The Working Hours Act (Arbeitszeitgesetz, ArbZG) does not precisely define the term shift work. However, shift work is generally understood as work “in which work tasks are performed at varying times of the day or night or at constant, but ‘unusual’ working times – that is deviating from what is known as day work” (S2k Guideline (S2k-Leitlinie)). Work is often organised in such a way that employees can work consecutively at the same workplace, allowing for an extension of operating hours beyond the individual working times of the employees (Beermann, 2005).

Although shift work is an atypical form of working time, many jobs and sectors are inconceivable without night and shift work. Whether it is to ensure the provision of services to society (e.g. in hospitals or by the police) or for technological or economic reasons (e.g. at production facilities or in many service jobs), shift work is relatively widespread. An estimated one-sixth of employees in Germany work in shifts.

Employees who work nights and shifts have routines that conflict with both their circadian rhythms (the body’s "internal clock") and the rhythms of a society in which social life takes place mostly at the evening and on weekends. This can lead to health risks and impairments to social and family life, as numerous scientific studies have shown.

The design of shift schedules plays a central role in minimising the health and social risks associated with night and shift work. The Working Hours Act (Section 6(1)) consequently stipulates that the working hours of employees engaged in night and shift work must be set in accordance with “established ergonomic findings” on human-centred work design. The following recommendations for action provide guidance on how to organise night work and shift work in health-friendly ways.

Recommendations for action concerning the organisation of healthy night and shift work

The following recommendations for action can be formulated based on ergonomic findings:

1. The number of consecutive night shifts should be kept as low as possible.

• Although many shift workers who do five or more consecutive night shifts often perceive that their bodies adapt to night work, there is no real adaption of physiological functions to night work. Ergonomic studies have revealed that adaptation is only partial and is subsequently reversed during days off. Night work continues to be a challenge to the body's internal clock. Consequently, it is recommended that blocks of night shifts be kept as short as possible.
• Employees on permanent night shifts (who exclusively work at night) often have the impression that their bodies adjust to night work. However, the bodies of individuals with these working time patterns only truly adjust if they organise their free time to follow the same rhythm.
• Short blocks of night shifts help prevent the accumulation of sleep deprivation because the daytime sleep individuals get when working at night is usually of reduced duration and quality.
• In addition to this physiological issue, this recommendation is also relevant to shift workers' social and family lives. Traditional, slowly rotating shift systems (weekly rotation from early to late, and then night shifts) often result in workers not having a night off for two consecutive weeks (one week of late shifts followed by one week of night shifts). Rapid rotation, by contrast, allows at least one night off per week.

2. A block of night shifts should be followed by as long a rest period as possible, which should never be less than twenty-four hours.

• This recommendation is based on the finding that night work is particularly demanding, and employees must be given sufficient time to recover afterwards.
• An ideal rest period after a block of night shifts would be forty-eight hours. However, a long rest period after a block of night shifts often reduces the amount of uninterrupted time off, for example at weekends. This issue is particularly relevant for shift schedules with short blocks of night shifts.

3. Blocks of time off at the weekend are better than single days off at the weekend.

• Blocks of time off at the weekend provide employees with two consecutive free days, ideally including either Saturday or Sunday. For example, they may take off Friday and Saturday, Saturday and Sunday, or Sunday and Monday. This arrangement is preferrable because social and leisure activities usually take place at weekends. For instance, children do not usually attend school at weekends and many social occasions, such as sporting events, take place mainly then. The utility and leisure value of free time are significantly higher at weekends than on weekdays.

4. If possible, shift workers should have more days off during the year than daytime workers.

• Even where production lines operate continuously round the clock, weekends or public holidays on which employees work should be compensated for with time off in lieu. Furthermore, compensation must be provided for the additional strain caused by night shifts (Section 6(5) ArbZG). If possible, this compensation should take the form of time off. Depending on the number of night shifts worked, several additional days off should be granted.

5. Unfavourable sequences of shifts should be avoided: always rotate forward.

• Ergonomic studies have shown that forward rotating systems (early, late, then night shifts in sequence) result in fewer overall complaints from employees than backward rotating systems (night, late, then early shifts in sequence).
• Backward rotating systems are to be viewed particularly critically because they shorten the rest period between shifts. For example, if the late shift ends at 10 p.m. and the early shift starts at 6 a.m., there is only an eight-hour rest period, from which commuting time has to be deducted.
• However, problems often arise when changing from a backward rotating system to a forward rotating system because the blocks of time off at the weekend are shortened. In backward rotating systems, it is possible to end the early shift on Friday at 2 p.m. and start the night shift on Monday at 10 p.m., giving employees a long weekend. In forward rotating systems, however, the longest possible period of free time would only last until the late shift on Monday at 2 p.m.

6. The early shift should not start too early.

• The reason for this recommendation is to prevent the early shift from becoming a hidden night shift. In particular, employees with long commuting times would otherwise have to interrupt their sleep very early. This should be viewed critically, especially against the background of studies showing that shift workers do not usually go to bed earlier in the evening, even if they start their early shift very early. This leads to significant sleep deprivation and excessive fatigue, which can result in additional strain and an increased risk of accidents.

7. The night shift should end as early as possible.

• This recommendation is based on the finding that sleep times during the day are not arbitrary, but depend on the onset of sleep. Because of its circadian rhythm (the "internal clock"), the body tends to wake up around noon. The earlier sleep starts, the more likely it is to last longer.

• However, there is a direct contradiction between this recommendation and recommendation 6 where production lines are in continuous operation or where uninterrupted supervision is required in the service sector.

8. Rigid start times should be avoided in favour of individual preferences.

• Shift workers also have a growing need for greater control over the start and end of their working hours, as under flexitime. To meet this need, shift workers could, for instance, be given the opportunity to start their shifts within a defined time corridor, depending on individual preferences and circumstances (e.g. commuting time to the workplace). For example, the early shift could start between 5:30 a.m. and 6:30 a.m.

9. Long sequences of consecutive working days and the compression of working hours on a single day should be limited.

• Employees sometimes work long sequences of consecutive shifts without any days off to interrupt them. This arrangement is often found in hospitals, where shift schedules involving twelve consecutive working days without a day off are relatively widespread. Conversely, the compression of working hours on a single day means doing very long shifts, typically around twelve hours, which are common in professions such as the police or the fire service.
• Long sequences of consecutive working days and the compression of working hours on a single day often result in longer blocks of time off. For instance, twelve-hour shifts have the consequence that the employee works a total of thirty-six hours in just three days. For this reason, compressed working hours are often perceived positively by employees. However, the accumulation of stress and the resulting physical and psychological strain increase the likelihood of health problems. Stress accumulates not only on a single working day but also over the course of a working week. The level of stress depends on several factors, particularly the nature of the job. When the duration of shifts is determined, shift schedules should therefore take account of the nature and intensity of the work done.

The working day should only be extended if:

• the work task involves only a low level of stress (physical, mental),

• there is no need for additional overtime,
• the risks are limited if the employee makes an error,
• sufficient personnel are available,
• the maximum workplace concentration (Maximale Arbeitsplatz-Konzentration, MAK) values are adjusted accordingly,
• part of the working time is spent on standby duty.

10. Shift schedules must be predictable and clear.

• Once established, shift schedules should ideally be adhered to by the organisation to ensure predictability in employees' personal lives. It is important to avoid creating the impression that individual concerns are being neglected.
• It is also desirable to provide employees with a high degree of autonomy in shift planning. In this context, autonomy means being able to integrate individual preferences and wishes into the scheduling process. This increases employees’ satisfaction with the organisation of working time and has a positive effect on motivation.

Notes on implementation

• These recommendations do not all need to be addressed simultaneously. Nor do they have to be implemented in the order discussed above. Instead, each criterion should be evaluated individually and tailored to the specific needs of the organisation.
• Several factors should be taken into account when evaluating these recommendations. Legislation and collective agreements establish crucial parameters for the organisation of working time. In addition, operational considerations, employee preferences (working time patterns are always subject to mandatory co-determination within organisations), and ergonomic findings must be considered. However, it is not usually possible to meet all the criteria at the same time. The design of shift schedules is a task that has to take account of the trade-offs between the different criteria. The process is made more difficult by the fact that it is not entirely clear which criteria are most important or what order they should be addressed in. In principle, however, it must be expected that the specific aspects relating to the reduction of health risks will necessarily have to be given priority. Workloads should not be too high relative to employees’ working hours. Rest periods between shifts should be long enough to allow effective recovery. To avoid sleep deprivation, the number of consecutive night shifts should be limited. These criteria are primarily based on recommendations from occupational medicine. They are also, to a certain extent, reflected in legislation and are therefore basic requirements when planning shift schedules.
• Another important factor in the organisation of working time is "employee orientation". Ultimately, the weighting of the individual recommendations for action is also based on how they are viewed by employees. The wishes of the workforce determine which criteria are considered important and which are not. It is difficult to generalise about attitudes to these issues. In practice, employees’ preferences often vary considerably. For example, commuting options, leisure preferences, family circumstances, and the composition of the work group can be important. One critical issue of relevance to almost all changes in working time patterns is income security. Changes to working time that lead to a reduction in income usually meet with considerable resistance from employees. It is almost inevitable such changes will be rejected.
• In consequence, a new working time system should always be designed with the involvement of all those concerned within the organisation. In principle, the following key questions should be discussed during the consultations:
• What is the maximum tolerable shift length?
• Should night shifts be shorter? Or could night shifts even be made longer, for example to allow for more weekends off?
• Is it acceptable to change shifts at short notice in individual cases, for example to take a Saturday off?
• How heavy is the workload?
• How resilient are the employees? What is the proportion of older employees and employees with acquired disabilities? What is the proportion of employees with additional domestic responsibilities (e.g. children, family members who need to be cared for)?
• What options are there for the timing of shift changeovers? Would flexible start times be possible? What are employees’ commuting times? What are their personal preferences? What transport options are available?
• Are there sufficient opportunities to compensate for the additional strain of night work with compensatory time off? Is the current size of the workforce adequate?