What does fatigue look like?

01 Jun 2022 The Navigator

Fatigue at sea has gained increasing attention over the last few years – and generated research to match. Current regulatory requirements mainly focus on hours of work and rest. However, other factors come into play, such as irregular work hours and having to stay at your workplace to sleep. Dr Michelle Grech from the Australian Seafarers Welfare Council looks at why sleep matters, and how you can tell when you or your colleague might be affected

Sleep quantity and quality are critical factors in determining how fatigued you are likely to be at any given time. Generally, we require between seven and nine hours of continuous sleep per day to perform adequately. Repair, restoration and maintenance of physical and mental functions are all undertaken during sleep, which is why it is so important.

Sleep debt
When we do not get enough sleep during the night, or over a series of consecutive nights, we build up what is called sleep debt. This results in high levels of fatigue. It’s common in seafaring to get some sleep but not enough, night after night, possibly for weeks or months. Studies point to a 45% increase in errors by the fourth consecutive night shift and a 90% increase in errors by the seventh night on duty. Sleep debt can also lead to ‘micro-sleeps’ which is when you ‘nod’ off or even fall asleep completely while working.

Important studies showed that people who went without sleep for 17 hours recorded similar cognitive impairment levels to people with a blood-alcohol concentration of 0.05% – enough to affect your performance when driving, for example. This increased to 0.1% when subjects were awake for 23 hours or more. Over the longer term, sleep debt also impacts on physical and mental health.

Sleep debt is made more intense when you are required to work at night and sleep during the day. Due to our circadian rhythms, daytime sleep is often shorter and of lower quality. We are biologically programmed to be active during the day and to sleep at night. For many people, shift working patterns often conflict with their biological clock – and contribute to reducing sleep quantity.

Working conditions
Working too long without sleep at any time of day contributes significantly to tiredness and fatigue. In general, the longer you remain awake, the stronger your drive for sleep becomes, and the higher your levels of fatigue grow. The risk of an accident in the twelfth hour of work is more than double the risk of an accident in the eighth hour of work, according to one study. Additionally, the longer you have continuously been on a single task without a break the more likely you will be fatigued. Many people work more than 12 hours per day, sometimes with limited breaks. A seafarer’s working week usually exceeds 70 hours.

One concern is that, over the past few years, evidence points to an excessive increase in working hours on ships. Worst still is that ‘pressure’ on seafarers to ‘toe the line’ by some shipping companies and under-report actual hours worked (basically hiding breaches in the hours of work and rest requirements) is becoming the ‘norm’ for many.


Working onboard a vessel also introduces conditions that are seldom present in other workplaces. These include noise, lighting, vibration, ship motion, temperature and other factors known to disturb sleep. Any sleep that people do manage to get is often disturbed. This leads to poor quantity and quality of sleep. Consequently, the continuous presence of fatigue remains highly likely.

How can you tell someone is fatigued?
Short-term risks of fatigue are mainly related to an immediate impact on safety. For example, your decision-making might be impaired in a collision situation, or you might fall asleep and miss a course change, resulting in a grounding. As a rule, elevated levels of fatigue are associated with the following physical symptoms and behavioural indicators:

  • decreased alertness
  • lessened ability to sustain attention
  • slower reaction time
  • poor hand-eye coordination
  • difficulties with communication
  • reduced vigilance
  • impaired decision-making
  • micro-sleeps
  • mood swings
  • compromised short-term memory
  • impaired judgement
  • lethargy and an increase in error rates.

What effect does fatigue have on a person’s health?
There are many physical health outcomes that result from continuous exposure to long working hours (i.e. 60 hours or more per week), sleep debt and fatigue. Incomplete recovery from work has been shown to increase overall risk of death from cardiovascular diseases. Other physical health risks include gastrointestinal problems such as peptic ulcer and irritable bowel syndrome; a higher risk of coronary heart disease, increased blood pressure and weight gain.

In addition, you are at a higher risk of displaying negative behaviours such as smoking or poor diet. Psychosocial effects include needing longer to recover and regain energy after work.

Another more insidious impact that fatigue has is that on mental health. We are currently seeing a rise in mental health concerns in shipping. Problems with mental health appear as reduced performance, impaired alertness and / or a sense of weariness, burnout and exhaustion. Even before COVID-19 hit, it was widely acknowledged that people working at sea were at a higher risk of mental health issues due to their work hours, watch schedules and high workload. There is now strong evidence to suggest that increased levels of depression and anxiety in the maritime industry have been further exacerbated due to the pandemic.

Given the inevitable and ongoing risks associated with the onset and impact of fatigue, the maritime industry needs to ensure that people working at sea are properly supported, and that their work demands do not require them to continuously extend themselves to the limit of their capabilities. Only then can the risk of fatigue be properly managed.