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Jet Lag and Some Chemotherapy Side Effects May Share Treatments

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WebMD Health News

June 9, 2000 (Atlanta) -- Breast cancer victims and airline passengers may have something in common. The phenomena that cause the rundown feeling common to air travelers, who jet across time zones, may also trigger the fatigue -- and depression -- most chemotherapy patients feel.

Researchers from the University of Rochester Cancer Center in New York believe both may be caused by a disruption of the internal body clock known as circadian rhythm. The researchers presented their findings at the Department of Defense Breast Cancer Research Program Meeting here this week.

Circadian rhythm is described as the regular changes in mental and physical characteristics that occur in the course of a day. Circadian is actually Latin for "around a day." Most circadian rhythms are controlled by the body's biological "clock." It's thought that chemotherapy may disrupt this natural body rhythm.

Lead researcher Gary Morrow, MS, PhD, says that in a recent study of more than 1,000 women receiving chemotherapy for breast cancer, 80% experienced more than a normal amount of fatigue, and some 30% reported suffering from depression. "It's a definite problem that challenges the quality of their life," Morrow, a clinical psychologist, tells WebMD. "It challenges their ability to fulfill their various roles as friends, neighbors, lovers, and parents."

In their study, the researchers looked at the circadian rhythms of 78 patients one week after they received their second or later chemotherapy treatment for breast cancer. Depression and fatigue were evaluated. Each patients' circadian measurement was taken over a three-day period using a device that measures levels of sleep and activity based on the participants' amount of motion.

The researchers found that higher circadian scores -- meaning a more consistent day-to-day pattern of rest and activity -- related to less fatigue and lower depression levels. Also, patients who showed the greatest circadian disruption -- the most irregular patterns of sleep and activity -- reported the most fatigue and depression.

Morrow says the research is preliminary. "It may allow us to try some things that have been useful for jet lag and other circadian disturbances." For example, he hopes such things as light therapy and the supplement melatonin will be studied in the future.

To reduce the effects of jet lag, light therapy is used by some doctors to try to manipulate the biological clock. They expose people to special lights, many times brighter than ordinary household light, for several hours near the time the subjects want to wake up. This helps them reset their biological clocks and adjust to a new time zone.

As for melatonin, Medical College of Wisconsin researchers warn that since the high doses of melatonin found in most over-the-counter supplements can build up in the body, long-term use of this substance may create new problems. Because the potential side effects of melatonin supplements are still largely unknown, most experts discourage melatonin use by the general public.

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