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Medical Author:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Medical Editor:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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In this Article

• What are biologic rhythms?
• How does the "body clock" affects symptoms of illness?
• What are examples of specific diseases affected by biorhythms?
• Angina
• Heart attack
• High blood pressure (hypertension)
• Hay fever (allergic rhinitis)
• Asthma
• Can the "body clock"  affect diagnostic testing?
• Can drug therapy be matched to the "body clock?"
• Chronobiology: marking time, making progress
• Biorhythms Index

The time of day also can affect the way our bodies respond to medical therapy, especially drug therapy. Investigators working in a special area of chronobiology, called chronotherapeutics or chronotherapy, are studying these effects. Their goal is to come up with new medications, or improve existing ones, that make the most of what we know about how the body clock works.

Already there is evidence that taking medication "by the clock" helps the drugs work better and reduces their side effects. Currently, some doctors are prescribing nighttime administration of medication for patients with ulcer disease or asthma (which worsen at night), rheumatoid arthritis (which worsens in the early morning hours), and high cholesterol levels (most of the body's cholesterol production occurs at night). For patients with osteoarthritis, which worsens in the afternoon and evening, some doctors are prescribing midday medication.

Drugs that may be given "by the clock" include corticosteroids, nonsteroidal antiinflammatory drugs (NSAIDs), antihistamines, theophyllines, and anticancer drugs.

These lists are growing as chronobiology, chronotherapy, and the diagnostic and treatment methods derived from them are slowly accepted by the medical community. However, the broad acceptance of chronobiology in medicine is expected to take (excuse the expression) time.

Although chronobiology is not new to medical science, it's still in the process of being accepted by the medical community. That's because most doctors are not taught about chronobiology - in fact, they are taught something that seems to contradict it!

What are doctors taught?

Homeostasis - the concept that body functions are in a constant "steady state" throughout the day and night, and that the goal of treatment is restoring or maintaining this "steady state." Even the treatment itself may have this goal, for example, a prescribed drug is given in a way ("every 4 hours") that theoretically will ensure a steady level of it in the patient's bloodstream. Obviously, this view contrasts sharply with diagnosing and treating illness chronobiologically - "by the clock."

Fortunately, although chronobiology is not yet taught in medical schools, doctors are increasingly taking biologic rhythms into account in diagnosing and treating illness. They are recognizing that whereas homeostatic mechanisms keep the body functioning continuously on a moment-to-moment basis (for example, by maintaining breathing and heartbeat), biologic rhythms program the body "in advance" for coping with its predictably changing needs, such as varying energy requirements, during specific time cycles.

The time is coming, medical experts say, when chronobiology, and particularly the body clock, will play a vital role in many areas of medical practice. In some of those areas, as we've seen, that time is now.

If you are taking medication for a medical condition, consider keeping a record of the timing and intensity of your symptoms for a few days and showing it to your doctor; he or she may want to adjust your therapy to align more with your body clock. Who knows, maybe now is your time to get more into the rhythm of life!

References:

The right time? Chronopharmacology - a new science. Nursing RSA Verpleging. 1992;7:23-27. Pharmacology.

Smolensky MH, D'Alonzo GE. Medical chronobiology: concepts and applications. Am Rev Respir Dis.1993;147:S2-S 19.

Time of day medicine dose is taken may boost its efficacy, cut toxicity. JAMA. 1996;275:1 143-1 144. Medical News & Perspectives.

American Heart Association; "Know the Facts, Get the Stats 2007."

Centers for Disease Control, National Center for Health Statistics; "Allergies/Hay Fever."

Centers for Disease Control, National Center for Health Statistics; "Asthma."