In recent years, physicians and scientists have come to recognize the importance of the body's internal clock to the vital rhythmic functions such as heart rate, blood pressure and hormone production. Focusing on a sliver of the brain that regulates these functions, the field of chronobiology - the study of the effects of time on life processes - has grown, albeit slowly, into a significant area of medical research.

As the scientific evidence mounts, there is a growing realization amongst these healthcare professionals that patients with uncured diseases can benefit from a regularized living regimen and maintaining a medication program tied to their natural internal clock.

Chronobiologists have seriously challenged the medical community to recognize the importance of body time. Once considered an emerging field, chronotherapy - diagnosis and treatment based on the body's biological rhythms - is now being used to treat a range of ailments, from sleep disorders to depression, and even, in some cases, cancer.

"The internal clock has a whole set of implications for human health," said Dr. Gene Block, director of the National Science Foundation Center for Biological Timing in Charlottesville, Va. “It is important for more physicians and patients to become aware of how important timing is. Happily, that is happening."

Recent research has shown that the intensity of many diseases varies throughout the day, further suggesting that the timing of medication is important. Therefore, it can be expected that a visit to a doctor’s office will also include discussion of the body’s rhythm.

Hypertension - high blood pressure - is thought to affect more than one-third of the population; its diagnosis is often based on one or two readings a day. Chronobiologists argue that because blood pressure varies so much throughout the day, medication should not be administered unless the patient has a 72-hour profile of continuous elevation.

Drug companies are awakening to this need. In 2003, the Food and Drug Administration approved Cardizem LA and InnoPran XL, both time-release medications for hypertension designed to reduce blood pressure in the early morning, when patients are at the greatest risk of cardiac arrest.

Scientists have come to believe that the body tells time through a master clock - the suprachiasmatic nucleus. This is a small cluster of neurons located in the hypothalamus, a gland in the brain. The master clock takes its cues from optic nerves in the retina that respond to levels of light. Using these cues, the clock regulates the body's circadian rhythms, or 24-hour cycle.

Chronobiologists believe that unlike our ancestors, who rose with the sun and slept when night fell, most of us are not in tune with our body's rhythms.

"In our urban existence, with all the electric light and enticing activities at every hour of the day, it's easy for us to lose the sense of ourselves as creatures designed to function in keeping with the rhythms of the planet," said Lynne Lamberg, co-author of "The Body Clock Guide to Better Health." "We may bend the rules of our body clock, but Mother Nature is tough and we will pay the price.”

For persons with diabetes and other uncured diseases, identifying and working with their individual body clocks may heighten the impact of drugs and other treatments on their overall wellbeing.

The cutting edge of chronotherapy is cancer research. Both healthy and cancerous cells show daily cycles of increased reproduction, and some chemotherapy drugs are now being designed to work with these cycles.

In 2001, Dr. Francis Levi, a French physician, published the results of a study he conducted using chronotherapy to treat more than 1,500 patients with gastrointestinal cancer.

He concluded that the patients were much more tolerant of the chemotherapy drugs when they were administered chronotherapeutically, and that survival rates were higher.

At the Block Center for Integrative Cancer Care in Illinois, doctors are using a pump invented by Levi that times the infusion of chemotherapy medication to a patient's body clock.

In a related study, doctors at the Institute of Oncology in Milan, Italy, timed the surgical treatment of more than 1,200 premenopausal women with breast cancer.

Of those patients who had surgery in the week after ovulation, 76 percent were tumor-free after five years, compared with 63 percent of those patients who had surgery earlier in their menstrual cycle.

The results have led some experts to conclude that breast cancer surgery is most effective in the second half of a women's cycle, when progesterone - which may inhibit the production of enzymes that help cancer spread - rises, and estrogen falls.