Fatigue is the mental and/or physical state of being weak and tired. Mental and physical fatigue is different, but the two will often exist together. A person becomes mentally tired if they are physically exhausted for a long period. A person being unable to function physically at their normal levels manifests physical fatigue Jackson & Earl, 2006.
Mental fatigue will manifest itself by a sleepy feeling and inability to concentrate properly. In medical terminologies, fatigue is not a sign, but rather a symptom. This means that a person suffering from fatigue is able to feel and describe the condition. Experts have indicated that around 10% of people globally suffer from persistent tiredness at any one time. Females are more prone to persistent tiredness than males. It is not easy to define fatigue in humans because of its large variability of causes. The causes of fatigue range from circadian rhythm disruption to boredom to heavy physical exertion John A Caldwell, 2005.
In nonprofessional terms, fatigue is defined as weariness. For a more accurate definition fatigue is a condition that is characterized by increased discomfort that leads to loss of power, a lessened capacity to work, the capacity to respond to stimulation, or reduced efficiency of accomplishment, and this is normally accompanied by a person feeling tired and weary.
The consequences of fatigue are insignificant for an average person, but for persons working in safety-related environments like piloting an aircraft, operating a motor vehicle, running a nuclear reactor, or performing surgery the consequences can be disastrous. In the aviation industry, fatigue is an important factor, which is associated with shift work and loss of sleep. Long duty cycles can cause flight crews to become careless, inefficient, and inattentive Jackson & Earl, 2006.
According to John A Caldwell et al. (2009)
aircrews suffer from fatigue due to irregular work-rest cycles, transmeridian flights, and other work related factors. The frequent loss or disturbance of sleep experienced by the flight crews also leads to fatigue. Fatigue has led to errors, incidents, and other problems in the aviation industry. According to NASA, fatigue attributed towards 21% of the reported aviation incidents. Crews flying all aircraft sizes face fatigue problems, and this is a continuing problem.
Causes of the problem
There has been a significant evolution in the operational demands and aviation technology, but the need for sleep by the human operators has remained. No amount of technology can counter the need for sleep especially if the technology requires a human operator. Fatigue can degrade many aspects of performance, including decision-making, judgment, reaction time, memory, selective attention, fixation, concentration and mood. Avers and Johnson (2011)
posits that the low arousal that sleep loss produces is accompanied by greater decrement in performance on simple tasks. With the simplification of the aviation process by technology, it has contributed towards this performance decrement. The amount of sleep required by individuals differs, but studies have suggested that most people require around eight to nine hours of sleep per night. Non-shift workers generally sleep more than shift-workers. Pilots claim they need at least 7.5 hours of sleep a night. Sleep timing influences the duration of sleep. Hence, the crossing of time zones can lead to cumulative sleep deprivation. People have the capability to deal with small amounts of fatigue, and catching up on a night's sleep will assist in working it out of their system. However, the continuous accumulation of fatigue could lead to potentially dangerous effects. Circadian rhythms and sleep debt are the two main causes of fatigue.
A person's body temperature, human error, alertness, and sleep tendency follow a 24-hour pattern. The body has a steady 24-hour biochemical, behavioral, and psychological rhythm. These rhythms are the circadian rhythms. Human beings are diurnal creatures, meaning they are awake in the daytime, and they sleep at night. Exposure to light affects the human body clock especially the early morning light. A person's circadian rhythms are very reliable such that even if the person is removed from their 24-hour rhythm of day and night, the rhythms continue to run. Circadian rhythms affect aviation workers especially those working the night shift. Even with enough sleep during the day, the workers still experience fatigue while working. This is not caused by their lack of enough sleep, but rather by their natural circadian rhythms.
Understanding the circadian rhythms is vital especially in the aviation industry. The managers would be aware of what their employees experience and will develop strategies that would mitigate the risks associated with circadian rhythms. In the regulation of sleep, circadian rhythms play a vital role. There are chemical changes naturally occurring in the body when it is preparing to sleep. This typically occurs between 8pm and midnight. At around 3am, a person's body temperature will reach a low point, and then it begins to rise steadily as the body prepares for the day ahead. This will occur way before most people are awake. Managers need to recognize that the most critical time for their shift workers is between 2am and 5am. This is the window of circadian low. A person's body temperature is lowest at this time and their mental alertness poorest. The likelihood of employees making errors increases at this time. Aviation workers also experience this circadian low moment and the flight crews are most likely to cause incidents. During the circadian low moment, sleepiness reaches its peak. This time a person will feel tired, and they will start to experience bouts of sleep. If piloting an aircraft, the pilot is at a disadvantage if he starts to doze off. They might interfere with flying instruments unknowingly or might be unable to respond quickly to any mishap that occurs.
Another peak in sleepiness occurs between 3pm and 5pm. This is the afternoon nap window for most people. A person whose sleep is disturbed, or had a restricted sleep at night, will find it hard to stay awake in the afternoon nap window the next day. Taneja, 2007()
argues that employees affected by the circadian rhythm and have a can-do attitude, will struggle to stay awake and continue to perform their tasks as normal. This is dangerous, as the employee would have a slow reaction speed, prone to errors, and decision-making is poor. The employees need to understand their circadian lowest time and avoid performing safety critical work. This will reduce the number of incidents on the ground, but in the air, things are different. Pilots and flight crews have to remain alert at all times as any loss of consciousness can have severe consequences.
Adults need around seven to eight hours of sleep a night, but this need varies between people Caldwell Jr., 1997.
A century ago, people slept for around nine hours a night this was before the widespread usage of electric lighting. Today, work commitments, television viewing habits, and family demands combine to limit the amount of time a person sleeps a night. In the busy aviation industry, there are many people suffering from sleep deprivation, and they are not aware of it. Suffering from extreme sleep deprivation could have severe health effects, but mild sleep deprivation can even affect an employee's health and their ability to perform normal simple tasks at work and their personal lives Signal, Ratieta, & Gander, 2006.
Sleep debt builds up every time a person obtains less than normal sleep. With every successive night of inadequate sleep, a person adds up their sleep debt. Reducing sleep by only one hour a night on several nights could reduce a person's mental capacity.
Shift workers who work at night have to sleep during daylight hours, and this causes them to build up on sleep debt. Daytime sleep is brief and of poor quality, when compared to night sleeps. This indicates that the workers will increase their sleep debt if they work the night shift for long. Providing the shift workers with alternating schedules after a full day off will ensure they clear their sleep debt John A. Caldwell, 2012.
Aviation workers have no option since the industry operates 24-hours a day. Therefore, there will always be workers in the night shift. To reduce sleep debt, shift workers operating during the night should ensure that their bedroom do not allow any light during the day. Light affects a person's sleep patterns and reducing the amount of light will increase the person's sleep time. Research has shown that shift-workers experience one to two hours of sleep loss every 24-hours.
Family commitments and nature of work will deny a person enough sleep, which will increase their sleep debt. Other factors can lead to sleep debt like drugs, alcohol, and medical conditions. Insomnia, restless legs syndrome, sleep apnoea, and periodic limb movements are medical conditions that can interfere with a person's sleep patterns and time.
Scope and magnitude of chronic fatigue
A majority of people in the aviation industry see fatigue as normal and unavoidable. They argue and…