Too short shift intervals cause unnecessary sleep deprivation and stress in shift work. Employees must always be able to recover sufficiently during working days and between them. This is required also by the Occupational Safety and Health Act, which raises recovery as one of the most important matters in assessing the stressfulness of working time.

According to the Finnish Working Hours Act, there should be at least eleven hours between shifts in order to ensure sufficient sleep and rest. However, in shift work, which is becoming increasingly common, shift intervals shorter than eleven hours are permitted when organizing the work requires it. In practice, short shift intervals have become a practice that is unnecessarily stressful for the employees of many organizations.

Our recent Scandinavian study focused on employees in the care sector. In Finland, nearly half (47%) have many shift intervals that are shorter than eleven hours (at least 13 per year). In Denmark, only one in six (16%) people working in corresponding occupations have short shift intervals.

The Finnish Institute of Occupational Health’s Työelämätieto service shows that an average of 16% of all shift intervals are under eleven hours long. The number has not changed in the last 10 years. However, women have more short shift intervals than men – and women under 25 have the most.

Helsinki social welfare and health care sector reduced short shift intervals

There are big differences between cities and hospitals in how shift planners have been instructed when planning shifts. In Helsinki, social welfare and health care tried to reduce short shift intervals already in the mid-2000s and made an administrative decision regarding good shift planning in 2011. Reducing short shift intervals was one of the central recommendations of the decision. Thanks to the programme, short shift intervals started declining sharply (see graph) compared to other Kunta-10 organizations. According to our preliminary results, good shift planning has also reduced psychological stress in Helsinki.

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200820092010201120122013201420152016%02468101214161820< 11-hour shift intervals as share of allshift intervals, %Kunta10Helsinki

Graph 1. Change in short shift intervals in the social welfare and health care sector in Helsinki compared to other Kunta-10 organizations.

How do short shift intervals impact health and well-being at work?

The Finnish Institute of Occupational Health has researched the link between short shift intervals and health in the Finnish social welfare and health care sector, based on working time data from the Titania shift planning software. Of all the researched features of working time, short shift intervals had the strongest connection to health and occupational safety. If there were many short shift intervals of under eleven hours, the number of both occupational accidents as well as short and long sickness absences increased. In recent years, there have been similar results in several other international studies. According to our studies, shift intervals shorter than eleven hours are also still connected to trouble falling asleep and tiredness both at work and at home. In addition, short shift intervals also weakened the experience of work-life-balance.

How many short shift intervals can you safely plan?

The Finnish Institute of Occupational Health has published so-called traffic light recommendations for assessing the stressfulness of working time in shift work. According to our research-based recommendations, 5–8 short shift intervals per 3-week shift period leads to excessive stress, and 9 or more already lead to so-called strongly excessive stress. This should not be accepted in a duty roster under any conditions. However, a few short shift intervals in a three-week period do not have significant detrimental effects. There can be some short shift intervals in a duty roster, but the limit values of excessive stress should not be exceeded.