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Night shifts: Are they safe?

By Dave Rebbitt

Night shift work has been around for a long time. Night shift is inherently more risky than day shift for a variety of reasons, yet many industries need a night shift to function effectively. These familiar industries include law enforcement, medical facilities, construction, and the oil industry. Identifying the risks is fairly straightforward.  

Although necessary, night shifts are inherently less productive by at least five per cent. More than 18 per cent of workforces are engaged in some sort of night work with seven per cent engaged in permanent night work, according to an article in the Journal of Occupational Medicine.  

The risk of injury is also elevated by as much as 30 per cent. Rotating shift workers are more than twice as likely to have an incident compared to straight day shift workers.  


Darkness is the most obvious hazard. This risk is best phrased as the lack of light. There is not enough natural light at night and that alone can lead to a condition similar to Seasonal Affective Disorder where a lack of light causes, among other things, tiredness. Actually seeing at night is also a problem so supplemental lighting is required. For outside work this means portable light plants and smaller task lighting. 


Perhaps the biggest factor is fatigue, which is linked to the circadian rhythm. Everyone’s body slows down at night and our metabolism and alertness reaches low ebb between 3 a.m. and 5 a.m. This is similar to the dip many people experience in mid afternoon after a large lunch. 

There are some specific situations around fatigue. The first is for those moving to night shift from days. Without time for the body to adjust, these workers will experience intense fatigue and struggle to function for the first week on night shift. Starting a night shift “cold turkey” greatly elevates both the risk of an incident and the physical stress on the worker. Workers working the night shift must still deal with the natural fatigue caused by the circadian rhythm. Up to 20 per cent of workers are unable to adapt to shift work.

Fatigue can also result from the length of the shift. Shifts tend to be eight, 10, or 12 hours. The longer the shift, the more the risk of incident is elevated. Additionally, the timing of the shift rotation is important. A shift that runs from 6 p.m. to 6 a.m. is probably common and probably the most risky. The risk of incidents rise as the shift progresses. In rotating shifts that alternate between days and nights, the body needs time to adjust and failure to provide adequate time can risk fatigue on day and night shifts for those workers.


Workers on night shift are fewer in number than day shift and continue to work in facilities or areas designed for larger workforces. This makes supervising these workers more difficult as the supervisor may have many places where activities are occurring. Workers involved in activities like maintenance may also be working alone. So night shifts tend to suffer from lower supervision.


Driving is an often overlooked facet of night shift. Workers drive home at the end of the shift, which may still be in the dark. A lot of study has been done on commercial drivers and length of work. Research shows the sharply rising likelihood of an accident beyond 10 hours of driving. Reducing driving hours has reduced collisions.

For most people, a 12-hour shift and a one hour commute each way would push the limits of what most people would consider reliably safe. However, what if the worker was at a remote worksite and traveling two or three hours home? Night and rotating shift workers can be twice as likely to have an automobile accident.

Reducing the risk

Reducing or mitigating the risk is the only realistic option where night shifts are required. The following are some preventive measures: 

•Avoid rotating shifts: Constant adjustment of the circadian rhythm is fatiguing and stressful both physically and mentally.

•Provide more supervision to ensure workers are more closely monitored.

•Ensure lighting is adequate. Use full spectrum lighting where possible.

•Have more frequent breaks particularly during the dip in alertness in early morning.

•Allow workers time to shift their circadian rhythm forward towards night shift.

•Promote the use of carpooling and public transit to reduce the number of employees driving.

•Avoid assigning complex tasks to night shift.

Some other methods that may prove helpful — but may not be practical — include allowing for naps and providing additional safety personnel in addition to additional supervision.

Dave Rebbitt

Dave Rebbitt is the president of Rarebit Consulting providing services across Western Canada. With almost 30 years in health and safety, Rebbitt has built numerous health, safety, and environment management systems along with some innovative processes and even developed specialized PPE. He is an experienced speaker and writer on a wide variety of topics. He also develops and instructs courses at the University of Alberta OHS program. He can be reached through
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