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Exercise Heart Rate Predicts Death
Sept. 21, 2003 -- How quickly your heart rate bounces back from intense exercise may predict future risk of dying from heart disease, according to a new study of women, half of whom die from America's top killer -- usually when they have few or no outward symptoms.
After studying some 3,000 women for 20 years, researchers say that even seemingly healthy women whose hearts take longer to slow down after exercising to the point of exhaustion are more than three times more likely to later die from heart disease.
This finding, published in this week's issue of The Journal of the American Medical Association, follows another study published three weeks ago that also suggested that heart rate recovery may be an important predictor of future heart disease death.
Men's Failing Hearts
The previous study, in the Journal of the American College of Cardiology, showed that older men whose heart rates did not slow down by at least 12 beats within the first minute after a treadmill exercise stress test were more than twice as likely to die from heart disease in the future. However, most of those 3,000 men either had existing heart disease or were considered likely candidates for it.
But in the new study, researchers found that even when free of heart disease symptoms, women face a higher future death rate when their heartbeat drops fewer than 10 beats per minute from its target heart rate zone, the intense heart-pumping levels achieved in vigorous workouts. This new study involved women as young as age 30, and none had significant heart disease risks when enrolled.
It's especially important because women are more likely than men to die from heart disease without first displaying symptoms or having risk factors.
Target heart rate is 220 minus your age. The researchers subtracted 5 from this number if the person was physically active -- since their heart rates were more likely to be lower to start with.
Treadmill Tests Predict Risk
The findings from both studies suggest that popular treadmill stress tests may be useful in predicting future risk of dying from heart disease. Currently, these tests are primarily used to diagnose heart disease, and not predict it, and are usually given to men suspected of having impaired blood flow or other risks; in women, the tests are deemed less reliable.
"In women, exercise stress tests are used less often because women tend to get more false positives," says lead researcher Samia Mora, MD, MHS, of Johns Hopkins School of Medicine. "And they're rarely done when women don't have outward symptoms of heart disease."
The stress test involves first walking and then running on a treadmill that steadily increases in speed and inclines while the doctor measures heart rate, blood pressure, and the heart's electrical currents. Based on these findings, they can determine if there is adequate blood flow to the heart during increased activity.
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