MPR: Working Nights

Working Nights
Part 3

SOUND up: sleep lab
SOUND: (woman) Richard? We're going to do subcals now. With your head still, please open your eyes and look straight ahead. With your head still, please close your eyes.

Researchers at Harvard medical school are studying the body's circadian rhythms by sequestering human volunteers in windowless isolation rooms at Brigham and Women's Hospital in Boston. The scientists are studying ways to artificially shift a person's circadian rhythms.

SOUND: (man) He closed his eyes here, because the EEG's are more evenly spaced.

It's just after noon, but for the 26-year-old fellow in room four it's bedtime. Lab technicians watch him on a TV screen while monitoring his brain and body functions by computer. The subject is taking melatonin, the hormone that some people use as an over-the-counter sleep aid or to cure jet lag. While melatonin seems to work for some people, many doctors warn it's not gotten enough study to be considered safe for general use. At Harvard, researcher Charles Czeisler is seeing whether melatonin can be used to reset the circadian pacemaker.

Charles Czeisler: The subjects in the melatonin study are actually on a 20 hour day rather than a 24 hour day. So that means every day for a month they're going to sleep four hours earlier than they did the day before.
Smith: You mean that poor guy has been in there for a month? I shouldn't say that. I'll back up. You meant that guy has been in there for a month?
Czesiler: (laughs) Well, by the end of his study he will have been here a month. So each day he's doing the equivalent of flying eastward across four times zones. And in this way we are able to evaluate sleep, taken at all different times of day, even though there's the same amount of wakefulness before hand.

In the 19th century, scientists recognized that plants and simple organisms set their daily rhythms by the sun. But humans, believing themselves too advanced for that that, thought sleepiness a mere urge to be conquered with willpower. In the last 20 years, Charles Czeisler and his Harvard colleagues proved that human circadian rhythms are also calibrated by sunlight. When light hits the eye, it sends a signal to the pacemaker, setting the internal clock. Czeisler and others believe that modern-day life under electric lights actually confounds the timing of our internal clocks, especially in the evening.

Czeisler: That allows us to stay up at a time when we normally would not physiologically have the desire to stay up.
Smith: We'd want to be in bed by?
Czeisler: Ten o'clock or even earlier. So we have propelled our bedtimes to a later and later hour. And then we're still trying to get up six, seven, eight o'clock in the morning in order to get to work.

Czeisler adds that most of us are so accustomed to this sleep-deprived schedule we can't remember what it actually feels like to be well-rested and alert. The result, he says, is chronically lowered mental performance, reaction time and memory.

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