By Abigail Trafford
Washington Post Staff Writer
Tuesday, October 13, 1998; Page Z6

John Glenn may be a hero on the ground, but the 77-year-old senator will be a guinea pig in orbit when the he blasts off into space on Oct. 29.

The former Mercury astronaut, who spent less than five hours in weightlessness when he became the first American to circle the Earth in 1962, will spend nearly nine days on the shuttle Discovery as the nation's prime-time medical subject. He'll sleep with electrodes in his scalp and a respiration sensor under his nose. He'll swallow a pill with a radio transmitter to monitor his temperature and circadian rhythms. He'll wear a Holter recorder to watch for heart irregularities. At frequent intervals during the flight, he will give blood for various experiments. Even the pilot, known as "backup vampire," is trained to draw Glenn's blood.

What makes the former astronaut such a good guinea pig is his advanced age. "The idea is to evaluate the differences in physiological response of an older individual compared to the database of younger individuals," says John B. Charles, medical scientist at the Johnson Space Center in Houston.

Scientists have long documented that the bodily changes which occur in weightlessness mimic some of the changes associated with aging. In both spaceflight and with age, there are major losses of bone and muscle, depression of the immune system, difficulty sleeping, dizziness and balance problems. Blood volume drops; indeed, taking a trip in zero gravity is the equivalent of making a couple of blood donations.

With space travelers, these changes are reversible. With the elderly, they can lead to the general frailty associated with the very old and such debilitating conditions as osteoporosis.

No one is expecting the mystery of aging to be solved with a few experiments on one very fit, lifelong jet jockey who power-walks two miles a day on Earth and has passed all his preflight physical tests. But scientists hope to find clues to some of the mechanisms of aging by putting a person well on the way to octogenarian status into an environment that is known to bring on changes similar to aging. In effect, Glenn is subjecting himself to the double stress of natural old age and the artificially induced "aging" of spaceflight.

Scientists speculate that the impact of weightlessness may be greater on an older person and accelerate these changes. Or perhaps it will be just the opposite. Age may have a protective effect against these changes.

"That's the Glenn hypothesis--the 'if space flight is like aging and I am already aged, then I am partially adapted to space flight,' " explains Charles. Whatever the results, which won't be completely analyzed for a year, "this is win-win," he says.

Getting a Good Night's Sleep
One major problem astronauts share with the elderly is getting a good night's sleep. In fact, there is no real nighttime on shuttle flights. "The sun is rising and setting every 90 minutes, there's no place to lie down and sleep, you're in with other people in a room a tenth the size of a motel room," says physician Charles A. Czeisler of Brigham & Women's Hospital in Boston who is in charge of the sleep experiment on Discovery.

Most astronauts average about six hours of sleep out of 24, and some only get a few hours. On flights with night duty, 50 percent of the crew take sleeping pills.

Older people also have trouble sleeping. They too sleep fewer hours and their sleep is more disrupted. In many cases, daytime symptoms of lethargy and confusion can be traced to a lack of sleep.

To understand these sleep disturbances, Glenn and physician Chiaki Mukai, 46, from the Japanese Space Agency, will be closely monitored while they sleep. For four nights, they will wear special caps with electrodes placed on their scalps to measure brain wave activity. Electrodes will also be placed on their faces to measure muscle tension, a device on their wrists to measure movement, a monitor to measure breathing.

In addition Mukai will test the effectiveness of the hormone melatonin as a sleep aid.

Glenn and Mukai have already been through this drill on the ground to give researchers a baseline for their sleep patterns. They will also be studied after the flight and their data compared to the results of tests on four astronauts on a previous flight.

"We don't know the underlying mechanisms of sleep disruptions," says Czeisler. "If we could learn what triggers these changes in older people by learning how they are triggered in space," that might help direct research into developing effective treatment. "It may provide clues to which way to go," he says.

Losing Muscle and Bone
Shrinking is another feature space travelers and the elderly have in common. On long space flights, crew members lose on average 1 percent of their bone density a month. On the ground, a person who loses 30 percent of bone mass over a lifetime is diagnosed with osteoporosis. Bone loss and muscle wasting are much more rapid in space than among the elderly. Significant loss of muscle can occur after five days in weightlessness. In-flight exercise programs have proved helpful but "did not fully prevent deterioration," concludes the National Research Council. Nor, as gerontologists know, can exercise alone fully counteract the devastation of osteoporosis on the ground.

To help unravel the tangled processes of bone and muscle loss, Glenn will regularly give blood and urine so that researchers can measure exactly how much muscle mass he loses during the flight--and see if there are differences between Glenn's experience and that of his younger crew mate, Pedro Duque from the European Space Agency.

First Glenn and Duque will have to record exactly what they eat by scanning bar codes on pre-weighed portions of food. Then they will swallow pills containing the amino acid alanine, a building block of the protein that makes up muscle. By tracking the levels of alanine in blood and urine samples, researchers can measure how much protein is being built up and how much is being broken down--a process called protein turnover--and calculate the degree of muscle loss. In addition, another amino acid, histidine, a component of muscle, will be directly injected into the bloodstream to give scientists another measure of the breakdown of protein during the flight.

With these samples, Arny A. Ferrando of the University of Texas Medical Branch at Galveston will be able to determine the exact rate of muscle loss over time. Ferrando suspects that the body's hormones are also involved in this wasting process. He plans to measure cortisol and insulin in the blood samples to see if these hormones rise when muscle loss increases. That would make sense, according to Ferrando, because during times of stress, these hormones are known to increase and muscle is used as a source of energy. Since spaceflight is stressful, notes Ferrando, that might help explain the dramatic rate of muscle loss among astronauts.

Discovery crew members will also undergo magnetic resonance imaging (MRI) scans to assess damage to muscle and the spine and document changes in the bone marrow. This ongoing experiment has already evaluated 16 veterans from the Russian space station Mir and four from previous shuttle flights, including Discovery commander Curt Brown, who will be tested again.

Once on the ground, space travelers generally recover their preflight strength. "We might see a delayed recovery in an older individual," says Adrian LeBlanc at Baylor College of Medicine in Houston, who is conducting the MRI study.

"As you age, you lose muscle mass," putting less of a load on the bones, "so you lose bone. In space, the loading on the bones and muscle goes to zero," he says.

"What spaceflight can do is isolate this factor of reduced loading. What role does it play compared to hormonal changes and other changes of aging? It's clear these mechanical loading forces are critical," continues LeBlanc. "We have to understand what triggers bone loss. Then we can have a much more effective way of targeting the system."

Space travelers generally minimize the medical stresses of Earth orbit. "Pretty transient stuff," says Joe Allen, a veteran of two shuttle missions who is now chairman of Ceridian Corporation, an aerospace company. And he notes that the ones who feel the effects the most and show the most degradation "are the people who were in the best shape to begin with."

For Glenn, the upgrade from Mercury to shuttle status will be like going first-class into orbit. Not only are the accommodations grander, but the ride is gentler. Instead of up to 7.9 Gs pressing on him during the ascent into Earth orbit, he'll pull only 3 Gs, or three times the Earth's force of gravity.

And while he is the oldest American to go in space, he's not the only person of a certain age to take a trip in zero G. Deke Slayton, also one of the original seven astronauts, didn't get a flight until he commanded the Apollo-Soyuz rendezvous in 1975 at age 51. When asked how it felt to be an old guy in his fifties going up in space, he reportedly quipped, "Hell, my grandmother could have made this flight."

Since then, astronauts Vance Brand and Story Musgrave were both in their sixties when they made shuttle flights. In another kind of milestone, astronaut Shannon Lucid was 53 when she completed a six-month stint on Mir in 1996, setting the record for time in weightlessness among U.S. space travelers and becoming a symbol of the Right Stuff for older women.

Glenn is just pushing the edge of the aging envelope out a little farther. As gerontologist Robert N. Butler says: "No one is going to look at Granddad the same way when John Glenn gets back. This could be a nice strike against ageism."