Evaluation of an 8 hour versus a 12 hour shift roster on employees at a power station

doi:10.1016/S0003-6870(99)00025-3

Applied Ergonomics

Volume 31, Issue 1, 4 January 2000, Pages 83-93

https://doi.org/10.1016/S0003-6870(99)00025-3 Get rights and content

Abstract

Several studies exist that have conducted research into the effects of different shiftwork patterns on the individual, especially regarding 8 and 12 h rosters. The findings of these studies have been largely supportive of longer shifts, however, the effects on work performance are not as clear cut. This study aimed to examine the changeover from an 8 h roster to a 12 h roster in a power station via monitoring on-shift performance, general health and well-being, sleep and mood behaviour, as well as absence and accident data. Results suggest that the domestic and social life of workers was markedly improved under the 12 h roster. Improvements in physical health, sleeping behaviour and mood state of employees were also documented. On-shift performance measures showed an increase in error rates at the end of a 12 h shift. Ways of reducing the risk of error towards the end of a 12 h shift should be explored. The results of this study suggest that 12 h shifts are a valid alternative to 8 h shifts in this particular workplace, although tasks that require error-free activities should not be performed towards the end of a 12 h shift.

Introduction

Shiftwork has often been considered to be detrimental to the health of workers and the ill effects of working shifts have been widely documented in the literature (Folkard and Monk, 1979; Singer, 1982; Rutenfranz et al., 1985; Colligan and Tepas, 1986; Bohle and Tilley, 1989; Akerstedt, 1990; Glazner, 1991; Siebenaler and McGovern, 1991; Aguirre and Foret, 1994; Paley and Tepas, 1994). Although, as Koller (1983) and Colligan and Rosa (1990) point out, there is also evidence that working shifts does not hold any great adverse effects on the well-being and health of some individuals, with a few individuals preferring shiftwork to other forms of work.

The ill effects of shiftwork include disruptions to circadian rhythms (Colligan and Tepas, 1986; Monk, 1990; Siebenaler and McGovern, 1991), gastrointestinal problems stemming from irregular diet and eating habits (Singer, 1982; Colligan and Tepas, 1986; Glazner, 1991), impairment in sleep quality and quantity as a result of daytime noise and environmental factors like light and heat (Monk, 1990; Glazner, 1991; Parkes, 1994) and restrictions on home and social life (Rowland, 1982; Smith, 1982; Walker, 1985; Monk, 1990).

Solutions are being sought to combat the adverse effects on the individual that have been associated with working shifts. One alternative to the traditional shiftwork pattern is the adoption of compressed work weeks. Compressed work weeks involve the use of a set block of shifts of increased length, compensated for by shortening the work week with three to four extra days rest.

It is generally accepted that compressed work weeks can be advantageous to the worker as they contain shorter blocks of shifts, fewer successive night shifts, increased blocks of free time and more weekends off. This increase in useable leisure time for the worker is an attractive alternative to the 8 h system. Conversely, 12 h shifts involve an additional 4 h in working time per shift with this increase in working time possibly leading to fatigue and the extended work hours may also unfavourably affect a worker's health.

Studies involving the comparison of 8 and 12 h rosters have been conducted in both laboratory and field work, with findings of these studies largely supportive of longer work shifts (Peacock et al., 1983; Frese and Semmer, 1986; Lees and Laundry, 1989; Williamson et al., 1994). However, the effects of the extra time on shift are not clear cut for work performance. Performance tasks in several studies have indicated improvements, or no change in performance (Peacock et al., 1983; Duchon et al., 1994), while in others decrements in performance have been observed (Volle et al., 1979; Daniel and Potasova, 1989; Rosa et al., 1989; Rosa, 1991; Rosa and Bonnet, 1993).

This study aimed to investigate the changeover from an 8 to a 12 h shift roster in a particular workplace through examining on-shift performance, general health and well-being, sleep and mood behaviour, as well as absence and accident data at the workplace. The results from this investigation of a `real-life’ situation were aimed to add to the growing body of literature concerning the evaluation of compressed work weeks in the workplace.

Section snippets

Subjects

Subjects were all employees who worked at an electrical power station and participated in working shifts. A total of 27 male employees participated in the study, with 15 employees participating in the data collection for the 8 h shifts and 12 employees participating during the 12 h shifts. The sample size for the study is small. However, this was the total number of shiftworkers employed at the power station at the time of the investigation. Employees were required to perform a variety of tasks

Biographical information

The general biographical information for the study sample is depicted in Table 1. The employees who worked the 8 h roster had equivalent characteristics in most demographic variables to the employees who worked the 12 h roster with no significant differences being found to exist on age, the number of hours worked per week, the percentage married, the number of hours partners worked in paid employment, the distance lived from the power station, nor on scores of job satisfaction. Twenty per cent of

Discussion

The adoption of a 12 h roster to replace an 8 h roster in this particular workplace produced improvements in several areas of importance for the individual.

Conclusion

The popularity of the compressed work week among employees and the improvements in the social and domestic situation, the health status, mood states and sleep quality and quantity in the present study all point to the serious consideration of 12 h shifts as a valid alternative to the previous 8 h roster in this workplace. However, the increase in error rate on the vigilance task at the end of a 12 h shift for infrequent stimuli suggests that the extra time on shift may hamper an employee's ability

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Evaluation of an 8 hour versus a 12 hour shift roster on employees at a power station

Abstract

Introduction

Section snippets

Subjects

Biographical information

Discussion

Conclusion

Int. J. Ind. Ergon.

Irregularity of working hours in railway workers and types of complaints

Int. Arch. Occup. Environ. Health

Psychological and psychophysiological effects of shift work

Scand. J. Work Environ. Health

The impact of night work on psychological well-being

Ergonomics

The stress of hours of work

Am. Ind. Hyg. Assoc. J.

Shiftwork effects on social and family life

Occup. Med.: State Art Rev.

Biological rhythms and performance

Oral temperature and performance in 8 h and 12 h shifts

Ergonomics

Extended workdays in an underground minea work performance analysis

Human Factors

The Information Processing and Performance Test Battery

Shiftwork and performance

Human Factors

Shiftwork, stress and psychosomatic complaintsa comparison between workers in different shiftwork schedules, non-shiftworkers, and former shiftworkers

Ergonomics

Shiftworkits effect on workers

Am. Assoc. Occup. Health Nurses

Acute and chronic effects of cigarette smoking on exhaled nitric oxide

Am. J. Resp. Crit. Care Med.