Sleep is a basic human need like eating, drinking and breathing and is vital for good health and well-being. Sleep deficiency can lead to physical and mental health problems and are linked to many chronic health problems including heart, disease, kidney disease, high blood pressure, diabetes, stroke, obesity and depression.
Sleep deficiency has also played a role in human mistakes linked to tragic accidents such as nuclear reactor meltdowns, grounding of large ships and plane crashes. It is imperative to get enough quality sleep for an individual to function well. People deprived of sleep are less productive, take longer to finish tasks, have slower reaction time and make more mistakes. (1)
In commercial aviation, fatigue is described as a physiological state of reduced mental or physical performance capability resulting from sleep loss, extended wakefulness, circadian phase and workload. Fatigue associated with sleep loss, shift work and long duty cycles cause aviators to become sloppy, inattentive, careless and inefficient and the only cure for fatigue is adequate sleep which is difficult due to work requirements, family demands and poor sleep habits.
The requirements to work a variety of schedules and work away from home are likely contributing factors to poor sleep quality. A number of personnel may be suffering from sleep deprivation due to intentional sleep restriction combined with rotating schedules and other work demands which contribute to wide-spread fatigue in the aviation community.(2)
Very few studies have been conducted to understand the sleep patterns and fatigue in aviation professionals. One such study was conducted by International Civil Aviation Organization (ICAO) which recommended fatigue risk management systems (FRMSs) to mitigate the risks associated with fatigue.
The primary fatigue mitigation strategy recommended for long haul flights is use of in-flight sleep (3)
Circadian dysregulation(jetlag), sleep loss (extended wakefulness), sleep deprivation (acute or chronic), fatigue (exhaustion), pre-existing medical conditions and use of medication can all be contributing factors for commercial aircraft pilots sleep irregularities and sleep deprivation. A study was conducted to examine Airbus A320 pilots and co-pilots for one of Saudi Arabia's commercial airline. (4)
It was identified that healthy pilots are at risk of poor sleep quality and irregular sleep patterns. The study considered 24 participants that showed 66.7% had a irregular sleep pattern, 41.7% of all participants had poor sleep efficiency, 18 participants had poor sleep quality. The frequencies of sleepiness was 12.5% and fatigue was 29.2%. there was no correlation between different demographic parameters like age, work experience, typical duty times, BMI and sleep disturbances, there was a moderate correlation between years of work experience and time spent in bed (r= -0.524 ; p=0.009), yet there was no difference in sleep time and sleep efficiency for more experienced pilots. The study also showed significant negative correlation between number of T/O and landings per month and sleepiness measured by the ESS (Epworth Sleepiness Scale).
In another study conducted by Brazilian airline, it was observed that main factors associated with increased fatigue as reported by the pilots were long working hours, flight hours, little rest time between working hours and night work as highlighted in below graph (5)
The study included 1234 pilots out of which pilots percentage of smokers was low at 7%, percentage of pilots reporting drinking alcohol was 75% which included low-risk use reported by 75.2%, moderate use by 23.6% and harmful use was reported by 1.2%.
578 diseases with medical diagnosis were reported to be most prevalent diseases, injuries, musculoskeletal disorders, digestive and respiratory diseases were reported as (35.8%, 28.2%, 24.6% and 21.6% respectively). About 57.8% pilots have reported that have slept unintentionally while in command of airplane, for those who flew more than 65 hours/month showed increased 78% chance of unintentional sleep compared to pilots who flew less than 65 hours.
Introduction of ultra long-range flights (ULR) created the need for long working times. A study was performed to assess the alertness, objective attention, concentration ability with the FAIR-2 tests and 3-min psychomotor vigilance test and for statistical analysis ANOVA with a post-hoc-analysis and Wilcoxon signed-rank test were conducted on 28 flight crew members on a ULR. It was observed that subjective concentration ability declines and fatigue increased significantly over the course of the flight with no significant changes in objective concentration was observed.(6)
Pilot fatigue is a significant problem in modern aviation operations, largely because of unpredictable work hours, long duty period, circadian disruptions and insufficient sleep. The full impact of sleep deprivation and fatigue is underappreciated, but many of its deleterious effects have long been known. Compared to people who are well rested, sleep deprived people move more slowly, make more mistakes, have memory issues leading to errors and accidents.
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