Chronobiology: The Rhythm Method for Overall Health
For better health, groove to the beat of your
By Cynthia BeMent
December 18, 2000
locks. We're always
answering to them -- they tell us when to wake, when to eat, when
to go to work, and when to fall exhausted into bed at night. These
oft-cursed timekeepers set the rhythms to which our bodies and
minds dance daily. Or do they?
A new field of science called chronobiology suggests that it's
really a clock within our body that produces the rhythms that
rule our lives and our health. Chronobiologists and doctors who
practice chronomedicine are discovering that the key to better
managing illnesses ranging from the common cold to cancer lies
within this timepiece inside the brain.
Big concept, little awareness
Chronobiology is the science of "body time" -- the way our internal
clock, a tiny bundle of cells in the hypothalamus, controls the
hundreds of regular bodily functions that sustain life. Called
the suprachiasmatic nucleus (SCN), the internal clock works with
information from light receptors in your eyes' retina to render
body time each day.
The SCN conducts the orchestra of biological life, controlling
daily fluctuations in functions such as heart rate, blood pressure,
body temperature,and hormone secretion. Its rhythms do things
like regulate your sleep/wake patterns, make you a morning person
or a night owl, control concentration, and give you your best
physical coordination in late afternoon. These rhythms also produce
longer body cycles, such as the female menstrual cycle and reproduction.
If chronobiology is news to you, chances are it's news to your
doctor too. A 1996 Gallup survey conducted for the American Medical
Association found that over half of the 320 physicians asked were
unfamiliar with chronobiology, and that only one in three had
been taught chronobiology in medical school.
Why aren't most doctors tuned in to body time? "The prevailing
concept [taught in medical schools] is one of homeostasis, meaning
that the body is held constant," says Michael Smolensky, Ph.D.,
co-author of The Body Clock Guide to Better Health (Henry
Holt, 2000). "At the turn of the twentieth century, when most
modern concepts of medicine were established, doctors didn't have
the technology to run tests more than once a day," says Smolensky,
who directs the Chronobiology Center at Herman Hospital, in Houston,
Texas. "Today with improved technology, we've been able to see
that the body is anything but constant."
The timing of disease
Body rhythms have been shown to affect not only daily, weekly,
monthly, and yearly functions, but also the prevalence of disease
symptoms, medical test results, and even the way the body responds
to drug therapies. "The occurrence of disease is not a random
process," says Smolensky. "There is a biological time structure
Symptoms You Can Set Your Clock By
In The Body Clock Guide To Better Health, co-authors
Michael Smolensky and Lynne Lamberg list more than
30 conditions and diseases affected by body rhythms.
The worst times of day for certain symptoms are as
Menopausal hot flashes
Chronobiologists have found that for conditions ranging from
depression to heart disease, the severity of symptoms varies throughout
the day (see sidebar). Heart attacks, for example, are "40-50
percent more common during the first 6 hours of daily activity
than during sleep," says Smolensky, adding that "even chronic
conditions such as arthritis, asthma, hay fever, and headaches
show marked variations in their symptom severity [throughout the
By keeping track of these variations, Smolensky says, we can
schedule doctors' appointments and daily activities, like exercise,
at optimum times.
On the flip side, a lack of awareness about these rhythms can
aggravate symptoms and hinder early diagnosis. Franz Halberg,
M.D., who is known as the father of chronobiology and who in 1959
coined the term circadian rhythms, says blood pressure
readings, which vary throughout the day, provide an example. "[At
a yearly doctor visit] a single blood pressure reading can be
perfectly normal. You can be completely asymptomatic at the time,
but still be at high risk for stroke," says Dr. Halberg.
Setting body rhythms to therapeutic music
One of chronobiology's most significant impacts on medicine is
chronotherapy, the synchronization of drug delivery with body
rhythms. This involves both restructuring the times of day existing
medications are taken and developing a new breed of "body time-savvy"
drugs called chronotherapeutics. "Certain ones have special drug-delivery
technology -- their release is synchronized to the peaks in the
disease symptom cycles to help manage symptoms more effectively,"
One such drug already on the market is verapamil hydrochloride
(Covera-HS), introduced in 1996 for the treatment of high blood
pressure. Taken at bedtime, verapamil hydrochloride releases nothing
for about four hours, then kicks in and begins to release medicine
just before the waking hour, when blood pressure rises most sharply
in its effort to rouse the body from sleep. The amount of medicine
released tapers down as the day goes on.
"Patients should talk with their doctors and pharmacists to make
sure they know the recommended times to take medications during
the 24-hour sleep/wake cycle," notes Smolensky.
Chronotherapy has also proven effective in treating women with
ovarian cancer. Researchers in the United States, Canada, and
Europe are aiming to recruit 884 women with breast cancer by 2002
in order to study how the timing of breast cancer surgery during
a woman's menstrual cycle effects her chances for survival.
Keeping better body time
Chronobiology isn't just a disease thing, though. "Any person
can be in touch with his or her own body rhythms," says Lamberg.
Women can begin by tracking their menstrual cycles, and both
Smolensky and Halberg recommend frequent self-assessment for early
detection of potential problems. "We should get these baseline
measurements before disease sets in," says Smolensky. You should
share your findings with your doctor to create an open dialogue
about body rhythms and disease.
"We should be tracking our moods, our alertness, and even our
children's sleep cycles," says Smolensky. "Body rhythms are part
and parcel of our existence." By staying in tune with the most
important clock of all, we can lead a healthier, more harmonious
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