Do you know your resting heart rate, the number of times your
heart beats in a minute when you are being still? More to the
point, do you know that this might be important information to
have? Research now shows that having a high resting heart rate can
predict risk for a heart attack in middle-aged women -- and this
risk is already well-established for men.
Since heart disease remains the nation’s number-one killer of
both men and women, it makes sense to be attuned to all of the
individual risk factors for cardiovascular health and to learn what
we can do about them. To find out more about this lesser known
risk, I called Judith Hsia, MD, the lead author of the research
report, which appeared in the BMJ. "A high resting
heart rate isn’t an emergency," said Dr. Hsia, a former professor
of medicine at The George Washington University School of Medicine
and Health Sciences and currently a senior director for clinical
research with the drug company AstraZeneca. But, she said, if it is
consistently high, it could be a sign that your heart health needs
some attention -- specifically in the form of physical
conditioning.
WHAT THE STUDY FOUND
The study examined data on 129,135 postmenopausal women taking
part in the Women’s Health Initiative study. The women’s radial
(wrist) pulse rates were measured at the beginning of the
eight-year study and again either annually or at one and three
years after the baseline reading. Results showed that women with
heart rates that averaged 76 beats per minute or higher were much
more likely to have heart attacks than women with resting pulse
rates averaging 62 beats a minute or lower. The researchers concede
that the more well-known risk factors, such as hypertension,
diabetes and smoking, are better at predicting a coronary event,
but they say that their study demonstrates that measuring the
resting pulse might be "clinically meaningful."
THE HEART BEATS QUICKLY
Why do some people have a high resting heart rate? One
possibility, said Dr. Hsia, involves the balance between the
sympathetic nervous system, responsible for raising blood pressure
and heart rate... and the vagal component (involving the vagus
nerve, which brings information to and from important organs and
the brain) of the parasympathetic system, which lowers them. These
are both part of the autonomic nervous system, which regulates
involuntary body functions. Dr. Hsia speculates that people with
high resting heart rates may have a sympathetic nervous system that
predominates the parasympathetic system. She explained that a high
heart rate reflects a high "sympathetic tone," which means that the
body is chronically "pumped up," and may be an indicator of
cardiovascular risk. "It’s not the high heart rate that predisposes
women to heart attacks, but rather the high sympathetic tone," Dr.
Hsia said.
STEPS TO TAKE
You can measure your resting heart rate by taking your pulse
at your wrist, counting beats for 15 seconds, and multiplying that
number by four -- but sit quietly for five minutes or so before
sampling to ensure that your body is truly relaxed and that your
mental and physical state are calm. Anything between 60 and 100
beats per minute (bpm) is within the range of what is considered to
be "normal." And individuals’ normal heart rates do differ
depending on their fitness, medications and other health
conditions. Dr. Hsai said that you needn’t be immediately concerned
if your heart rate is higher than 100 bpm, as long as your rate and
rhythm are normal for you and you aren’t feeling dizzy or
lightheaded.
That being said, there’s no doubt that a slow heart rate can
reflect good conditioning, said Dr. Hsia, who recommends a regular
exercise routine for everyone to help the heart and other muscles
function more efficiently. Besides the possibility that it might
lower your heart rate, physical activity is a good way to improve
cardiovascular health and has favorable effects on weight, blood
pressure, blood sugar and cholesterol, as well as on future heart
attack risk. It’s no surprise that people who work out regularly
tend to have resting heart rates about 10 beats a minute slower
than sedentary people and that many athletes have resting rates of
15 to 20 beats a minute lower than average.
"The average adult needs approximately five liters of blood
pumped each minute. If your heart can pump more blood with each
beat, it can pump more slowly," explained Dr. Hsia. "If you’re not
in good physical condition, your heart has to pump more often to
provide your tissues with the blood that they need."
To strengthen your heart and promote overall conditioning,
follow the standard recommendation for 30 minutes of brisk walking
most days of the week. If you haven’t exercised in a while, start
out slowly.
And if you have a high heart rate, mention it to your doctor,
Dr. Hsia advised -- he/she can help put it in perspective compared
with your overall health.