People often look to their resting heart rate as a marker of their fitness: While a normal resting heart rate is between 60 to 100 beats per minute, endurance athletes can have one that is quite a bit lower.
But can your resting heart rate hint at something more serious—like your life expectancy?
That’s what researchers from Harvard Medical School are suggesting, after publishing research linking earlier death to an increase in resting heart rate.
In the 28-year study, researchers measured the heart rates of over 15,000 people at subsequent doctor appointments. They discovered that for every five beats per minute increase from one visit to the other—an average of three years between them—people’s risk of death by any cause increased by 12 percent, heart failure by 13 percent, heart attack by 9 percent, stroke by 6 percent, cancer by 8 percent, and death by heart disease by 13 percent. A decrease in resting heart rate, on the other hand, was linked to lower risk
"Heart rate is actually a very good barometer of overall fitness and cardiovascular health. As we become less fit, our heart rates tend to go up, both at rest and with exertion," says study author Scott D. Solomon, M.D., professor of medicine at Harvard Medical School.
So how exactly does an increase in resting heart rate increase your risk of heart attack, or even cancer?
First, it’s likely that heart rate is simply a marker of declining physical fitness and reduced cardiovascular health, Dr. Solomon says.
“In addition, elevated heart rate itself may indeed cause the heart to 'require' more oxygen, and can lead to ischemia—a lack of oxygen—and contribute to heart attacks," says Dr. Solomon
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When it comes to cancer, though, the link to resting heart rate is a little more tricky to explain.
But the study found that changes in resting heart rate increased the activation of sympathetic nervous system, which is responsible for your body's fight-or-fight hormonal response. That’s been directly related to the development of certain diseases, including cancer.
It’s also possible that people with cancer simply have increased metabolic needs, which might elevate their heart rate, says Dr. Solomon. That—on top of their cancer diagnosis—puts them at a higher risk of earlier death.
What Your Resting Heart Rate Means For You
"The data suggests that heart rate going up five points (on average) does increase risk, even if that is within the 'normal' range," says Dr. Solomon. That means you should pay attention to any sustained increase from your baseline, even if your resting heart rate is still within that normal 60 to 100 beats per minute range.
So it's important to have the data on your heart rate to determine how your overall health is, and to recognise that heart rate changes throughout the day and based on activity.
As for measuring your resting heart rate? Well, you could take your pulse right now, but the most accurate way to measure your resting heart rate is to do it first thing in the morning before you get out of bed, according to Harvard Health. Or at least wait one to two hours after exercising or consuming caffeine, both of which can up your heart rate.
"A resting heart rate is when we are lying or sitting sedentary, not exerting ourselves,” says Dr. Solomon. “There is no question that if we walk up a flight of stairs, run to catch a bus etc., our heart rate will increase—and this is normal," says Dr. Solomon.
Once you choose the right time, here’s how to take your resting heart rate: Simply place your index and third fingers on your neck on the side of your windpipe. If you want to check it at your wrist, place two fingers between the bone and the tendon, looking for your radial artery—which is located on the thumb side of your wrist.
Once you find your pulse, count the number of beats in 15 seconds, then multiply that number by 4 to calculate your beats a minute.
And surprisingly, your fitness tracker does a pretty good job too. A 2017 Stanford study found that six out of seven fitness trackers they tested were 95 percent accurate in measuring heart rate.
What is 'normal' for an individual person may vary, but if your resting heart rate increased on average over time, that would be a red flag, says Dr. Solomon. Other things to be aware of include changes in your heart rate, like if it consistently dips way below your normal resting heart rate, or frequent episodes of unexplained fast beating.
And if you exercise regularly and notice your routine is requiring more effort, you feel breathless or more tired during your workout, you should see your doctor.
Other red flags include changes in your heart rate like it consistently dipping way below your normal resting heart rate, or frequent episodes of unexplained fast beating. And if you exercise regularly and notice your routine is requiring more effort, or you feel breathless or more tired during your workout, you should see your doctor, says Dr. Solomon.
This article originally appeared on Men's Health