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anses

French Agency for Food, Environmental and Occupational Health & Safety

ANSES confirms the health risks associated with night work

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News of 22/06/2016

ANSES received a formal request to assess the health risks for professionals exposed to atypical working hours, in particular night work, whether regular or irregular. The Agency’s expert appraisal identified proven risks of sleep disorders and metabolic disorders, and probable carcinogenic risks, cardiovascular disorders and psychiatric disorders for the workers concerned. Surveys on working conditions conducted among employees working at night usually indicate more numerous physical hardship factors and work constraints.

In its conclusions, the Agency considers that the use of night work may be justified for situations where there is a need to ensure the provision of services of social value or the continuity of economic activity.It nevertheless advocates optimising the ways in which night work is organised, in order to minimise its impact on the personal and professional lives of employees. It stresses thatanything that reduces the desynchronisation of biological rhythms and sleep debt is favourable in principle. Specific organisational recommendations, on which there is not always a scientific consensus, should also be examined collectively in the appropriate social dialogue bodies. The findings of this expert appraisal are intended to provide useful insight for these discussions, along with those expected to result from the bill seeking to establish new freedoms and new protections for companies and workers currently being examined by the French Parliament.

 

Today, a large number of workers are affected by so-called "atypical" working hours and rhythms. This particularly concerns shift work, where employees form different teams that take over from each other on a given workstation without ever overlapping, and night work, performed between 9pm and 6am (on fixed or rotating hours).

In 2012, the population concerned by regular or occasional night work represented 3.5 million people, or 15.4% of employees. Night work concerns various sectors of activity. It may be introduced to ensure the continuity of services of social value (health services, police officers on call, other surveillance services, etc.) or may be a work organisation method (a company that wishes to maximise the profitability of its equipment by getting machines and people to work around the clock).

Employees who work at night are generally subjected to more numerous physical hardship factors, greater time pressure (hours, rhythm constraints, deadlines, etc.), and more frequent tensions with their colleagues or the public. However, the organisational characteristics and conditions of night work may vary, particularly from one sector to another, and this may decrease or amplify the effects of night work on the health of the employees.

The International Agency for Research on Cancer (IARC) studied the impact of this organisation of work on the risk of cancer, leading it to add shift work that disrupts circadian rhythms to the list of agents that are "probably carcinogenic" (Group 2A) in 2007. In France in 2012, the French National Authority for Health (HAS) also published recommendations on good practices for monitoring shift and/or night workers.

In this context, ANSES received a formal request from the French Confederation of Christian Workers (CFTC) to assess the health risks for professionals exposed to atypical working hours, especially those subject to night work, whether regular or irregular. The opinion it is publishing today reports on the assessment of the health risks to which professionals are exposed when working night hours. This work will be supplemented by a second component on the health effects potentially associated with other forms of atypical working hours.

 

Proven, probable, and possible health effects

The conclusions of this expert appraisal confirm the health risks associated with night work. It may generate effects on the health of workers due to the disruption of their biological rhythms. During night work, a desynchronisation occurs between the circadian rhythms that are aligned with daytime hours, and the new activity-rest/awake-asleep cycle imposed by the night work. This desynchronisation is also promoted by environmental conditions that are not conducive to sleep: daylight during rest, daytime temperature usually higher than at night, higher noise levels during the day, social and family obligations.

Thus, the results of the expert appraisal highlighted the health effects of night work, with different levels of scientific evidence:

  • the effects on drowsiness, the quality of sleep and the reduction of total sleep time, and metabolic syndrome are proven;
  • the effects on psychological health, cognitive performance, obesity and weight gain, type 2 diabetes and coronary heart diseases (coronary ischaemia and myocardial infarction) are probable;
  • The effects on dyslipidaemias (excessive concentrations of certain lipids in the blood), high blood pressure and ischemic stroke, are possible.

 

Regarding cancer, the expert appraisal concludes that there is a probable effect of night work on the risk of cancer. In particular, there is evidence supporting an excess risk of breast cancer associated with night workthat seems to be due to the disruption of biological cycles. The expert appraisal stresses the existence of physiopathological mechanisms that may explain the carcinogenic effects associated with disruptions of biological rhythms.

The Agency's work also shows that the frequency and severity of accidents occurring during night work are generally higher. 

 

Modulating factors

However, the effects of night work on the health of the employees subjected to it are not unambiguous and systematic. They depend on a combination of factors based on the employees' individual characteristics (chronotype), social and family characteristics (the possibility of organising their social and family life), and the characteristics of the work and work situation.

These multiple factors can decrease or amplify the effects of night work on the health of the employees.

 

The Agency’s recommendations

The Agency begins by reiterating the first principle of removing the hazards to which workers are exposed, in the framework of the general principles of risk prevention laid down by the French Labour Code.

In light of the results of its expert appraisal, the Agency considers that the use of night work may be justified for situations where there is a need to ensure the provision of services of social value or the continuity of economic activity (hospitals, public services, etc.).

The Agency advocates optimising the ways in which night work is organised, in order to minimise the impact on workers' personal and professional lives. In particular, anything that reduces desynchronisation and sleep debt is favourable in principle, but specific organisational recommendations, on which there is not always currently a scientific consensus, should be examined collectively in the appropriate social dialogue bodies.

The Agency also recommends conducting a review of practices in the field designed to protect the health of night workers (maximum duration of daily work, break times, minimum daily rest, compensatory rest, medical supervision, etc.).

Moreover, the current regulatory framework should be adapted to protect the health of night workers, and should evolve, if applicable, taking the European dimension into account. The Agency emphasises that there is currently no definition covering the continuity of economic activity in the regulations.

Lastly, ANSES advocates assessing the health impact of the effects of night work (number of cases for each potential disease in the worker population), and assessing the social costs associated with the use of night work (work stoppages, occupational disease, absenteeism, etc.) compared to the potential benefits.