FOR two weeks before their scheduled launching last May, four crew members of the space shuttle Columbia used brute force to readjust their biological clocks so they could work the night shift. They willed themselves to stay up through the night, watching old movies to stave off slumber. By day, they took to their beds, tossing and turning, determined to sleep. They ate dinner at dawn and breakfast at night.
Although they had the right stuff, they felt awful.
"I didn't sleep well," said Ron Parise, a payload specialist. "I didn't eat well. I was exhausted."
So when a fuel leak pushed the mission back until fall, the astronauts decided to try different approach.
Just before the new launching date, Dr. Charles Czeisler, a Harvard expert on sleep disorders, reset the crew members' 24-hour biological clocks using a method that involves exposure to timed doses of bright light. Over three days, he shifted their sleep-wake cycles so that by the 1 A.M. launching they were night animals.
"I guess you could say it was like night and day -- we certainly became disciples," said Robert Parker, who recently retired from the astronaut corps. "When we started our shift we felt like it was morning, even though it was really the middle of the night."
Because of such glowing reports, the crew that is to be launched today aboard the space shuttle Discovery has been similarly prepared.
Light has recently emerged as a powerful modulator of circadian rhythms, those inexorable cycles of drowsiness and wakefulness, hormonal ebbs and flows. Now scientists are prescribing doses of bright light to try to solve a variety of problems: jet lag, the disturbed sleep of the elderly and the complaints of night workers.
Although Dr. Czeisler had successfully used light to reset rhythms in his lab, the Columbia mission was the first real-world trial of the new technology. But once perfected there will probably be others: Dr. Czeisler has already talked with two European airlines about the feasibility of installing bright lights in airplane cabins to help long-haul business travelers adjust to the time zone of their destination.
"Everyone has been very pleased so far," said Dr. Al Holland, chief of the behavior and performance lab at the Johnson Space Center in Houston. "But it's a new technology and we're still learning."
"If you look at the litany of things that have come down the pike for sleep problems, Chuck Czeisler's are at the top," said Dr. R. Curtis Graeber, manager of flight deck research at the Boeing Commerciial Airplane Group in Seattle, who has studied sleep problems in pilots.
But, he said, the light treatments may be more difficult to carry out in other less-controlled circumstances. 'Not Free People'
"Astronauts are not free people," he said. "They are kept in a cage." The astronauts are in quarantine for a week before launching, and light exposure in their quarters can be carefully controlled.
Dr. Czeisler and his colleagues had been accumulating the knowledge needed to successfully reprogram the astronauts' rhythms since 1986, when they first showed that light exposure could disrupt and reset the daily pacemaker in humans. This pacemaker, a brain center called the suprachiasmatic nucleus, is connected to light-sensing cells in the eye and orchestrates a wide variety of 24-hour internal cycles, including alertness, levels of adrenaline and rapid-eye-movement or REM sleep, the deepest stage of sleep.
Previously, scientists had recognized light as the organizing principle of the days of lower mammals, but considered social cues, like eating dinner or the morning coffee, to be more important in man.
The researchers used light about the intensity of that present just after dawn, or 10,000 lux. That is one-tenth as bright as the midday sun, but a hundred times brighter than any indoor light. They discovered that doses of light, lasting five hours, had different effects on the human clock when delivered at different times of day and pieced together a timeline of how light exposure at different times influenced human rhythms.
At some points, the light doses would shift the clock forward, at others they would push it back, and at still others, the doses had little effect. Adjustments were largest when the light was delivered during the humans' habitual night. A light dose early in the night delays the clock to a later hour; a dose late in the night advances it to an earlier time.
More recently, Dr. Cziesler and his colleagues found that they could alter the strength of the cycles as well as their timing. In a study reported in the journal Nature last month, they found that precisely timed doses of very bright light dampened the peaks and troughs of the daily cycles so much that they abolished the grinding native rhythms of hormones, of wakefulness and sleep. Subjectively, one of the subjects noticed that he did not experience the profound tiredness that punctuates a normal day, although he still became a little sleepy from time to time. Cold Turkey Preferred
The resultant calm makes the clock easier to reset. Comparing the rhythms of life to waves on the sea, Dr. Czeisler said: "If the ocean is still, the wake of man's boat will be the dominant wave. But if there are high seas, with seven-foot waves, the wake of the boat won't make much of an impression because it will be overwhelmed by the swells."
Last fall NASA called Dr. Czeisler, head of the Laboratory for Circadian and Sleep Disorders Medicine at Harvard's Brigham and Women's Hospital, to Houston to put these principles to work on the Columbia night crew members. The astronauts had just spent more than a month on a forced inverted schedule.
"Not only were they out of sync with their biological rhythms, but they had essentially been sleep-deprived for weeks," Dr. Czeisler said. "If that was how they were going to prepare for the launch, they would have been better off launching cold turkey."
Although the astronauts had stayed awake at night, the indoor light was not bright enough to reset the internal clock. Also, after a night awake, the crew members would sometimes go jogging outdoors before retiring to bed. The light told their bodies that it was morning, time to wake up. Some of the crew members resorted to sleeping pills.
To accommodate the astronauts, Dr. Czeisler's team outfitted a conference room at Johnson Space Center with enough light bulbs and white light-reflecting paper to serve as an indoor light chamber where the crew could get 10,000 lux. They adjusted the timing of the light treatments, which generally lasted about eight hours, to accommodate the crew's hectic pre-launching schedule, since some activities could not take place in the light room.
"They gave me a schedule." Dr. Czeisler said. "Most of the time I didn't know what they were doing, but all I kept asking is what's the intensity of the light there?" Steak or Cheerios
At the end of the adaptation period, tests showed the astronauts were biologically adapted to their inverted schedule. Urine levels of the hormone melatonin, which the brain releases only during its true sleep phase, were high during the crew's daytime sleep, and low during their waking night. Forced sleep during the day does not result in melatonin release, Dr. Czeisler said.
The crew member's diaries recorded no sleep disturbances after the second night of adaptation. More important, when they went to work at night they felt raring to start the "day."
"At first when we got up at 5 P.M., we couldn't decide whether to have steak and salad, or Cheerios," said Dr. Parise. "After a few days I went with Cheerios. For me it was morning. Looking at salad and Roquefort dressing just seemed disgusting."
After launching, the crew members were able to maintain their inverted schedules merely by sleeping their appointed eight hours in total darkness, since there were no external cues to disrupt their newly set clocks. As the shuttle orbits, light and dark alternate every 90 minutes, but that cycling seems to be too rapid to affect the human pacemaker, Dr. Czeisler said.
Scientists hope that light therapy will yield solutions to more mundane problems as well. For example, circadian rhythms drift to an earlier hour as humans age so that elderly people are often out of tempo with the rest of the world, getting tired early and waking up at 5 or 6 A.M. Their daily body temperature cycles and hormone release rhythms are shifted forward as well. Briefcases With Lights
Bright light exposure at night could push back the clock of an elderly person, bringing him in step with the rest of the world, Dr. Czeisler said. Airline crews, tourists and business travelers might also be helped.
So far, in practice, human-clock reprogramming has required long exposures to bright light each day for several days, making the method useless for airplane flights. But Dr. Graeber said new research suggests that more limited exposures at the right time could have equal effect.
And then there is the technical problem of creating 10,000 lux of light indoors. It might be difficult to wire an airplane cabin for that much electricity and to dissipate the heat that the lights would generate.
Scientists say that entrepreneurs have been too quick to market the concept. "The whole thing has been hyped and exploited prematurely," Dr. Graeber said, noting that companies are already selling "bright lights in a briefcase" as a purported aid to business travelers. He said that legitimate applications should await scientific research on how to administer light therapy and technical improvement in providing high intensity lights in a closed space. "Remember," he said, "jet lag isn't cancer." STANDING TIME ON ITS HEAD Astronauts had their internal clocks adjusted by doses of bright light timed to reset a brain center called the suprachiasmatic nucleus, which governs daily cycles. The doses of light can either advance or delay the internal clock, depending on timing.