This article recently appeared in OHS Canada

One of your top workers is rubbing his eyes, yawning and moving slowly. You know that “John” still has four more hours on shift in a safety-sensitive job. You ask him how he is and he responds: “I’m fine, just a little tired.” What do you do? Do you get him a cup of coffee? Make him take a break? Or do you tell John to just be safe out there? What actual written procedures do you have in place for your supervisors to follow?

Fatigue is not simply a state of feeling tired. Fatigue can be a hazard in and of itself, but what is often overlooked is how fatigue can elevate the risk of other hazards you’ve already identified. To prevent errors and incidents from happening, it takes more than just having a worker show up with eyes open.

While there are a number of personal reasons why a worker may be struggling with fatigue, at some point we have to start looking at the flaws in the system — not just the flaws in the worker.

The science is clear: workplaces need to understand their role in the promotion and mitigation of fatigue. The most important factor in their control comes down to the design of work schedules. There are two components to consider in a schedule design — the time of day that the work is being done (circadian factor) and the length of hours on and off duty (homeostasis factor).

Humans are not nocturnal

Based on our circadian rhythms, humans are a diurnal (day-oriented) species. This means we will always perform better and be more alert and safe when working during daylight hours, and get our best sleep during dark nighttime hours. We are at our worst between midnight and 6 a.m. when we are programmed for sleep, and suffer poor sleep when trying to sleep during daytime hours. There is also a dip in our rhythms in the early afternoon (the siesta period), which can also affect alertness and performance. Most importantly, research has demonstrated that less than three per cent of night workers show any physiological adaptation to night shifts. In other words, we have yet to figure out how to turn our species into nocturnal animals. So, while you may think you’ve adapted, the truth is, you’ve adapted to being in a state of impairment — it’s your new normal.

Night-shift risks

Recognizing that shift workers are at higher risk for fatigue and performance impairment, consider the following:

  • Do one or more shifts exceed 12 hours in a 24-hour period?
  • Do any shifts start or finish between the hours of midnight and 6 a.m.?
  • Do changes to a roster, or posting of shift assignments occur with less than two weeks’ notice?
  • Are complex or critical tasks scheduled during the high-risk zones?

The longer you’ve been awake, the more sleep pressure builds in the brain due to a depressant called adenosine. The result is that after being awake for 14 hours, sleepiness starts to set in. At 17 hours, you are the equivalent of .05 blood alcohol impairment (BAC). At 18 hours, you will be struggling to stay awake. At 20 hours, you are equivalent to .08 BAC, and your cognitive abilities drop by up to 40 per cent. Back to John. If he works a 12-hour shift, considerations would need to include when he woke up, length of his commute and any other factors that might influence how long he’s been awake, in addition to circadian factors.

If John’s on a night shift, that means a minimum of 12 hours off duty before his next shift. Ask yourself:

  • Do some extended hour shifts exceed 12 hours?
  • Are more than three consecutive 12-hour night shifts worked?
  • Is there less than 12 hours undisturbed rest after a 12-hour night shift?
  • Do employees work more than 60 hours in a seven-day period?
  • Are there irregular and unplanned schedules as a result of call-outs?
  • Is overtime unmonitored?

If you have identified flaws in the scheduling system, that doesn’t mean you have to throw it out. It does mean that you need to put a plan in place to mitigate the risk attached to those flaws.

Because being awake is not enough.

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