed the optimum rate for the control group was 89.5%, while the corresponding rate was 59.3% for shift workers. And, increasing shift hours was effective statistically significant in reducing their job satisfaction (p value=0.016).
The effect of demographic characteristics of age and work experience on the incidence of musculoskeletal pain in the waist/back and arm /hand, recurrent infectious diseases and long recovery period, mood changes, job satisfaction, fatigue, and sleepiness in the two groups 9 and 12 hours shift workers were not statistically significant (p-value <0.05). Increased age and work experience were associated with an increase in the rate of stomach pain, chest pain and shortness of breath, decreased quality of sleep and social life, and increased pain in the shoulder/neck and leg/knee in the shift working groups (p-value <0.05).
DISCUSSION: Railway drivers typically have heavy workloads and mental loads, and often they are shift workers. Work time is often a major challenge for workers because it requires balancing between productivity and sleep time. Most shift activities lead to chronic sleep deprivation that leads to the discrepancy between rest times and working time, which leads to decreased efficiency, mood swings, and fatigue, and sleepiness. The results of the present study also showed that shift working patterns compared to day-working can be associated with negative effects on workplace awareness, social living conditions, job satisfaction, and health problems such as musculoskeletal pain, gastrointestinal and respiratory disorders. The increased duration of working hours from 9 to 12 hours showed an intensification shift work complications. The metro drivers of the Tehran Urban & Suburban Railway Company mainly complained of stomach and chest pain. Gastrointestinal disorders in shift workers are related to various factors such as diet disturbance, psychosocial stress, lack of sleep, and also disturbance of the body's circadian rhythm, which can lead to stomach pain by reducing acidity and gastric emptying. Walton et al. also reported chest pain, palpitations, headaches, guilt, and shame from acute stress in metro drivers that were improved by changing shift working patterns(6).
The higher rate of musculoskeletal disorders in shift workers compared to the control group in the present study can be due to several reasons. Some researchers believe that the presence of vibration in the cabin of train drivers, unsuitable postures during activity, and working stress are the main causes of musculoskeletal pain in metro drivers. Vitamin D deficiency in jobs with closed environments and away from natural sunlight is another factor that may increase the risk of musculoskeletal, mental, and autoimmune disorders. In other studies, increasing age has been introduced as an effective factor for the prevalence of physical symptoms in shift workers, which was contrary to the results of this study. The reason for this discrepancy can be related to the low distribution of age variables in this study population. Because most of the participants were in the young age group.
The results of the present study showed that the rate of infectious diseases and longer recovery period in shift workers is higher than the control group, which could be related to disruption of the sleep-wake cycle in shift workers. The results of scientific research show that stress and anxiety, especially irregular sleep-wake cycles, can lead to higher rates of viral infectious diseases such as colds and longer recovery periods. Lack of sleep in the body can cause changes in the secretion of inflammatory cytokines and inadequate expression of the immune gene, activation of the sympathetic and hypothalamic-pituitary-adrenal pathways, and an increase in the secretion of the hormone cortisol. The abnormal secretion of the hormone causes stress and disruption of the immune system, which increases the risk of viral diseases.
Mood changes and quality of social life in the present study did not show significant differences between the shift workers and the control group. However, the complaints' rate in the shift workers was higher than in the control group. Hege et al. showed that shift workers as transit drivers could cause conflict between work and life and increase family and social problems compared to other workers(7). Déme et al. also believe that the need for sleep and rest during the daily activities of their family members could be the reasons for the conflict between work and life in shift workers(8). Mood disorders due to lack of sleep also were recognized in most studies as one of the most common complaints in shift workers, which is associated with increased levels of anxiety and depression.
In the present study, sleepiness in the shift workers and control group did not show a significant difference, which could be related to the nature of the work of metro drivers and rapid changes in the work environment. However, studies by the American Academy of Sleep Medicine (AASM) showed that sleep deprivation is related to negative health effects and identified shift workers as a vulnerable population. The sleep pattern in the shift workers often exposes them more to unwanted sound and inappropriate lighting and reduces their quality of sleep, which in many cases causes chronic insomnia in shift workers. Some researchers have pointed to sleeplessness in shift workers compared to day workers and believe this can cause depression and job dissatisfaction. Sleep deprivation and chronic fatigue could lead to negative effects on job performance and social functions of individuals having increased mood swings. Numerous factors such as light and heat in the train cabin, an inadequate pattern of work/rest, and lack of sleep at night can affect the aggravation of fatigue and sleepiness in metro drivers. Although Hu and Lodewijks pointed out in their study the occurrence of fatigue is not necessarily associated with sleeplessness but, it may play a role in the negative consequences of shift working and exhibit increased dissatisfaction and reduced quality of life.
The decrease in job satisfaction in shift workers in the present study was consistent with many scientific studies in this field. Wei et al. identified shift work patterns and long working hours as a cause of work-life conflict in train drivers and could affect the status of their job satisfaction. The results of this study also showed that increasing the duration of shift work of metro drivers can be a deterministic factor for the consequences of working patterns. On the other hand, an increase in shift work duration increased their fatigue rate. Johnston et al. showed that fatigue increased slightly during the first 4 hours of the shift but doubled at the end of working time with 12 hours. Work-related fatigue is a natural human response that can occur due to limited physical/mental energy resources and can change their level of attention and motivation. Hülsheger also believes that the fatigue pattern, especially in people with sleep deprivation, follows a quadratic equation that leads to increased fatigue and will lead to a wide range of chronic diseases.
CONCLUSION: The present study demonstrated that the shift work patterns in the Tehran urban and suburban railway drivers could cause sleepiness and increase the incidence of health disorders. And, such phenomenon was intensified by increasing the working time from 9 hours to 12 hours. The need to increase the awareness of metro drivers for improving passenger safety is one of the goals that should be taken into account in planning the work pattern system. Hence some modifications in management control measures are needed for improving working conditions and satisfaction of metro drivers. Further studies for identifying the impact of demographic and environmental characteristics on the health effects of shift workers could be beneficial for their working conditions.
Article number: 26
Full-Text [PDF 526 kb]   (298 Downloads)    
Type of Study: Research | Subject: Organizational Psychology
Received: 2021/11/30 | Accepted: 2022/09/12 | Published: 2023/04/8

Add your comments about this article : Your username or Email:

Send email to the article author

Rights and permissions
Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

© 2024 CC BY-NC 4.0 | Iran Occupational Health

Designed & Developed by : Yektaweb