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International research: Increased health and accident risk during night work

Night work creates a considerably higher accident risk than day work, and can reduce situational understanding and reaction times to a degree equal to the effect of a blood alcohol level of 0.5-1. The transition between night and day creates sleeping ailments and disturbs the circadian rhythm. In general, research shows that night and shift work increases the risk of several serious diseases. An effort is underway to investigate to what extent these findings are relevant to the petroleum activities in Norway.

On 15 March, the results of a number of studies were presented and summed up during the Petroleum Safety Authority Norway's expert seminar on HSE consequences of working hour schemes used in the petroleum industry.

Serious illnesses
The results show a clear correlation between night and shift work and several serious illnesses. For instance, night work increases the risk of cardiovascular disease by 30 to 60 per cent, compared to day work. The increase in risk is equally high for breast cancer, while night and shift work means an increased risk of occupational accidents of up to 60 per cent.

In the offshore petroleum activities, the following working hour schemes mainly apply (2005/2006):

  • Fixed dayshift (approx. 43 per cent)
  • Fixed night shift (2.4 per cent)
  • Whole shift 14N or 14D - two whole weeks night work or two weeks day work (15.5 per cent)
  • Swing shift 7N-7D- seven nights, then seven days (12.5 per cent)
  • Swing shift 7D-7N - seven days, then seven nights (5.1 per cent)
  • Varying schemes (21.6 per cent)

In the petroleum activities on land, the focus has been on the so-called commuter schemes which are used in major construction projects. The commuter schemes can mean working hours of up to 12 hours daily for 14 consecutive days, followed by three weeks off.

Risk reduction
Professor Mikko Härmä at the Finnish working environment institute summed up several surveys which support the claims of the increased risk of accidents and health complaints from night work, shift work and overtime.

The professor also accounted for how lack of sleep or reduced quality of sleep affects the ability to perform, alertness and mental/cognitive abilities. In addition, Härmä pointed out several conditions which affect the ability to adapt continuously to new sleep-wake cycles; including exposure to (day)light, diet and physical activity.

Not least, research shows that sleep before the first night shift and short sleeping breaks during the working hours may have great importance as a risk-reducing measure.

Furthermore, the petroleum industry should avoid use of overtime in periods with extended work periods, and overtime should especially be reduced among employees who carry out safety-critical work.

Likewise, safety-critical tasks should not be performed during the night shift, and the employees must be offered safe transport home after night work.

Recommends whole shifts
Dr. Katharine R. Parkes at the University of Oxford accounted for research surrounding health and safety effects of working hour schemes, for instance on the British shelf.

Katharine R. Parkes recommends whole shifts (14D/14N) as the preferred working hour scheme. Several studies indicate that a slow shift rotation (14 nights and 14 days in alternating work periods) means less sleeping problems and work injuries, less use of sleeping pills and fewer reported health problems than swing shifts - regardless if the swing shift starts on a day or a night.

On the other hand, it may take up to six days to adapt the sleep-wake cycle to day shifts following night shifts prior to the period off. With swing shifts (7N-7D), the sleep-wake cycle is adapted to being awake in the daytime when coming home, and the sleeping problems are avoided in the free period.

Surveys show that offshore workers in swing shifts who start with night shifts will be out of sync with the sleep-wake cycle in at least five of the seven night shifts. When the sleep-wake cycle has adapted to night work, it has to adapt to daytime again.


Need for knowledge
Härmä supports Parkes findings that there are several unfortunate aspects of swing shifts. The researchers believe that employees returning home from night shift must be accommodated better, in the form of safe transport home and guidance on how the sleep-wake cycle can more easily be turned around, for instance by using daylight therapy.

Parkes pointed out the need for more knowledge on the consequences of extended working periods (three weeks). She also called for more knowledge on the effect of working hours exceeding 84 hours per week. Weeks with up towards 100 working hours are especially relevant for people in leading positions.

Among the speakers were also department director and professor at the National Institute of Occupational Health (STAMI), Stein Knardahl. He described how shift work can affect bodily functions, mental and physical health, and the complexity of the interaction between working hours and performance, health, leisure time, sleep, rest and the relationship to family and friends.

The seminar on working hour schemes was an important milestone in the project of elucidating what research there is on HSE consequences of the working hour schemes in the petroleum activities.

The project is carried out in close cooperation with the employers and employees - with the conference as an important venue for comments and debate. Representatives from the employer and employee organisations, research milieus and the authorities (PSA and the Norwegian Labour Inspection Authority) were among the participants and speakers.

The request for the PSA to map the knowledge status and where more insight is required comes from the Ministry of Labour and Social Inclusion (MLS). The need for more knowledge has also been pointed out in Storting White Paper No. 12 (2005-2006) relating to health, environment and safety in the petroleum activities (the HSE White Paper).

The working hours project will be documented in a report to the MLS by the end of April. The intention was not to conclude which schemes should be recommended to the industry.

The report will sum up the knowledge status and point out the areas where there is a need for more research. The report will also be an important contribution in areas where the present knowledge is adequate, such as the development of regulations.

The presentations in English can be found in the link box

Contact in the PSA:
Principal Engineer