While Senator and first-American-to-orbit-Earth John Glenn once again gained national attention last week--this time for his role as a geriatric guinea pig aboard the space shuttle Discovery--Dr. Charles A. Czeisler, professor of medicine at Harvard Medical School (HMS), was busy investigating Glenn's sleep patterns.

The scientific community is hoping that Czeisler, NASA's principal investigator into space-related sleeping disorders, may soon have valuable data that will help both NASA's astronauts and Earth's elderly get a good night's sleep.

"Space travel and aging have similar effects on sleep, and the research data we gather from Senator Glenn's participation might provide insight into age-related changes in sleep as well," said Czeisler at a press conference prior to the shuttle's launch.

As NASA has pointed out, there were 17 million people aged 65 years or older in the U.S. in 1963, just one year after Glenn made his historic flight. Today, there are twice as many.

In addition, the number of Americans 85 or older is expected to skyrocket from 3.3 million today to 18.9 million by the year 2050. Studies have shown that the physiological problems associated with the low gravity of space travel--for instance, cardiovascular de-conditioning, balance problems, depressed immune response and, of course, disturbed sleep--parallel age-related problems.

As part of the experiment, Glenn and Dr. Chiaka Mukai, a payload specialist from Japan, spent four nights wired to sensors that monitored breathing, muscle tension, brain waves, oxygen levels and eye and body movement. After their return Saturday, they slept at Johnson Space Center in Houston, still wired to the sensors. They will continue to give blood and urine samples for the next few weeks. Czeisler was still in Houston yesterday according to his secretary, and could not be reached for comment.

The study is also looking at the use of melatonin, a hormone produced in the brain, to ease sleeping disorders. While Mukai participated in this part of the experiment, Glenn was disqualified for reasons NASA would not disclose. Although melatonin is currently used by millions of Americans looking to improve their sleep, its effectiveness is uncertain. Mukai was given a placebo on some nights and melatonin on others. Besides studying the effects on her sleep, Czeisler will test its effects on Mukai's cognitive performance and short-term memory.

If results are positive, NASA hopes to use this as an alternative to other drugs that can interfere with daytime activities. Currently, more than 50 percent of astronauts use sleeping aids to counteract sleep disruptions caused by confined spaces, intensive work shifts and the 45-minute day-and-night periods.

Researchers think that age-related sleeping problems are caused, at least in part, by improper synchronizing of the human circadian pacemaker, or the "body clock." Currently, however, no one is sure how this happens, although it has been noted that bright light can help both aging people and astronauts "reset" their pacemakers.

By taking careful measurements of the effects of gravity on an astronaut's health, including how he or she sleeps, both NASA and gerontologists hope to see if the mechanisms of space-and age-caused sleep disturbances are the same.

Right now, no one's sure, but the scope of the questions raised include whether these things are inevitable and what can be done to reverse them.

It will be a while, researchers say, before we know for sure. It may even be a while before the data from the flight is released to the general public. NASA is still grappling with privacy issues, including whether they should release John Glenn and other astronauts' medical information.

Glenn, who said that he found this trip easier in some respects than his last, and that he "slept like a log" his last night in space, nevertheless appeared somewhat shakier than the other astronauts as he disembarked from Discovery.

If Glenn is recovering more quickly, it may mean that the biological mechanisms behind aging-and zero-gravity-caused deterioration are indeed the same, said John Charles, of NASA's life-sciences division.

It would suggest that he is already somewhat adapted because these changes have already occurred in his body. But, Charles said, if the other astronauts recover faster, it may indicate that these processes are different, with Glenn having to overcome both gravity-associated problems and the slower healing time often associated with old age.