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.
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.”
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.
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.
