During Follini's subterranean stay, her sense of time had elongated. Her "day" extended to 25 hours, then to 48 hours. She tended to sleep for 22 to 24 hours, then burst into activity for up to 30 hours. She ate less frequently and lost 17 lbs. Her menstrual period stopped. In short, her internal biological clocks had gone out of whack.
The New Mexico experiment called attention to an emerging field in science called chronobiology, the study of the body's innate, rhythmic patterns. Today researchers realize that many human characteristics, from basic physiological functions such as blood pressure and body temperature to mental sharpness and moods, follow such patterns. Some cycles are as brief as seconds; the heart's permeability to certain chemical ions appears to shift back and forth in less than a minute. Others are measured in months; some people regularly fall into deep depressions in winter and cheer up in summer.
The best-known rhythms are circadian, from the Latin, meaning "about a day." The sleep-wake cycle is the most obvious, but the body's production of hormones also fluctuates significantly over 24 hours. Says Charles Ehret, president of General Chronobionics, a research and consulting company in Hinsdale, Ill.: "Chemically, you are a very different person at noon than you are at night."
Controlling the daily cycles is a cluster of 10,000 nerve cells -- altogether about the size of the head of a pin -- that are located in the hypothalamus, a segment of the brain. Some biological timepieces appear to take their cue from temperature or barometric pressure, but many are synchronized with the cycle of light and darkness caused by the rising and setting of the sun. Experiments conducted in caves, like the one in New Mexico, and others in special laboratories purposely remove all such cues. In Follini's module the temperature was a constant 69 degreesF, and the only illumination was artificial. The aim of such experiments is to get the body to "free-run" and see what sort of patterns it establishes on its own.
The conditions of Follini's underground life were extreme, but people's biological clocks can also be disrupted by the demands of everyday life. Jetting across time zones, working twelve-hour days or irregular shifts and even sleeping late can disturb biological rhythms and impair efficiency and judgment. Government officials and business leaders are routinely advised to recover from jet lag before starting negotiations.
Investigators analyzing the blowup of the Challenger shuttle and the disasters at Three Mile Island and Chernobyl have found that in each case, critical errors were made by people struggling with unusual work schedules and lack of sleep. The two nuclear plant accidents happened in the wee hours of the morning. Similarly, most truck wrecks related to fatigue occur between 2 a.m. and 4 a.m. "Shift workers classically have to perform when their brains are trying to put them to sleep," observes Dr. Charles Czeisler of Boston's Brigham and Women's Hospital. "They are fighting the internal clock." Many workers run on automatic pilot at that time; they execute routine tasks but are unable to process new information, like flashing red lights that signal danger.
More sensible work schedules could reduce such hazards. In a recent eleven- month experiment in Philadelphia, police were put on a revised rotation that meshed better with their innate clocks. The number of days worked consecutively was cut, and the officers were not moved from one shift to another as frequently. Police on the new schedule had 40% fewer patrol-car accidents than before, and their use of sleeping pills and alcohol dropped by half.
Chronobiology also has implications for medical treatment. Diagnostic tests can be misinterpreted if doctors are not aware of biological rhythms. For instance, patients may react more strongly to allergy tests that are given in the evening than to the same tests done in the morning. Last week Dr. William Hrushesky of Albany Medical College reported that women who undergo mastectomies during their menstrual period appear to have a higher risk of dying from breast cancer within five years than women who are operated on in the middle of their monthly cycle. Hrushesky speculates that hormones produced during menstruation somehow have a negative effect on the body's immune system.
In the most promising medical application, doctors are beginning to time medication to match biological cycles. Some experts believe the effectiveness + of cancer treatments can be boosted -- and the harmful complications of the often toxic drugs lessened -- by taking advantage of daily rhythms in the immune system and cell division. Painful bouts of rheumatoid arthritis occur most frequently in the morning, when natural anti-inflammatory agents are least active; aspirin affords the best relief when taken the night before. On the other hand, the time to take medication for osteoid arthritis is midday; joints become inflamed with movement, and pain occurs later in the day.
Scientists are also exploring ways of resetting the body's clocks. Among the possible methods: using exercise, changing diet, or varying the amount of light or sleep. Even chemical intervention is being considered. Says neurobiologist Fred Turek of Northwestern University: "One of our goals is to find safe drugs that can speed up your clock or slow it down." Such techniques offer the possibility that one day, humans will be not just captives but masters of biological time.
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