A NASA-funded Pitt team is exploring the benefits of sleeping in space

Long-duration spaceflight promises to be boring — yet dangerous. Although humanity doesn’t have such plans yet, thinking about these problems will not only help once we head further into space, they can also help patients here on Terra Firma. One potential way to ease some burdens of long-duration spaceflight would be to reduce an astronaut’s metabolic rate, like hibernating animals.

Kate Flickinger, principal physiologist of the Applied Physiology Lab in Pitt’s Department of Emergency Medicine and a researcher studying how lower metabolic rates would affect astronauts’ muscular and skeletal health, has been selected as a Translational Research Institute for Space Health (TRISH) fellow.

Psychological stress aside, long duration spaceflight risks exposure to radiation, vision loss, reduced bone density and muscle atrophy.  “They’re not going to have all of the exercise equipment that they have on the International Space Station,” said Katie Flickinger. “But if you get to Mars and your body is Jello and you can’t even get out of the spacecraft, then the mission is a failure.”

Flickinger began looking into the topic in 2012 while she was working on a project in the lab of her mentor, Clifton Callaway, executive vice chair of emergency medicine and the Ronald D. Stewart Endowed Chair of Emergency Medicine Research.

The Callaway lab had a history of research into lowering temperature and metabolic rate, particularly for people who had a brain injury after cardiac arrest.

“If you lower their core body temperature, it improves neurologic outcomes and chances of survival,” Flickinger said. “We thought, ‘what if we can cool other populations?’”

So, when TRISH put out a call for research into metabolic manipulation, the Flickinger and her team jumped at the chance. Support from TRISH, a NASA-funded consortium led by Baylor College of Medicine in partnership with several other institutions, allowed the researchers to get imaginative when considering other contexts in which lower metabolism could be of use.

“All of us in the department are pretty big space fans,” Flickinger said, “We had daydreamed about this for years in the lab.”

To be clear, she said, “we are nowhere near allowing individuals to hibernate like bears for months on end.” But when bears do hibernate, they don’t lose bone mass or mineral density, whereas ICU patients do. Those are the mechanisms into which Flickinger and her team — Clif Callaway; Frank Guyette, professor of emergency medicine; Alexandra Weisman, assistant professor of emergency medicine; Philip Empey, associate professor of pharmacy; Daniel Buysse, Distinguished Professor of Psychiatry; Benjamin Gordon, assistant professor of health and human development in the School of Education; and external collaborators Marie Mortreux and Kathleen Melanson in the department of nutrition at the University of Rhode Island — are looking.

The TRISH-funded research involves putting volunteers to sleep using a mild sedative. After 20 hours, the volunteers are roused and fed. They’re taken through cognitive testing and an exercise regimen, and then they get some “time to be human,” Flickinger said. They can stretch, shower and make phone calls — then it’s back to sleep for another 20 hours. They do this five times in a row.

The research team is measuring muscle type and muscle health and looking for signs of inflammation throughout the experiment. They will also use several measures to determine the volunteers’ metabolic rate and look for any correlations between metabolism and body temperature.

“As an exercise physiologist, this goes against everything that I have been taught,” Flickinger said. “Usually, I want to increase muscle mass, I want to increase aerobic capacity.” But the goal of this research is for people to remain stable.

Improved musculature might sound good, but in the case of space travel, increased energy demands of building muscle would create problems. A lower metabolic rate means people need less oxygen; in space that also means CO2 scrubbers don’t have to work as hard. Astronauts would need less food, and the perceived duration of the trip would be much shorter, a psychological benefit. “Less time to think, ‘Oh, I’m trapped in a tin can without much to do.’” Flickinger said.

Back on earth, the team’s findings can be used to support critically ill patients. “Sitting in the ICU, sometimes patients can lose up to 30% or more of their muscle mass,” Flickinger said. “If we can reduce their metabolism, maybe we can spare their muscle mass as well.”

Photography courtesy of Katie Flickinger