Scientists have long known that the body is governed by biorhythms, such as the circadian (24-hour) rhythm or the monthly menstrual cycle. Now a growing body of research shows that treating patients according to their biological clocks can have a huge health pay-off.
The field is called chronotherapy—in essence, “timing medications or therapies according to the body’s biological rhythms to optimize the benefits of medications and minimize or avoid side effects,” says Michael H. Smolensky, M.D., an adjunct professor in the biomedical engineering department at the University of Texas at Austin. These examples show where the field is headed in treating common health problems:
*High Blood Pressure: A new study from the University of Vigo in Spain followed patients with high blood pressure for five years, comparing those who took their blood pressure lowering medications at night to those who took them in the morning, as is often prescribed. The result: Patients who took their medicine at night not only had better control of their blood pressure, but also experienced fewer heart attacks and strokes, says Smolensky, a study co-author. The drugs prevent the release of chemicals synthesized during sleep that raise blood pressure to abnormal levels.
*High Cholesterol: Research from Long Island University in Brooklyn showed that taking simvastatin, the “statin” known as Zocor, at bedtime was better at lowering “bad” LDL cholesterol than when taking the medication at in the morning, and the FDA now recommends that it and the statins, lovastatin and fluvastatin, be taken at night. The drugs block a key cholesterol-making enzyme in the liver that is most active at night. (Other statins—atorvastatin, rosuvastatin and pravastatin—stay in the body much longer so can be taken in the morning.)
*Asthma: Lung function reaches a low point in the early morning, aggravating asthma symptoms of patients with the condition. Doses of some asthma medications—particularly the bronchodilator theophylline—may thus be timed to peak at that time, Smolensky says.
*Arthritis: Arthritis medications including nonsteroidal anti-inflammatory drugs (ibuprofen, naproxen sodium) are typically scheduled to attack pain and inflammation when they strikes hardest—in the evening for patients with osteoarthritis and in the morning for those with rheumatoid arthritis.
*Cancer: The findings for cancer treatment are intriguing but still evolving. For instance, while some studies show that scheduling breast cancer surgery for premenopausal women during the first half of women’s cycle boosts survival rates, other data suggests the latter half is optimal. According to Smolensky, there are hints that chemotherapy may be more effective when given at particular times of the day.
The science of chronobiology may eventually yield clues for cancer prevention, too. A study in mice at the University of North Carolina at Chapel Hill showed that the ability of the brain to repair DNA damage was at a minimum in the early morning and reached a maximum in the evening due to the effects of an enzyme called XPA, which is linked to skin cancer. If the findings hold up in human studies, it could suggest specific times of the day to avoid cancer-causing sunrays.
CONNECT THE DOTS
For a list of helpful resources on chronotherapy, go to the website of the American Association of Medical Chronobiology and Chronotherapeutics.
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