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​U.S.-Russian Team Examines Human Internal Clock Aboard The MIR Space Station

PITTSBURGH, February 10, 1997 — Using a U.S. astronaut and two Russian cosmonauts aboard the Russian space station Mir as "lab assistants and study volunteers," a team of scientists from the United States and Russia, led by a University of Pittsburgh Medical Center (UPMC) researcher, will determine how microgravity and long absences from natural day-night time cues affect the human body. The study will begin Feb. 13, after two Russian cosmonauts join American astronaut Jerry Linenger aboard the space station.

Timothy Monk, Ph.D., professor of psychiatry at the UPMC's Western Psychiatric Institute and Clinic (WPIC), and Russian co-investigators Irina Ponomareva, Cand.Sci., and Irina Larina, Cand.Sci., of the Institute for Biomedical Problems in Moscow, will look at changes in performance, mood and sleep based on the astronauts' circadian rhythms. Their research is an extension of previous studies done during a mission of the Space Shuttle Columbia from June 20 through July 7, 1996.

Circadian rhythms serve as the body's 24-hour "internal clock," and prepare the mind for restful sleep at night and active wakefulness during the day. To accomplish this, various hormones, such as melatonin, and vital signs, like body temperature, fluctuate on a regular basis, creating "troughs" and "peaks." Many rhythms trough early in the morning, when people are asleep, and peak during the day, when most people are active. Without circadian rhythms, the body and mind would have no internal means of regulating cycles of activity and rest.

On Earth, day and night act as time cues to reset human circadian rhythms to a 24-hour cycle each day. Scientists have discovered that when people are kept away from these natural cues, their circadian rhythms "free-run" at slightly more than 24 hours. These free-running rhythms result in bouts of less consolidated and lighter sleep. When microgravity -- the weightlessness astronauts experience when in Earth's orbit -- is added to this equation, circadian rhythms may be thrown off even more.

"We plan to see how free-running circadian rhythms might affect astronauts as they go about their daily business," Dr. Monk explains. "On earth, we see similar behavior in shift workers, and to a lesser extent, people with jet lag. What is not yet clear is how free-running circadian rhythms impact a person's sleep and alertness over the long term. Now, we'll have the chance to find out the degree to which this problem might affect astronauts and cosmonauts on long-duration space missions."

The National Aeronautics and Space Administration (NASA) will use the studies to help determine if creating artificial days and nights would be beneficial to astronauts, or if certain work/rest schedules should be developed.

"The natural balances our bodies maintain are linked to productivity, safety and general well-being," Dr. Monk says. "What we learn can have a tremendous impact, not just on astronauts, but on the thousands of people whose jobs require them to work varying shifts."

Much of the information used to develop this latest study was obtained last July, when Dr. Monk and other scientists from WPIC examined astronauts during the 17-day shuttle Columbia mission that was the first ever to simultaneously look at sleep, circadian rhythms and work performance in space. While the average length of a shuttle mission is fewer than 20 days, the crew members on the Mir space station will stay aloft for about 120 days each at staggered intervals. Measurements will take place in three 12-day blocks to occur in the beginning, middle and end of their mission, with the final study of this series being completed on July 10. A different crew will continue the study later in 1997. Linenger is aboard Mir now, and the Russian crew is expected to launch on Feb. 10.

The crew members will use a laptop computer which has all of the sleep diaries and mood and performance tests loaded into it. All of the software being used in this experiment was developed at WPIC. Programmer Tim Hoffman worked with the Russian co-investigators and interpreters to develop Russian versions of each application. Kathy Kennedy, the study's project administrator, trained Linenger and the Russian cosmonauts to use the programs.

"Before we can think about sending people on long missions in space, such as a manned trip to Mars, we need to find out what we can do to keep astronauts' internal clocks from going out of synchrony," Dr. Monk stresses. "Further, what we learn from these experiments may someday cause us to rethink the way we schedule shift workers."

For more information about psychiatry or to learn about current research studies, visit the UPMC's Western Psychiatric Institute and Clinic Web site.

 

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