Fatigue describes the feelings of tiredness, sleepiness, reduced energy and increased effort needed to perform tasks at the desired level. Fatigue in the workplace can be caused by the time of day, sleep deprivation and time on task. Fatigue can cause a worker to suffer from decreased vigilance leading to reduced productivity and increased safety risk. In the long term fatigued employees’ health can suffer leading to increased costs to employers and society.

Time of Day

Shift workers, especially those on the night shift, and those driving during night-time hours are particularly vulnerable to fatigue because of the body’s circadian rhythm, time of day has a profound impact on fatigue.

Shift Work

People are physiologically programmed to sleep at night and be awake and active during the day. Shift work can lead to a decrease the quantity and quality of sleep causing fatigue.

Employees on rotating shifts are less likely to adapt to the night shift which leads to sleepiness and fatigue. If a rotating shift is necessary, forward rotating shift is best.

Night-shift workers’ do not get as much sleep during their time off as daytime or evening workers. Over several consecutive night shifts, fatigue can build up and result in poor performance on the job.

Night Time Driving

Drowsy driving crashes typically occur during night time and early morning hours.

Time Awake

The physiological need for sleep goes up with time awake and goes down with time asleep.

Long Hours or Overtime

Working long shifts can cause fatigue and affect performance due to the body’s increased need to sleep.

Sleep Deprivation

People require adequate sleep (7-9 hours for adults) in order to function. Sleep debt, a cause of fatigue, happens when a person loses a sufficient amount of sleep or stays awake for an increasing period of time.

Sleep deprivation can accumulate, and large sleep debt may result in chronic fatigue.

Sleep Problems

Sleep disorders, chronic diseases and medications can decrease sleep quantity and quality, increasing fatigue.

Research shows roughly 60% of shift workers complain about sleep loss and sleeping problems.

Sleep deprivation in combination with working at night may further exacerbate the adverse effects of fatigue.

Approximately 23% of works suffer from insomnia.

Time on Task

Individuals will experience fatigue the longer they conduct a specific task. This fatigue can manifest as sleepiness, muscle tiredness or mental tiredness.

A person’s ability to remain focused on simple and repetitive tasks is limited. Examples are long-haul driving, working on an assembly line, baggage screening, scanning, inspections, quality control, etc.

The “time-on-task effect” is the gradual increase in the amount of effort required to maintain the same level of performance on a task over time. In other words, the longer we are required to perform a tedious task, the more our attention, speed, and accuracy decline.

Time-on-task fatigue becomes worse as a result of extended wakefulness, night work, or both.

Research shows optimal duration for safe highway driving is under 90 minutes before sleepiness and time-on-task related decreases in performance can occur.

Personal Factors

Some individuals are more prone to fatigue than others. Personal factors such as age or medical conditions can play a role.

Some studies show that people over 40 years old have a harder time adjusting to night shifts due to circadian rhythm.

Sleeping disorders, including insomnia and sleep apnea, are associated with reduced safety and productivity in the workplace and increased risk of traffic incidents.

Other sleep disorders affecting sleep quality (e.g., narcolepsy, restless legs syndrome) and chronic health conditions (e.g., asthma, chronic obstructive pulmonary disease, allergic and non-allergic rhinitis, rheumatoid arthritis, osteoarthritis, chronic fatigue syndrome) may further exacerbate the level of performance impairment associated with fatigue.

Other personal factors that may contribute to fatigue include; gender, socioeconomic factors, physical and mental health, endurance, genetic predisposition, need for sleep, diet and nutrition, physical activity level, body mass index, personality traits, substance use, medication use, family and marital status, job status, fatigue awareness.

Work Factors

Some jobs are more prone to fatigue due to task-related factors, environmental factors and organizational factors.

Task-related Factors

The type of task an employee does can affect his or her level of fatigue including; the physical and mental demands of the task as well as an employee’s level of experience with the task.

Environmental Factors

Characteristics of the work environment may contribute to the occurrence of fatigue. Some factors known to increase the risk of fatigue among workers are noise and poor indoor air quality. On the other hand, exposure to bright light has been shown to increase alertness and reduce fatigue

Organizational Factors

Organizational factors like safety culture, employee engagement, leadership commitment and supervisor support can help prevent fatigue-related incidents. Other factors that can affect employee fatigue are; company size, type of industry, absence of a fatigue risk management system, work scheduling policies, and employee compensation (payment by task, hour or overtime).

General Effects

Fatigue caused by time of day, sleep debt and time on task have several detrimental effects:

An individual will experience a decrease in their ability to perform basic cognitive functions resulting in a decline in a number of vital activities such as attention, vigilance and memory.

Decreases in cognitive performance lead to a decline in job and safety performance. An individual will become less productive thus increasing their risk of a negative safety incident.

A chronically fatigued individual will become more at-risk to health problems like cancer and heart disease. Research has demonstrated that fatigued individuals are an economic strain to themselves, employers and society due to decrease productivity, increased risk of negative safety outcomes, and increased illness.

Cognitive Performance

Extensive research has shown that fatigue, as a result of shift work and sleep deprivation, leads to decreases in cognitive performance, short-term memory, concentration, performance speed, reaction time, executive function, psychomotor activity, attention, vigilance, alertness, accuracy, mathematical calculation and judgment.

Three of the most well-documented detriments of fatigue are decreases in attention, vigilance, and memory performance.

Research shows night shift workers experience disruptions in cortisol and melatonin, affecting their sleep quality and increasing their fatigue.

Losing small amounts of sleep over time can be detrimental. A person who sleeps 6 hours a night for 2 weeks performs similarly to someone who loses one full night of sleep.

Work Performance

Work performance, including productivity, decreases as employees become fatigued. Fatigue-related decreases in work performance have been observed in those on shift work, rotating shifts, night shift, early start times, working overtime or long hours, and employees with sleeping problems.

Work performance, including productivity, decreases as employees become fatigued.

Worker productivity decreases between 6% to 2.5% depending on level of tired or sleepiness.

Declining work performance from fatigue has been observed in those on shift work, night shift, rotating shift, working overtime or long hours, sustained time on task and employees with sleeping problems.

Safety Performance

Workplace safety performance decreases as employees become fatigued. Individuals working night shift, rotating shifts or long hours are at a higher risk for safety incidents.

Sleeping Disorders

Poor sleep is a strong predictor of negative workplace safety incidents. Individuals with sleeping disorders, such as insomnia or obstructive sleep apnea are more likely to be involved in a negative workplace safety incident.

Approximately 13% of work injuries could be attributed to sleep problems.

Time of Day

Numerous studies have shown a higher safety risk among night shift compared to day shift.

A nearly 30% increased risk of negative safety incidents happen during night shifts compared to morning shifts.

Night shifter workers are 3 times more likely to be injured in a workplace incident compared to day shift workers.

Several studies suggest rotating shifts may have a greater safety risk than non-rotating shifts due to synchronization.

Long Hours

Research shows safety risk increases with shift duration and number of hours worked per week.

One study demonstrated a two-fold increase in safety risk in a 12-hour shift compared to an 8- hour shift.

Traffic Crashes

Studies show fatigue is a contributing factor to traffic crashes.

It is estimated that 19% of vehicle crashes are attributed to drowsy driving.

One study showed the odds of being in a crash or near crash were nearly 3 times higher when the driver was drowsy.

Individuals suffering from sleeping disorders, such as sleep apnea, are at a high risk of traffic crashes.

Health Consequences

Fatigued individuals and shift workers are at a higher risk of health problems including, but not limited to, depression, cardiovascular disease, obesity and diabetes.

Shift workers, those who work long hours and those who are sleep deprived, are at higher risk of vehicle crashes, obesity, psychological disorders such as anxiety and depression, musculoskeletal disorders, reproductive problems, diminished immune response and numerous chronic diseases including hypertension, cardiovascular disease, gastrointestinal disease, cancer, diabetes.

Economic Consequences

Research shows fatigue causes decreased productivity, reduced safety performance and poor health which can lead to increased costs to employers and society.

Fatigue-related decreases in productivity costs employers between $3,156 and $1,293 per employee annually.

Insomnia costs the Australian economy up to $10 billion per year.

Employees with untreated sleeping disorders, such as insomnia, incur significantly greater direct and indirect health care costs.

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