· Log in

Shift Work Disorder in Astronauts – Study Shows Flexibility

Written by: SFD News on September 15th, 2009

Shift Work Disorder in Astronauts - Study Shows Flexibility | read this item

Researchers from Brigham and Women’s Hospital’s (BWH) Division of Sleep Medicine successfully have shown flexibility within the Human Biological Clock when they synchronized individuals to a light/dark cycle that correctly aligned their biological clock to the 24.65-hour day of the planet Mars and to the 23.5-hour day often experienced by astronauts flying in low orbit.

Shift work disorder is a common Circadian rhythm sleep disorder and would probably be experienced by Astronauts visiting Mars.

In this study, seven healthy young men lived in a personal laboratory room free of time cues for 73 days. Prior to the study, the men maintained a regular 8-hour sleep/16-hour wake schedule for three weeks at home, and did not take medications and/or drugs the week before or during the study.

During the study, ambient light and room temperature were controlled and sleep opportunities were scheduled. Subjects lived on the Martian day and the 23.5-hour day, alternately for two-week intervals. During this time, Scheer and colleagues tested whether the experimental light conditions could synchronize the biological clock of the subjects to the non-24-hour sleep/wake cycles.

Following each two-week session, the researchers tested whether an individual’s circadian period showed longer-term changes that outlived the light/dark cycles – whether the period was lengthened or shortened – by measuring the intrinsic period of rhythms of core body temperature and the hormones melatonin and cortisol.

The researchers found that exposure to moderately bright light for the second or first half of the scheduled wake period was effective for entraining individuals’ biological clocks to the 24.65-hour Martian day or to the 23.5-hour day, respectively.