Details on Space Aging Informs Health Research

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While paging through the book Space Physiology and Medicine in 1995, Senator John Glenn spotted a chart that captured his imagination. Listed were 52 kinds of physical changes routinely experienced in space by orbiting astronauts, including osteoporosis, cardiovascular difficulties and alterations in the distribution of body fluids. Th e 73-year-old Glenn, who had spent years on the Senate Special Committee on Aging, realized that he was looking at a list of complaints common to seniors — yet the typical astronaut was in their 30s, 40s or 50s.

Given the similarities, Glenn wondered if there were any plans to fly senior citizens into space. He called the authors of the publication along with other space doctors to find out. To his surprise, despite shuttle missions going up every few months, nobody knew of any plans to send an elderly person into orbit. “I wondered why the science had to wait,” Glenn wrote in his autobiography. “Shuttle flights were going up regularly. Why couldn’t room be made on one of them for some experiments on senior citizens? And then I began to think, ‘Why not me?’”

Early in his career, Glenn trained as a Marine and was an accomplished test pilot, breaking numerous flying records before being scooped up by NASA in the very first astronaut recruitment drive. Famous for his clean-cut image and charm, he was a favorite to be the first to fly in space. Indeed, he was on NASA’s first orbital mission, Friendship 7, in 1962. But his plans for a return to space were stymied by the Kennedy administration, which deemed Glenn too valuable a national hero for such a trip. So, Glenn left NASA and moved into politics, never expecting that the chance for space travel would come up again.

Several things played into Glenn’s favor as he lobbied NASA in 1995 for a flight opportunity. The agency was, of course, wary of sending a senior into space — let alone one as famous as Glenn, a politician for decades.

Yet NASA did have 42 years of data on the astronaut, who had consented to regular medical checks under an agency program for retired astronauts. Glenn was also in remarkably good health, with one Washington Post report describing him as “one very fit, lifelong jet jockey who power-walks two miles a day on Earth and has passed all his preflight physical tests.”

Glenn told NASA that this was not simply a bid to get himself one last joyride in space. Th ere has always been a relationship between studies on Earth and those in space, with terrestrial research helping humans travel farther and stay longer in orbit while space research transforms the way we live on the ground. In 1997, pointing out that many countries were wrestling with the issue of caring for their aging populations, Glenn’s hope was that the spaceflight would have “enormous benefit for — well, the graying of nations, they call it, all over the world.”

Microgravity — a near absence of gravity while in orbit — temporarily induces many of the effects of aging even in younger crew members, though it appears these effects are largely reversible over time once the astronaut reaches the ground. Now, an exciting new area of investigation into this apparent accelerated aging, its underlying mechanisms and possible preventive strategies could help both astronauts and seniors improve their resilience and decrease the risk of disease.

Among the scientists conducting this research is Richard Hughson, the research chair in vascular aging and brain health at the Schlegel–University of Waterloo Research Institute for Aging in Ontario. Since 2007, Hughson has spearheaded a series of four Canadian experiments to investigate in detail why astronauts age rapidly in space, and what countermeasures can be put in place to prevent and reverse this sudden aging. He has found that “during a six-month space mission, an astronaut’s cardiovascular system can age by up to 10 or 20 years.”

The first study, which ran from 2007 to 2010, examined how the hearts and blood vessels of astronauts alter due to spaceflight. It followed six astronauts who strapped on devices that examined their heart rate, blood pressure and physical activity in several 24-hour periods before, during and after their mission. This allowed the investigation team to see how their systems changed in space and how exercise and other countermeasures — for example, wearing devices to adjust blood flow — would be helpful.

The success of this study then spurred the Vascular Series, which comprises three sets of experiments to date. The first, Vascular, looked at changes in the blood vessels and the heart over time, specifically examining how arteries change and stiffen as blood pressure alters due to less physical activity in space. Artery stiffening then came under even more scrutiny in Vascular Echo, which required astronauts to wear a leg cuff that shifted blood from the upper body to the lower body, better mimicking proper blood flow on Earth. Vascular Echo additionally monitored astronauts for a year postflight to investigate how the body readjusts after a long duration stay on the space station.

The latest in the series, Vascular Aging, looks at how and when insulin resistance may happen during a space mission. It also examines how radiation exposure may affect cardiovascular health and, like Vascular Echo, explores how well an astronaut recovers after coming back to Earth. Vascular Aging began collecting data in 2019 and will finish in 2024, according to the Canadian Space Agency.

So far, the preliminary results from Vascular show that arteries of astronauts tend to stiffen by 17 to 30 percent. Astronauts may also be at increased risk of Type 2 diabetes because they develop insulin resistance and have difficulties processing glucose. “We are seeing astronauts coming back from space with carotid arteries that have aged the equivalent to 20 to 30 years in stiff ness,” Hughson told the Canadian Institutes of Health Research in a 2015 interview about Vascular. “It is very comparable to what you would see in an aging population.”

An astronaut returning to Earth arrives much like a delicate senior who may have several health issues that prevent them from moving for long periods of time. After all, astronauts don’t work very hard to move from place to place in space. Their lungs, without proper exercise, become deconditioned. Even the soles of their feet become soft from disuse as they float around.

They’d be next to helpless upon landing on Earth without countermeasures in space, including a tailored exercise regime. The aim, for the first few months or so back on the ground, is to get the astronaut back to a typical state of middle age: able to drive, exercise, actively participate in work and home activities, and continue contributing to research and other missions at NASA.

After Christina Koch spent nearly a year in space, the agency published 10 ways in which the healthy 41-year-old might need to recover when coming back to Earth. Coming back meant, for example, that sleep would no longer be simple floating bliss, that smells would suddenly be frequent and that sensory inputs like wind on the face would suddenly happen again. Changes to weight and balance were also taken into account.

“On Earth we rely on our eyes and inner ear to maintain stability. In orbit, without gravity pulling down, the mind quickly stops listening to the inner ear. The eyes take over … we rely solely on visual cues,” Koch said in the article. “From what I’ve been told, it takes a couple days after landing for the mind to start listening again. The human body’s ability to adapt to its environment is nothing less than impressive.”

The recovery from space actually begins as astronauts dress for the ride home. Both NASA and Roscosmos the Russian space agency, use garments with lower-body compression to assist with adjusting fluid shift. NASA continually refines the design by studying test subjects following a period of bed rest and, of course, spaceflight. The agency notes that the garment also has applications for people on Earth who have a tendency to faint or experience difficulties in blood pressure.

Even before they go to space, NASA establishes a baseline for each astronaut to customize their rehabilitation program for their return. In other words, they make sure to tailor the training so that the astronaut is at a level of capability after the recovery period that is similar to their fitness before traveling to space — rather than aiming for an idealized standard that may not be fit for all bodies. The rehabilitation period is lengthy, and numerous astronauts have pointed to the need to take it easy and receive assistance from family members during this delicate time, which can last months.

“Postflight reconditioning begins on landing day, is scheduled for two hours per day, seven days a week for 45 days and is tailored to the specific needs of the astronaut,” reads a postflight reconditioning brief on NASA’s Technical Reports Server from 2011. Fortunately, the specialists assigned to help each astronaut recover have more than two decades of experience working with ISS crew and know what sorts of countermeasures are required to keep the returning space flyers safe and healthy.

For seniors, the implications cannot be clearer: There is more that must be done as people age to counter the effects of staying sedentary. Many doctors have pointed to the risk of sedentary work for industrial populations in general. But this newer research underlines the need not only for exercise, but for consistent exercise.

We have ample evidence showing how dramatically younger astronauts age in space, and the research on reversing this aging can be applied to improve the health and lives of elderly people on Earth. But space-flying seniors remain a small and select group. The eldest so far — Wally Funk, 82, and William Shatner, 90 — experienced suborbital flights of only a few minutes long in 2021. Both appeared energetic in media interviews post-landing, although detailed medical results were not disclosed.

The longest senior stint in space so far still belongs to NASA’s John Glenn, whose flight captivated the imaginations of young and old alike in 1998. At age 77, Glenn flew as a payload specialist on the STS-95 Spacehab mission, meaning he was responsible for some of the many life-science and microgravity experiments on board. All reports indicate that he was careful to contribute; a media report said he “received good reviews for his work ethic and affability” and didn’t bother himself with the attendant celebrity that his name could have brought. On board the mission, he made sure to fulfill crew responsibilities of not just experiments but also housekeeping and meal preparation.

Glenn performed several experiments on himself in space, sometimes with the assistance of fellow astronaut Scott Parazynski, a medical doctor who was on board with him. Metabolism experiments had him swallowing one kind of amino acid in pill form and another kind by injection, as proxies for hormonal changes caused by muscle atrophy or protein loss. X-ray studies recorded changes in lean body mass. Glenn also charted his sleep patterns on four nights, comparing the results of taking melatonin or placebo pills, and tracked his core body temperature with a mini thermometer embedded in a capsule he had swallowed. His brain waves were monitored using devices clamped to his scalp, wrist and chest, and — like many other astronauts — he gave samples of blood and waste for analysis.

The big questions today are which senior will be the next to participate in an extended orbital mission, and what new information may we collect from them? The key is to find someone willing to continue to participate in medical experiments — and to properly calibrate each result to match up with Glenn.

Excerpted from Why Am I Taller?: What Happens to an Astronaut’s Body in Space by Dr. Dave Williams and Elizabeth Howell © 2022 Dr. Dave Williams and Elizabeth Howell. All rights reserved. Published by ECW Press Ltd. www.ecwpress.com.