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Fatigue Management

Literature review of Comparisons between 12 and 8 hour shifts (11th Feb 2005)

Authored by Caroline Fisher

In recent decades, an increased need has developed for many organisations to operate their workplaces continuously over a 24-hour period, due to the nature of the work, technological developments, economic pressures and an increased demand for 24-hour services (Bendak, 2003). However, shift workers who work traditional shift rotations (consisting of six or seven straight shifts, with one full weekend off every four to six weeks) often display perturbed performance, increased or more serious accid ents, lowered production, higher absenteeism, health problems, familial problems, low morale, and job dissatisfaction when they work nights and rotating shifts (Duchon, Keran & Smith, 1994). The problems faced my individual shift workers are both complex and multi-faceted, and unlike most occupational stressors, can impinge on the whole of their lives (Folkard, 1993). A conceptual model of the manner in which these problem areas relate to the features of shift systems, and to one another, is shown in At tachment A. In an attempt to address the needs of shift workers and of the organisation, prolonged and continuous work schedules are becoming increasingly commonplace in many work settings. An example of this type of schedule is the "compressed work week", where shift duration is typically lengthened from eight hours to 12 hours; resulting in fewer actual work days and more consecutive days off (Purnell, Feyer & Herbison, 2002).
There is a wealth of literature comparing the advantages between 8 hour and 12-hour shifts. However, the research findings are largely equivocal and inconsistent with both advantages and disadvantages of working an extended shift (Smith, Folkard, Tucker & Macdonald, 1998). For example, in a review of the existing research on shiftwork, Bendak (2003) found that of the 49 studies that compared 12 hour shifts with eight hour shifts, some studies found negative effects attributable to 12 hour shif ts, others found positive effects, some found mixed results and some found no differences between the two work durations. These inconsistencies appeared to be irrespective of the type of work being studied, yet related to the differences between studies in assessment measures, shift design factors and uncontrolled differences in levels of work demands and associated workload. Positive evaluations of the implementation of a 12 hour shift system also appeared to be related to the degree of choice an individua l had in whether they were required to work the 12 hour shift (Smith, Folkard, Tucker and Macdonald, 1998).
Conversion to a compressed working week is often considered because of the perceived potential benefits for production and morale, reduction of sickness absence, and the convenience of having extra time off work (Smith, Folkard, Tucker & Macdonald, 1998). It appears that combining a compressed and a shift schedule may mitigate some of the negative effects frequently associated with shift work and capitalise on some of the positive effects associated with compression (Pierce & Dunham, 1992) . In practice, having more time off work provides more uninterrupted time for recovery, family, leisure and other social activities; which in turn, increases job satisfaction (Johnson & Sharit, 2001), and reduces absenteeism (Duchon, Keran & Smith, 1994; Latack & Foster, 1985). Research conducted by Peacock and associates (1983) found that measures of physical fitness, blood pressure, sleep duration, sleep quality and subjective level of alertness all showed improvements when a 12-hour system wa s adopted in the workplace. Furthermore, Duchon and colleagues (1994) found that survey responses indicated positive effects of the 12-hour schedule on morale, health problems, stress, eating habits, family life and sleep quantity and quality. Twelve-hour shifts are also popular as they reduce the frequency of trips made to and from work (Smith, Folkard, Tucker & Macdonald, 1998). These extended shifts also seem to conserve energy and reduce traffic congestion, particularly since some of the journeys ar e made outside of peak times (Kogi, 1991).
There have also been disadvantages attributed to the 12-hour shift work system. The extra four hours worked by employees on 12 hour shifts may increase levels of fatigue and cause disruption to circadian rhythms (Rosekind et al, 1995 in Purnell, Feyer & Herbison, 2002). This may contribute to a general deterioration in employees' immediate and long-term health (Macdonald & Bendak, 2000). Twelve-hour night shifts are of particular concern due to excessive fatigue induced from a long shift a nd high workloads when combined with low alertness levels due to lower endogenous arousal at night (Bendak, 2003). Research has also shown that performance levels considerably drop in the last four hours of a shift, a decrease that is especially prominent on 12-hour shifts. This can be of real concern especially when the job being worked is highly monotonous and sedentary, such as monitoring computer screens (Smith, Folkard, Tucker & Macdonald, 1998). The possible increase in fatigue levels due to exten ding work duration by 4 hours may lead to more errors at work (Baker, Olson & Morisseau, 1994), which in turn may have negative effects on productivity and work quality (Williamson, Gower & Clarke, 1994).
Fatigue generated by working a 12 hour shift may also make an individual more susceptible to accidents (Williamson & Feyer, 2000), severe sleepiness, safety problems, weight gain, greater stress states (Ognianova, Dalbokova & Stanchev, 1998), lower morale, lower productivity and economic loss (Bendak, 2003), especially when 12-hour shifts are combined with high workload levels (Macdonald & Bendak, 2000). These factors take on particular importance in industries where public health and safety are concerned (Mitler et al, 1998 in Purnell, Feyer & Herbison, 2002). Additionally, sleep-deprived night workers driving home in the early hours of the morning are at an increased risk of falling asleep at the wheel (Horne & Reyner, 1999). This is because a 12-hour shift does not usually equate with only being active for 12 hours. There can be a considerable extension of the person's time awake on either side of the shift as a result of factors such as a long journey (Smith, Folkard, Tucker and Macdonald, 1998). If the commute exceeds three hours, time available to sleep is reduced to six hours, which is insufficient rest for most adults (Gould, 1989). Theoretically, there is extra recovery time available after the 12 hour shifts have been completed; however it is not clear from the research as to whether this extra time is enough to recover from the extra fatigue induced during the consecutive 12 hour shifts due to the extra 4 hours worked each time (Bendak, 2003). Anderson and Bremer (1987) found that employees who attempted to compensate for sleep loss by sleeping longer than 10 hours on their days off reported greater sleepiness on the job than employees who slept fewer than 10 hours. The extra recovery time may also lead to increased moonlighting (Smith, Folkard, Tucker & Macdonald, 1998). The 12 hour shift also provides less time for other activities during the work week, thus this type of schedule may cause difficulty to some individuals, for example: in managing home duties, childcar e activities, family and social life (Tepas, 1985 in Smith, Hammond, Macdonald & Folkard, 1998). Days off can become boring if a partner works and spending may increase during longer rest breaks. It is possible that spouses may not like the 12-hour schedule, even when the shift worker strongly favours it (Smith, Folkard, Tucker and Macdonald, 1998).
However, Harmer and colleagues (2002) state that longer shift durations may not necessarily cause decrements in human performance through induced fatigue if managed properly. Proper management may occur through moderating workload levels and sensibly allocating and distributing rest breaks to allow temporary recovery, and by sensibly scheduling the shift system to allow a complete recovery (Duchon, Keran & Smith, 1994; Bendak, 2003). For example, a short duration nap of 20 minutes taken in the workplace may counteract performance deficits associated with the first night shift (Purnell, Feyer & Herbison, 2002). Periodic assignment of mentally challenging or light physical tasks may also lessen possible fatigue among 12-hour night shift workers (Duchon, Keran & Smith, 1994). Furthermore, rosters should be made to cover overtime without holding a 12-hour shift worker or calling in a worker who has had fewer than three days off after working four 12-hour shifts. A minimum of three days off i s necessary after four 12-hour shifts to alleviate fatigue, as excessive fatigue has been found to develop when employees worked four consecutive 12-hour shifts with only two days off between shifts (Gould, 1989).
The consequences of possible human errors should be taken into consideration when deciding on the length of the shift system. It may not be advisable to introduce 12-hour shifts where some errors would have dire consequences (Rosa, 1995 in Bendak, 2003). Various researchers have also concluded that 12-hour workdays are not appropriate, especially at night, for work that includes high physical or mental loads (Kogi, 1991). Unfortunately, however, there has been no research to suggest the levels of workload a cceptable for 12-hour shifts (Bendak, 2003). It is advisable that the organisation takes into consideration the individual's day to day home activities as well as family commitments and social life when deciding on shift duration. Research emphasises, though, that it is flexibility and the opportunity to have some control of working time, that appear to be the significant factors in the way a 12 hour shift system impacts upon the individual (Latack & Foster, 1985; Smith, Hammond, Macdonald & Folkard , 1998). In light of the uncertainties and contradictions in the research on the use of extended workdays in workplaces, it is reasonable to suggest that employees on extended workday schedules be re-evaluated at periodic intervals. One approach may be to use a short questionnaire to elicit employees responses about their schedule, coupled with monitoring of company records pertaining to absenteeism, safety and productivity (Duchon, Keran & Smith, 1994).

 

 

 

References
Anderson, R.M., & Bremer, D.A. (1987). Sleep duration at home and sleepiness on the job in rotating twelve-hour shift workers. Human Factors, 29, 477-481.
Baker, K., Olson, J., & Morisseau, D. (1994). Work practices, fatigue, and nuclear power plant safety performance. Human Factors, 36, 244-257.
Bendak, S. (2003). 12-h workdays: current knowledge and future directions. Work & Stress, 4, 321-336.
Duchon, J.C., Keran, C.M., & Smith, T.J. (1994). Extended workdays in an underground mine: A work performance analysis. Human Factors, 36, 258-268.
Folkard, S. (1993). Editorial. Ergonomics, 36, 1-2.
Gould, S. (1989). Safety considerations related to 12-hour shift schedules. Nuclear Safety, 30, 103-105.
Harmer, M., Sallinen, M., Ranta, R., Mutanen, P., & Muller, K. (2002). The effect of an irregular shift system on sleepiness at work in train drivers and railway traffic controllers. Journal of Sleep Research, 11, 141-151.
Horne, J., & Reyner, L. (1999). Vehicle accidents related to sleep: a review. Occupational Environmental Medicine, 56, 289-294.
Johnson, M.D., & Sharit, J. (2001). Impact of a change from an 8-h to a 12-h shift schedule on workers and occupational injury rates. International Journal of Industrial Ergonomics, 27, 303-319.
Kogi, K. (1991). Job content and working time: the scope for joint change. Ergonomics, 34, 757-773.
Latack, J.C., & Foster, L.W. (1985). Implementation of compressed work schedules: participation and job redesign as critical factors for employee acceptance. Personnel Psychology, 38, 75-92.
Macdonald, W. & Bendak, S. (2000). Effects of workload level and 8- versus 12-h workday duration on test battery performance. International Journal of Industrial Ergonomics, 26, 399-416.
Ognianova, V.M., Dalbokova, D.L., & Stanchev, V. (1998). Stress states, alertness and individual differences under 12-hour shiftwork. International Journal of Industrial Economics, 21, 283-291.
Peacock, B., Glube, R., Miller, M., & Clune, P. (1983). Police officers' responses to 8 and 12 hour shift systems. Ergonomics, 26, 479-493.
Pierce, J.L., & Dunham, R.B. (1992). The 12-hour work day: A 48-hour, eight-day week. Academy of Management Journal, 35, 1086-1098.
Purnell, M.T., Feyer, A.-M., & Herbison, G.P. (2002). The impact of a nap opportunity during the night shift on the performance and alertness of 12-h shift workers. Journal of Sleep Research, 11, 219-227.
Smith, L., Folkard, S., Tucker, P., & Macdonald, I. (1998). Work shift duration: a review comparing eight hour and 12 hour shift systems. Occupational Environmental Medicine, 55, 217-229.
Smith, L., Hammond, T., Macdonald, I., & Folkard, S. (1998). 12-h shifts are popular but are they a solution? International Journal of Industrial Economics, 21, 323-331.
Williamson, A.M., & Feyer, A.M. (2000). Moderate sleep deprivation produces impairments in cognitive and motor performance equivalent to legally prescribed levels of alcohol intoxication. Occupational Environmental Medicine, 57, 649-655.
Williamson, A.M., Gower, C.G.I., Clarke, B.C. (1994). Changing the hours of shiftwork: a comparison of 8- and 12-hour shift rosters in a group of computer operators. Ergonomics, 37, 287-298.

 

Attachment A

Figure A1. A conceptual model of the manner in which the various problems associated with shift work relate to both one another, and to the features of the shift system (Folkard, 1993).