Effects of fatigue on safety

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Why the hours of service are important: a graph outlining the relationship between number of hours driven and the percent of crashes related to driver fatigue. Source: Federal Motor Carrier Safety Administration Hours of service FMCSA study.svg
Why the hours of service are important: a graph outlining the relationship between number of hours driven and the percent of crashes related to driver fatigue.
Source: Federal Motor Carrier Safety Administration

Fatigue is a major safety concern in many fields, but especially in transportation, because fatigue can result in disastrous accidents. Fatigue is considered an internal precondition for unsafe acts because it negatively affects the human operator's internal state. Research has generally focused on pilots, truck drivers, and shift workers.

Contents

Fatigue can be a symptom of a medical problem, but more commonly it is a normal physiological reaction to exertion, lack of sleep, boredom, changes to sleep-wake schedules (including jet lag), or stress.

In some cases, driving after 18–24 hours without sleep is equivalent to a blood alcohol content of 0.05%–0.10%. [2]

Types

Fatigue can be both physical and mental. Physical fatigue is the inability to continue functioning at the level of one's normal abilities; a person with physical fatigue cannot lift as heavy a box or walk as far as he could if not fatigued. [3] [4] [5]

Mental fatigue, on the other hand, rather manifests in sleepiness or slowness. A person with mental fatigue may fall asleep, may react very slowly, or may be inattentive. With microsleeps, the person may be unaware that he was asleep. Without proper amount of sleep, it will feel like certain tasks seem complicated, concentration will drop and ultimately result in fatal mistakes [6]

Factors

The Federal Motor Carrier Safety Administration identifies three main factors in driver fatigue: Circadian rhythm effects, sleep deprivation and cumulative fatigue effects, and industrial or "time-on-task" fatigue.

In addition to the primary factors identified by the FAA, other potential contributors to fatigue during transportation have been identified. These include endogenous factors such as mental stress and age of the vehicle operator, as well as exogenous or environmental stressors, such as the presence of non sea-level cabin pressure in-flight, vehicle noise, and vehicle vibration/acceleration (which contributes to the sopite syndrome). Many of the exogenous contributors merit further study because they are present during transportation operations but not in most lab studies of fatigue.

In aviation

The International Civil Aviation Organization (ICAO) that codifies standards and regulations for international air-navigation defines fatigue as: "A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload (mental and/or physical activity) that can impair a crew member's alertness and ability to safely operate an aircraft or perform safety related duties." [11]

Human factors are the primary causal factor aviation accidents. [12] In 1999, the National Aeronautics and Space Administration, NASA, testified before the U.S. House of Representatives that pilot fatigue impacts aviation safety with "unknown magnitude". The report cited evidence of fatigue issues in areas including aviation operations, laboratory studies, high-fidelity simulations, and surveys. The report indicates that studies consistently show that fatigue is an ongoing problem in aviation safety. [13] In 2009, Aerospace Medical Association listed long duty work hours, insufficient sleep, and circadian disruptions as few of the largest contributing factors to pilot fatigue. [14] Fatigue can result in pilot error, slowed responses, missed opportunities, and incorrect responses to emergency situations.

A November 2007 report by the National Transportation Safety Board indicates that air crew fatigue is a much larger, and more widespread, problem than previously reported. [15] The report indicates that since 1993 there have been 10 major airline crashes caused by aircrew fatigue, [16] [17] resulting in 260 fatalities. Additionally, a voluntary anonymous reporting system known as ASAP, Aviation Safety Action Program, [18] reveals widespread concern among aviation professionals about the safety implications of fatigue. The NTSB published that FAA's response to fatigue is unacceptable and listed the issue among its "Most Wanted" safety issues. [19]

Safety experts estimate that pilot fatigue contributes to 15-20% of fatal aviation accidents caused by human error. They also establish that probability of a human factor accident increases with the time pilots are on duty, especially for duty periods of 13 hours and above (see following statements):

"It is estimated (e.g. by the NTSB) that fatigue contributes to 20-30% of transport accidents (i.e. air, sea, road, rail). Since, in commercial aviation operations, about 70% of fatal accidents are related to human error, it can be assumed that the risk of the fatigue of the operating crew contributes about 15-20% to the overall accident rate. The same view of fatigue as a major risk factor is shared by leading scientists in the area, as documented in several consensus statements." [20]

"For 10-12 hours of duty time the proportion of accident pilots with this length of duty period is 1.7 times as large as for all pilots. For pilots with 13 or more hours of duty, the proportion of accident pilot duty periods is over five and a half times as high. [...] 20% of human factor accidents occurred to pilots who had been on duty for 10 or more hours, but only 10% of pilot duty hours occurred during that time. Similarly, 5% of human factor accidents occurred to pilots who had been on duty for 13 or more hours, where only 1% of pilot duty hours occur during that time. There is a discernible pattern of increased probability of an accident the greater the hours of duty time for pilots.". [21]

Among drivers

Many countries regulate working hours for truck drivers to reduce accidents caused by driver fatigue. The number of hours spent driving has a strong correlation to the number of fatigue-related accidents. According to numerous studies, the risk of fatigue is greatest between the hours of midnight and six in the morning, and increases with the total length of the driver's trip. [22]

Among healthcare providers

Fatigue among doctors is a recognized problem. It can impair performance, causing harm to patients. A study using anonymous surveys completed by junior doctors in New Zealand found that 30% of respondents scored as "excessively sleepy" on the Epworth Sleepiness Scale and 42% could recall a fatigue-related clinical error in the past six months. [23]

In the US, shift length is limited for nurses by federal regulation and some state laws. [24]

On ships

Fatigue on board is still a major factor of accidents which lead to casualties, damage and pollution. Studies show that most accidents happen during the night [25] especially around 4 am due to the Circadian rhythm of humans . [10] Studies like Project Horizon [26] have recently been done to analyse which factors cause this fatigue. The lack of sleep and quality of the sleep are two of the main issues. The lack of sleep is due to the long hours that the workers (especially the Officers) have to do (work weeks of 70 hours +). [27] After that there is the quality of their sleep which is affected by a variety of factors. [26] There will be the quality of the food on board, the vibrations due to the engine and waves, the noise of repair or works or engine, only naps (not sleeping eight hours in a single run but two or three naps a day) because of the watch system and secondary jobs. Stress on board especially when arriving in port when all hands have to be on deck whatever the time.

With companies trying to reduce the costs there is less crew. Turn around in port have to be as fast as possible because the time spent in ports is very expensive. All of this adds work and stress to the crew on board which drains them of their energy which will lead to errors due to fatigue. The ILO have conventions for trying to restrict the maximum working hours on board and to determine the minimum rest period of seafarers. [27] Unfortunately, the maritime industry is so competitive and there are fewer and fewer crew members on board that it makes it difficult to not work overtime; otherwise the workers will fall behind on their work load. [28]

See also

Related Research Articles

Jet lag is a physiological condition that results from alterations to the body's circadian rhythms caused by rapid long-distance trans-meridian travel. For example, someone flying from New York to London, i.e. from west to east, feels as if the time were five hours earlier than local time, and someone travelling from London to New York, i.e. from east to west, feels as if the time were five hours later than local time. The phase shift when traveling from east to west is referred to as phase-delay of the circadian circle, whereas going west to east is phase-advance of the circadian circle. Most travelers find that it is harder to timezone adjust when traveling to the east. Jet lag was previously classified as one of the circadian rhythm sleep disorders.

Delayed sleep phase disorder Chronic mismatch between a persons normal daily rhythm, compared to other people and societal norms

Delayed sleep phase disorder (DSPD), more often known as delayed sleep phase syndrome and also as delayed sleep–wake phase disorder, is a chronic dysregulation of a person's circadian rhythm, compared to those of the general population and societal norms. The disorder affects the timing of sleep, peak period of alertness, the core body temperature, rhythm, hormonal as well as other daily cycles. People with DSPD generally fall asleep some hours after midnight and have difficulty waking up in the morning. People with DSPD probably have a circadian period significantly longer than 24 hours. Depending on the severity, the symptoms can be managed to a greater or lesser degree, but no cure is known, and research suggests a genetic origin for the disorder.

Advanced Sleep Phase Disorder (ASPD), also known as the advanced sleep-phase type (ASPT) of circadian rhythm sleep disorder, is a condition that is characterized by a recurrent pattern of early evening sleepiness and early morning awakening. This sleep phase advancement can interfere with daily social and work schedules, and results in shortened sleep duration and excessive daytime sleepiness. The timing of sleep and melatonin levels are regulated by the body's central circadian clock, which is located in the suprachiasmatic nucleus in the hypothalamus.

Fatigue Range of afflictions, usually associated with physical and/or mental weakness

Fatigue is a feeling of tiredness. It may be sudden or gradual in onset. It is a normal phenomenon if it follows prolonged physical or mental activity, and resolves completely with rest. However, it may be a symptom of a medical condition if it is prolonged, severe, progressive, or occurs without provocation.

A microsleep (MS) is a sudden temporary episode of sleep or drowsiness which may last for a few seconds or up to several seconds where an individual fails to respond to some arbitrary sensory input and becomes unconscious. MSs occur when an individual loses and regains awareness after a brief lapse in consciousness, often without warning, or when there are sudden shifts between states of wakefulness and sleep. In behavioural terms, MSs may manifest as droopy eyes, slow eyelid-closure, and head nodding. In electrical terms, microsleeps are often classified as a shift in electroencephalography (EEG) during which 4–7 Hz activity replaces the waking 8–13 Hz background rhythm.

Shift work is an employment practice designed to make use of, or provide service across, all 24 hours of the clock each day of the week. The practice typically sees the day divided into shifts, set periods of time during which different groups of workers perform their duties. The term "shift work" includes both long-term night shifts and work schedules in which employees change or rotate shifts.

Non-24-hour sleep–wake disorder is one of several chronic circadian rhythm sleep disorders (CRSDs). It is defined as a "chronic steady pattern comprising [...] daily delays in sleep onset and wake times in an individual living in a society". Symptoms result when the non-entrained (free-running) endogenous circadian rhythm drifts out of alignment with the light–dark cycle in nature. Although this sleep disorder is more common in blind people, affecting up to 70% of the totally blind, it can also affect sighted people. Non-24 may also be comorbid with bipolar disorder, depression, and traumatic brain injury. The American Academy of Sleep Medicine (AASM) has provided CRSD guidelines since 2007 with the latest update released in 2015.

Shift work sleep disorder (SWSD) is a circadian rhythm sleep disorder characterized by insomnia, excessive sleepiness, or both affecting people whose work hours overlap with the typical sleep period. Insomnia can be the difficulty to fall asleep or to wake up before the individual has slept enough. About 20% of the working population participates in shift work. SWSD commonly goes undiagnosed, so it's estimated that 10–40% of shift workers suffer from SWSD. The excessive sleepiness appears when the individual has to be productive, awake and alert. Both symptoms are predominant in SWSD. There are numerous shift work schedules, and they may be permanent, intermittent, or rotating; consequently, the manifestations of SWSD are quite variable. Most people with different schedules than the ordinary one might have these symptoms but the difference is that SWSD is continual, long-term, and starts to interfere with the individual's life.

Sleep-deprived driving is the operation of a motor vehicle while being cognitively impaired by a lack of sleep. Sleep deprivation is a major cause of motor vehicle accidents, and it can impair the human brain as much as inebriation can. According to a 1998 survey, 23% of adults have fallen asleep while driving. According to the United States Department of Transportation, male drivers admit to have fallen asleep while driving twice as much as female drivers.

Hours of service U.S. commercial motor vehicle driver working and rest period restrictions

Hours of Service (HOS) regulations are issued by the Federal Motor Carrier Safety Administration (FMCSA) and govern the working hours of anyone operating a commercial motor vehicle (CMV) in the United States. These regulations apply to truck drivers, commercial and intercity bus drivers, and school bus drivers who operate CMVs. These rules limit the number of daily and weekly hours spent driving and working, and regulate the minimum amount of time drivers must spend resting between driving shifts. For intrastate commerce, the respective state's regulations apply.

Sleep deprivation, also known as sleep insufficiency or sleeplessness, is the condition of not having adequate duration and/or quality of sleep to support decent alertness, performance, and health. It can be either chronic or acute and may vary widely in severity.

Fatigue is a major human factors issue in aviation safety. The Fatigue Avoidance Scheduling Tool (FAST) was developed by the United States Air Force in 2000–2001 to address the problem of aircrew fatigue in aircrew flight scheduling. FAST is a Windows program that allows scientists, planners and schedulers to quantify the effects of various work-rest schedules on human performance. It allows work and sleep data entry in graphic, symbolic (grid) and text formats. The graphic input-output display shows cognitive performance effectiveness as a function of time. An upper green area on the graph ends at the time for normal sleep, 90% effectiveness. The goal of the planner or scheduler is to keep performance effectiveness at or above 90% by manipulating the timing and lengths of work and rest periods. A work schedule is entered as red bands on the time line. Sleep periods are entered as blue bands across the time line, below the red bands.

In chronobiology, a circasemidian rhythm is a physiological arousal cycle that peaks twice in a 24-hour day. Numerous studies have demonstrated that human circadian rhythms in many measures of performance and physiological activity have a 2-peak daily (circasemidian) pattern. The word, circasemidian, is based upon the Latin words circa ("about"), semi ("half") and dia ("day"). Thus, this is a rhythm that has two cycles per day, and some investigators have referred to it as the semicircadian rhythm. It usually serves to (1) deepen the pre-dawn nadir in body temperature and cognitive performance, (2) create a flat spot during the early afternoon in the daytime increase in body temperature and cognitive performance, and (3) heighten the early-evening peak in body temperature and cognitive performance. Broughton was the first to bring this characteristic of human performance to the attention of researchers.

Charles Czeisler

Charles A. Czeisler is an American physician and sleep researcher. He is a researcher and author in the fields of both circadian rhythms and sleep medicine.

Fatigue detection software is intended to reduce fatigue related fatalities and incidents. Several companies are working on a technology for use in industries such as mining, road- and rail haulage and aviation. The technology may soon find wider applications in industries such as health care and education.

Studies, which include laboratory investigations and field evaluations of population groups that are analogous to astronauts, provide compelling evidence that working long shifts for extended periods of time contributes to sleep deprivation and can cause performance decrements, health problems, and other detrimental consequences, including accidents, that can affect both the worker and others.

Sleep in space Sleep in an unusual place

Sleeping in space is an important part of space medicine and mission planning, with impacts on the health, capabilities and morale of astronauts.

Pilot fatigue

The International Civil Aviation Organization (ICAO) defines fatigue as "A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload." The phenomenon places great risk on the crew and passengers of an airplane because it significantly increases the chance of pilot error. Fatigue is particularly prevalent among pilots because of "unpredictable work hours, long duty periods, circadian disruption, and insufficient sleep". These factors can occur together to produce a combination of sleep deprivation, circadian rhythm effects, and 'time-on task' fatigue. Regulators attempt to mitigate fatigue by limiting the number of hours pilots are allowed to fly over varying periods of time.

Sleep deprivation in higher education

Sleep deprivation - the condition of not having enough sleep - is a common health issue for students in higher education. This issue has several underlying and negative consequences, but there are a few helpful improvements that students can make to reduce its frequency and severity. On average, university students get 6 to 6.9 hours of sleep every night. Based on the Treatment for Sleep Disorders, the recommended amount of sleep needed for college students is around 8 hours. According to Stanford University's Department for the Diagnosis, 68% of college students aren't getting the sleep they need. The main causes of sleep deprivation include poor sleep hygiene, biology, use of technology, and use of drugs. The effects can damage the student’s GPA, as well as negatively affect the student's focus and memory. Furthermore, the effects on the individual’s mental health can be harmful too. Students may face depression, anxiety, and difficulty maintaining their relationships. There are many possible solutions to combat sleep deprivation including improving bedroom environment, reducing exposure to blue light, and taking naps during the day.

Dr. Debra J. Skene is a chronobiologist with specific interest in the mammalian circadian rhythm and the consequences of disturbing the circadian system. She is also interested in finding their potential treatments for people who suffer from circadian misalignment. Skene and her team of researchers tackle these questions using animal models, clinical trials, and most recently, liquid chromatography-mass spectrometry. Most notably, Skene is credited for her evidence of a novel photopigment in humans, later discovered to be melanopsin. She was also involved in discovering links between human PER3 genotype and an extremely shifted sleep schedules categorized as extreme diurnal preference. Skene received her Bachelor of Pharmacy, Master of Science, and Ph.D. in South Africa.

References

  1. 1 2 3 4 "Regulatory Impact and Small Business Analysis for Hours of Service Options". Federal Motor Carrier Safety Administration. Archived from the original on 26 January 2008. Retrieved 22 February 2008.
  2. ↑ "CDC Features - Drowsy Driving: Asleep at the Wheel". www.cdc.gov. Retrieved 13 October 2015.
  3. ↑ Gandevia SC (1992). "Some central and peripheral factors affecting human motoneuronal output in neuromuscular fatigue". Sports Medicine. 13 (2): 93–8. doi:10.2165/00007256-199213020-00004. PMID   1561512. S2CID   20473830.
  4. ↑ Hagberg M (1981). "Muscular endurance and surface electromyogram in isometric and dynamic exercise". Journal of Applied Physiology. 51 (1): 1–7. doi:10.1152/jappl.1981.51.1.1. PMID   7263402.
  5. ↑ Hawley JA, Reilly T (1997). "Fatigue revisited". Journal of Sports Sciences. 15 (3): 245–6. doi:10.1080/026404197367245. PMID   9232549.
  6. ↑ "Mental Fatigue". 5 October 2007.
  7. ↑ "Melatonin". University of Maryland Medical Center. Retrieved 24 April 2008.
  8. ↑ Czeisler, Charles A. "Pathophysiology and Treatment of Circadian Rhythm Sleep Disorders". [Insomnia and Beyond: The Neurochemical Basis for Targeted Sleep Therapeutics]. Medscape. Retrieved 24 April 2008.
  9. ↑ Van Dongen HP, Caldwell JA, Caldwell JL (May 2006). "Investigating systematic individual differences in sleep-deprived performance on a high-fidelity flight simulator". Behav Res Methods. 38 (2): 333–43. doi: 10.3758/BF03192785 . PMID   16956110.
  10. 1 2 Van Dongen HP (2006). "Shift work and inter-individual differences in sleep and sleepiness". Chronobiol. Int. 23 (6): 1139–47. doi:10.1080/07420520601100971. PMID   17190701.
  11. ↑ Millar, Michelle (2012). "Measuring Fatigue" (PDF). ICAO.int. ICAO/IATA/IFALPA. p. 8.
  12. ↑ Wickens, C. D.; Lee, J. D.; Gordon, S. E.; Liu, Y. (2003). An introduction to human factors engineering. New York: Longman.
  13. ↑ NASA report to Congress on fatigue, http://comair-5191.com/NASA%20Statement%20on%20Pilot%20Fatigue.pdf Archived 2 October 2008 at the Wayback Machine
  14. ↑ Caldwell, J.A., Mallis, M.M., Caldwell, J.L., Paul, M.A., Miller, J.C., & Neri,mD.F. Fatigue Countermeasures in Aviation Archived 7 October 2015 at the Wayback Machine . Aviation, Space, and Environmental Medicine, 80(1), 29-59.
  15. ↑ Levin, ALan (10 April 2007). "NTSB: Fatigue threatens air safety". USA Today . Retrieved 22 December 2018.
  16. ↑ Fatigue and Aviation Safety
  17. ↑ Events which include fatigue as a contributory factor on SKYbrary
  18. ↑ FAA's ASAP Program, https://www.faa.gov/about/initiatives/asap/
  19. ↑ NTSB Most Wanted List, fatigue, https://www.ntsb.gov/Recs/mostwanted/aviation_reduce_acc_inc_humanfatig.htm
  20. ↑ Akerstedt, T.; Mollard, R.; Samel, A; Simons, M.; Spencer, M. (2003). Paper prepared for the ETSC "Meeting to discuss the role of EU FTL legislation in reducing cumulative fatigue in civil aviation" in Brussels on Wednesday 19th February 2003 (PDF) (Report). European Transport Safety Council.
  21. ↑ Goode, Jeffrey H. (August 2003). "Are pilots at risk of accidents due to fatigue?" (PDF). Journal of Safety Research. 34 (3): 309–313. doi:10.1016/S0022-4375(03)00033-1. PMID   12963077.
  22. ↑ "Hours of Service of Drivers; Driver Rest and Sleep for Safe Operations; Proposed Rule". Federal Motor Carrier Safety Administration. Archived from the original on 1 October 2006. Retrieved 16 February 2008.
  23. ↑ Gander, P.; Purnell, H.; Garden, A.; Woodward, A. (2007). "Work patterns and fatigue-related risk among junior doctors". Occupational and Environmental Medicine. 64 (11): 733–738. doi:10.1136/oem.2006.030916. PMC   2078416 . PMID   17387138.
  24. ↑ "Safety and Health Topics | Long Work Hours, Extended or Irregular Shifts, and Worker Fatigue - Limitations on Work Hours | Occupational Safety and Health Administration". osha.gov. Retrieved 12 August 2018.
  25. ↑ "Safety Digest" (PDF). Marine Accident Investigation Branch (MAIB). February 2004.
  26. 1 2 Leeuwen, Wessel M.A. Van (2012). "Final report project HORIZON". ResearchGate. doi:10.13140/rg.2.1.4844.7127 . Retrieved 18 November 2018.
  27. 1 2 "Convention C109 - Wages, Hours of Work and Manning (Sea) Convention (Revised), 1958 (No. 109)". www.ilo.org. Retrieved 29 November 2018.
  28. ↑ "Guidelines for the Development of Tables of Seafarers' Shipboard Working Arrangements and Formats of Records of Seafarers' Hours of Work or Hours of Rest" (PDF). IMO. 29 November 2018.
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