PVTs in outer space: challenges to astronaut sleep and alertness

By Dr. Stijn Massar

Did you know that the PVT tasks you are doing are the same as those used to monitor astronaut alertness? The Psychomotor Vigilance Task (PVT) was developed by Prof David Dinges at the University of Pennsylvania in 1985. While the test is deceptively simple – just press a button when the timer appears, right? – it is actually an extremely powerful tool. The fact that is simple, and even rather boring, makes it is highly sensitive to changes in alertness due to sleep and circadian disturbances.

Since the early years, the PVT has been deployed in situations where high performance is required under extreme circumstances. In aviation, deep sea expeditions, and on military missions, duty schedules are often highly demanding and not in line with one’s natural sleep rhythms or with the external day-night cues. Yet, alertness is often critical for successful operations.

Space missions are no exception to these challenges. Astronauts sleep under microgravity, with no clear distinction between what is lying down or what is standing up. Besides that, external time cues are completely out of whack. While orbiting the earth in the International Space Station, the sun rises and sets every 90 minutes. That is akin to experiencing jet lag 16 times a day! Sleeping under these circumstances can be extremely challenging.

Read about the challenges to sleep on space missions: Why scheduling naps is one of NASA’s most important jobs - The Washington Post

The PVT has been used to monitor astronaut alertness in training and simulations for a long time. In 2009, the PVT was launched into space for the first time on the International Space Station 21-22 mission. Astronauts who stayed on the ISS for 6 months performed the PVT twice daily, as well as at the base before and after deployment. Ever since, the PVT has been used regularly on the ISS. As communication between the space station and ground control can be delayed, the reaction time feedback delivered by the PVT can help astronauts to self-assess whether they are fit for duty at any given moment (hence it was renamed the Reaction Self Test).

Optimizing sleep and alertness on rotating shift schedules can be challenging in space and on earth alike. By doing the PVTs, we hope to contribute to understanding the impact of call schedules on your mission as a healthcare professional.

Listen to an interview with Prof Dinges on the use of the PVT in space missions: Space Station Live: Reaction Self Test - YouTube

Commander Jeffrey Williams demonstrating the PVT onboard the ISS Expedition 22 (2010)