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, reported