Initial results from a study of Chris Hadfield and other astronauts who spent months aboard the International Space Station have turned up changes like those seen in someone developing Type 2 diabetes on Earth.
The results, to be presented at an international meeting in Waterloo, Ont., on Tuesday, are evidence for yet another deleterious effect of spaceflight that could impact long-duration voyages, such as a trip to Mars. It also demonstrates the close parallels between life in space and a sedentary lifestyle in Canada and elsewhere, where diabetes has become a growing problem for an inactive population.
"Is it a surprise? Not completely," said Richard Hughson, director of the University of Waterloo lab that led the study. In the confined, zero-g environment of the space station, astronauts experience almost none of the daily physical demands required by normal life on the ground. "They are the most sedentary working population that you can find."
He and his team observed elevated levels of insulin and other related blood factors in four astronauts, though none has diabetes symptoms. They are now busy testing blood samples gathered from five other astronauts. Those samples were returned to Earth just three weeks ago.
The preliminary finding suggests that an increase in blood sugar due to inactivity could play a role in stiffening arteries, another change Prof. Hughson has been studying. He has now applied to do a followup study to explore the connection and see if astronauts shed the diabetes-like indicators they've acquired after they've spent time back on Earth.
Prof. Hughson's findings are part of a special one-day symposium during the meeting that will explore how living in space is like an accelerated form of aging.
"In a month of spaceflight you see about the same change in bone that you see in a year in a postmenopausal woman," said Scott Smith, manager for nutritional biochemistry at NASA's Johnson Space Center in Houston. "It's like doing time-lapse photography."
Martina Heer, a professor in nutrition physiology at the University of Bonn and a meeting co-chair, said astronaut studies can shed light on aspects of aging that are hard to disentangle in a heterogeneous elderly population and also aid in the quest for countermeasures that would help people age in a healthier way.
Other new findings that will be presented at the symposium include an MRI study of a group of German researchers who spent more than a year at the South Pole on a research trip. The study showed that after a year of isolation and confinement, they experienced shrinkage in brain regions related to working memory and decision-making and a marked decrease in a neurological factor known as BDNF. "These data are very much in line with what you see in patients with dementia," said study leader Alexander Stahn of the Center for Space Medicine in Berlin.
During a session on Monday, Canadian astronaut Robert Thirsk described an unexpected problem he and another crew member experienced: They found themselves becoming farsighted while on board the space station in 2009. They conducted ultrasound exams on each other's eyes while NASA sent up glasses so they could continue to perform their tasks.
The problem, related to a swelling of optic nerves, is now thought to affect about 20 per cent of astronauts. Dr. Smith has been studying a possible genetic link that may indicate susceptibility to the condition.
The experience offers a caution that some effects of spaceflight on the human body may still be undiscovered, said Dr. Thirsk, who is set to become chancellor at the University of Calgary on July 1. "The lesson is, whenever we push the envelope in terms of human activity in space, we're going to encounter a new medical challenge that's out there."
The meeting, hosted in Canada for the first time, has drawn about 150 experts in gravitational physiology from North America, Europe and Japan.