Split-shift work in relation to stress,health and psychosocial work factors among bus drivers

1 Introduction

Shift work is associated with poor health, disturbed sleep, fatigue and lower satisfaction with working hours [1, 2]. The design of the shift system plays a key role for the problems associated with shift work [3]. For example, shift systems that include several consecutive long work shifts, insufficient rest time between work shifts and many consecutive work days are reported to be associated with more sleep/wake problems, poorer health and reduced well-being [4, 5]. However, there are some components of shift systems that have received little research attention. The present study examined one particular work schedule, namely split shifts, and the association with stress, health and satisfaction with work hours.

Within flexible shift work, split shifts are a common component for some occupations, for example transport, health care and the hospitality sector [6]. A recent report showed that 3.3% of all employees in Sweden worked a split shift at least once a month [7]. A similar rate has been reported in a EU study [8]. There is currently no consensus on how to define a split shift, but it is normally regarded as a long (>10 hours) work shift that is divided into at least two parts with an unpaid, or lower paid, break of 4-5 hours between the parts. A special case of split-shift work exists in maritime and certain long-distance transport, where employees often have more than one work shift per day and sleep and rest at or near the workplace [9]. However, the focus of the present study was on bus drivers in urban transport, a group that frequently works split shifts [10]. The urban bus industry is known for its peaks in traffic, with typically one travel peak in the morning and one in the afternoon caused by people commuting to and from work. This peak-type pattern demands more drivers during the morning and afternoon, partly explaining the frequent occurrence of split shifts.

The effects of working split shifts in bus transport are largely unknown, but there is good reason to believe that they may be associated with elevated stress, which in turn may cause disturbed sleep and fatigue. Firstly, split shifts usually mean a long working day spent at the workplace, which may interfere with social life and cause poorer work-life balance and elevated fatigue levels. Secondly, split shifts often involve working during rush hours with traffic-related stress peaks, which causes a lot of disturbances such as difficulties meeting timetables, an unpredictable work situation and an increased risk of missing breaks (due to late arrival at the terminus). Thirdly, split shifts are undesirable to many workers and associated with low work time control, since it is not possible to influence (i.e. exert job control) split-shift days. Low work time control increases the risk of high work strain (defined as a combination of high work demands and low decision latitude), which is a well-known cause of psychosocial work stress [11]. Altogether, this may lead to chronic stress, which in turn increases the risk of low job satisfaction, poor health, disturbed sleep and excessivefatigue.

However, even though split shifts increase the risk of stress, how the drivers cope with the working hours is likely to play a key role for the consequences [10]. Some drivers may enjoy the flexibility offered by split shifts, using some of the spare time available in the middle of the day to recover (nap or rest), exercise or take care of pets. For others who cannot use the time between the shifts in a meaningful way, split shifts can cause a mismatch between individual needs and the work situation, since the individual is forced to adapt their life to the demands of working hours. Consequently, it can be hypothesized that individuals who do not feel in control when working split shifts, i.e. perceive it as a major problem, are more likely to experience symptoms of high stress levels and job dissatisfaction than individuals who do not experience such problems. Other factors such as health and social situation could also possibly be affected.

The overall goal with the present study was to explore the association between split-shift work among bus drivers and job satisfaction, stress, work-life balance and health, including sleep and fatigue complaints. The starting hypothesis was that drivers who perceive working split shifts as a problem report lower job satisfaction, poorer health, higher stress, poorer work-life balance and more sleep and fatigue problems.

2 Method

3 Results

In total, 232 (response rate 65%) bus drivers answered the questionnaire. The respondents mainly consisted of men working full time, with an average work experience of just over 13 years. A majority worked split shifts, of which around one-third indicated problems with this. See Table 1 for background factors.

4 Discussion

This study showed that a majority (64%) of bus drivers who worked split shifts did not perceive this working pattern as problematic. Thus, for the entire study group (n = 235) split-shift working was not significantly associated with job satisfaction, work-life balance, stress, health or fatigue complaints. There was a weak tendency (p≤0.08) for drivers working split shifts to report poorer sleep quality and lower satisfaction with their working hours, but these trends should be interpreted with great caution. However, there was a relatively large (36%) group of drivers who perceived split-shift working as a major problem. Among those drivers, several negative effects of split-shift working were found, such as poorer self-rated health, higher stress, more sleep and fatigue problems, lower satisfaction with work and working hours, and poorer work-life balance.

These results suggest that there is a large individual component in tolerance to split shifts, a finding which was expected and in line with the starting hypothesis. It is known from previous research that there are pronounced individual differences in how shift work affects sleep, fatigue, subjective health and well-being [15, 16]. Individual differences in tolerance to specific shifts are not well understood and previous research has mainly examined the influence of age, gender, personality traits and differences relating to circadian rhythm [16]. In the present sample, the latter factors are not likely to have a major impact on why some drivers have trouble tolerating split-shift working. Instead, one of the most obvious explanatory factor is how the drivers cope with the long rest time between the two work periods. If the drivers can use this break for something meaningful, such as napping, exercising or some social activity, and if the long working day does not disturb social and family life, then split-shift work may not be any more stressful or any worse than regular shift work. However, if the long break means just waiting for the next work period, possibly even anticipating severe fatigue or stress, or if the split shift work interferes with social life in a negative way, the consequences are likely to be negative.

The question about employees’ work time control showed that 81% of the drivers who disliked split shifts reported difficulties in influencing their working hours. The corresponding figure for the drivers who had no problems with split shifts was 42%. The group difference was even higher as regards the number of drivers who felt they could not control working time and viewed this as a major problem (71%, compared with 23% for the drivers who did not dislike split shifts). Low employee work time control has in previous research been associated with poor sleep and well-being, poor work-life balance and poor health [17–19]. Thus, the fact that the drivers who disliked split shifts experienced lower work time control is another possible reason why they reported more problems with stress and well-being, and poorer self-rated health.

As previously mentioned, there are very few in-depth studies of split shifts in relation to stress, sleep and health, although it is well known that such work hours are not desirable among bus drivers [10]. One of the few studies that is partly applicable to city bus drivers investigated job-related injuries and showed that split shifts did not have a higher accident risk than regular day shifts [20]. It has also been shown that split shifts are associated with long weekly hours of work [21]. A Swedish representative study found that 27% of the shift workers who had split shifts regarded this as a major problem [7], a lower proportion than in the present study (36%). On the other hand, split shifts in the representative Swedish study were not associated with subjective health, sleep and fatigue problems when other working time characteristics such as night work, early morning work and short rest between shifts were taken into account [7]. The lack of information on this issue suggests that more research, using longitudinal design, is needed before it is possible to conclude whether split shifts result in poorer health, sleep and fatigue problems, and poorer work-life balance.

The present study has several limitations. First, it is uncertain whether the results can be generalised to other occupations that have split shifts. Second, the cross-sectional design did not permit any conclusions to be drawn about causality. It is theoretically possible that stress, poor health and adverse psychosocial work factors, made it more difficult to manage split-shifts. Third, the study did not obtain information on how the drivers used the time during the break, in particular if they prioritised recovery activities such as napping. Fourth, it is difficult to obtain precise measures of working time exposure with questionnaire data. Future studies should preferably use objective working time data and examine whether there is a dose-response relationship between working split shifts and consequences related to sleep, health and well-being. Furthermore, the effects of split shifts should be investigated using objectively measured markers of stress, sleep and fatigue problems, preferably in an experimental field study. Finally, there is a need for future research to increase in-depth understanding of how people perceive working split shifts, by using some qualitative methodological approach (e.g. an interview study).

The study results have implications for scheduling of city bus drivers. A little more than one-third of the drivers in this study considered working split shifts to be a major problem and it would be desirable if drivers with this attitude could avoid such shifts. However, a potential negative consequence of removing split shifts entirely is that the number of very short (<5-6 hours) or very long (>10 hours) shifts could increase. Increased frequency of very long shifts may result in excessive fatigue and higher accident risks [22]. Increased frequency of short shifts may result in more undesired part-time work, or many consecutive workdays if working full time, which may lead to worse work-life balance. Thus, it is a great challenge to design good schedules that eliminate split shifts. An additional or alternative strategy is to improve the break conditions, for example provide good opportunities for sleep and exercise at the workplace, with the goal of making split shifts more attractive for the drivers.

5 Conclusion

The present study demonstrated that, in general, working shift schedules including split shifts did not seem to increase stress, affect job satisfaction or result in poorer well-being. However, drivers who perceived working split shifts as a major problem reported poorer health, higher perceived stress, interference of working hours with social and family life, lower sleep quality, more persistent fatigue and lower general work satisfaction compared with those who did not perceive split shifts to be a problem. Furthermore, drivers who reported problems with split shifts also perceived that their possibilities to influence working hours was lower, suggesting that they had lower work time control. In the long run, lower work time control can result in chronic stress and increase the risk of poor health. It is therefore recommended that drivers’ working time preferences be taken into account when planning shift schedules.

Conflict of interest

The authors have no conflict of interest to report.