New research highlights why sleep loss poses an insidious threat to flight safety

Sleep-deprived pilots suffer several impairments in mood and cognition, according to new research published in the scientific journal Biological Rhythm Research. The findings provide more evidence that sleep deprivation poses a serious threat to flight safety.

“I began by researching the effects of sleep loss on endurance cyclists. As I explored the area further, I got a greater appreciation and understanding of the effects of sleep on performance whether in a sporting, professional or personal capacity,” said study author Anna Donnla O’Hagan, a postgraduate researcher at Dublin City University.

“At the time, there was increasing concern for the impact of long working hours and extended periods of wakefulness on commercial airline pilots with a relatively limited amount of research being done in the area. I therefore decided to further investigate this area.”

In the study, 7 commercial airline pilots completed multiple rounds of testing over the course of several days. In their final testing session, the participants had been continuously awake for 24 hours.

The participants completed surveys assessing their mood along with several tests of cognitive performance. They also used a high-fidelity flight simulator, in which they were tasked with flying a holding pattern for about 30 minutes. During the simulated flights, the participants were required to conduct a fuel calculation and complete other aviation-specific mathematical calculations.

Some aspects of the pilots’ flight performance — such as their ability to maintain the proper flight path — were not significantly impaired by sleep deprivation overall.

That may sound like good news. But the researchers observed that performance on almost all the psychological measures and cognitive performance tasks were significantly affected by the lack of sleep.

“Sleep loss and fatigue pose an insidious threat to flight safety which manifests itself in different ways such as reductions in vigilance, impairments in judgments and increases in reaction times. Everyone is susceptible to the effects of sleep loss and fatigue regardless of skill, knowledge, or training,” O’Hagan told PsyPost.

Both the accuracy and speed of aviation-specific mathematical calculations started to decline after 15 hours of continuous wakefulness. There was only one exception: the accuracy of fuel calculations was not significantly impaired.

As they became more sleep deprived, the pilots also had a harder time answering mid-flight situational awareness questions. Loss of situational awareness is a frequent cause of accidents.

“The number of serious accidents as a result of operator error in various industries due to sleep loss and fatigue is large and appears to be increasing,” O’Hagan said.

“Enhancing our understanding and identifying and mitigating sleep deprivation and fatigue among operators through implementation of safe and effective working regulations and real-time indicators of working performance will aid in promoting health and safety.”

The new research adds to a growing body of evidence that indicates sleep deprivation harms aviation performance and compromises safety. For instance, in another study, 10 current and qualified F-117 pilots were deprived of one night of sleep and then were tested on precision instruments. Despite their experience and training, the pilots suffered a “clear-cut loss of basic flight control skill.”

“Loss of sleep is a common occurrence in modern civilisation. Humans are the only animals who opt to achieve less sleep than is required by their biological clocks and their sleep needs. In today’s society and culture, sleep loss is considered a norm as opposed to an exception with value placed on the attempt to reduce sleep time,” O’Hagan told PsyPost.

“The notion prevails that loss of sleep is not important and can be overcome by force of will. However, these inferences are unsafe and perilous with loss of sleep found to significantly impair behavioural, physiological and neurocognitive functioning and as a result, negatively impact performance. It is vital that sleep loss is further explored and understood to promote and enhance safety and well-being.”

The study, “Flying on empty – effects of sleep deprivation on pilot performance“, was authored by Anna Donnla O’Hagan, Johann Issartel, Aidan Wall, Friedrich Dunne, Patrick Boylan, Jaap Groeneweg, Matthew Herring, Mark Campbell, and Giles Warrington.