A man checking his heart rate variability with the help of a smartwatch.

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Heart Rate Variability Is the Health Metric You Should Be Paying More Attention to—Here's Why

Knowing your heart rate variability (HRV) can clue you into your overall health. Here, experts explain what you should know.

By Katherine Hobson Updated May 23, 2024


Thanks to wearable devices, there’s more health data than ever available to us. Some indicators, like heart rate, don’t need much explanation. But others may be new to you. One popular metric: heart rate variability, or HRV. It’s worth keeping your eye on as an indicator of your overall health and as an incentive to keep up good wellness habits. Below, find everything you need to know about HRV and its connection to your health.

What Is Heart Rate Variability (HRV)?

Your heartbeat may feel steady, but even when it’s thumping along at a resting average of 60–100 beats per minute (or higher when you’re exercising or moving around), there’s a tiny variation in the interval between heartbeats. That fluctuation is defined as heart rate variability (HRV). 

“Our heart rate isn’t constant or static,” says Aditya Bhonsale, MD, a cardiologist specializing in electrophysiology at the UPMC Heart and Vascular Institute in Pittsburgh. “There’s a dynamic component.” 

HRV is generally measured in milliseconds. In case you need a refresher, one millisecond is one-thousandth of a second—so we’re talking about very small differences here. You can feel your pulse and get a sense of whether your heart is beating quickly or slowly, but the minuscule differences in heart rate variability require special equipment to capture.

How Does Heart Rate Variability Work?

Your heart rate is governed by the balance of the sympathetic and parasympathetic nervous systems, explains Nino Isakadze, MD, a cardiac electrophysiology fellow at Johns Hopkins Medicine in Baltimore. These systems are part of the autonomic nervous system, which is responsible for regulating certain body systems that operate without your conscious control, including breathing and digestion. 

The sympathetic nervous system (SNS) produces the “flight or fight” response that you feel when you’re in physical danger, stressed by an unexpected meeting invite from your boss, or are startled by a jump scare in a horror movie. Your body shifts its energy to the areas necessary for an escape or confrontation, and your heart rate ramps up, your airways widen, your pupils get bigger, and your digestion slows down. 

By contrast, the parasympathetic nervous system (PSNS) produces the “rest and digest” response after the physical threat has passed, or you realize you’re not actually going to be fired, or the movie ends, relaxing your body. It slows your heart rate, increases digestive activity, and generally brings you back down to, and helps maintain, your body functions at baseline. Those systems work at different levels depending on what we’re doing, explains Christopher Tanayan, MD, a sports cardiologist at Lenox Hill Hospital in New York City. 

As the SNS and PSNS play off each other, the result is a very tiny variation in the length of time between heartbeats. The more efficiently the sympathetic nervous system can get revved up to adapt to stress or danger, and then the parasympathetic nervous system can ramp things down to normal when the need has passed, the better—and the higher the HRV. When the transition from one state to another is more sluggish and less responsive, HRV is lower. 

Why Does Heart Rate Variability Matter?

Studies have found that a lower HRV is associated with a higher risk of disease and death. Generally (but not always—more on that later) a high HRV is better than a low one.

Lower HRV is associated with a greater risk of a first-time cardiovascular event even among people without known cardiovascular disease, and also with depression and anxiety. A 2022 review and analysis of previous research found that lower HRV values were “significant predictors of higher mortality” across different age groups, sexes, continents, and more. So if there’s a change in your HRV, “that may be a sign that there’s a change in overall health,” Dr. Isakadze says.

Regular exercisers may also track their HRV to help guide their workouts. “Some athletes use it to determine whether they’re physically prepared for training that day,” Dr. Tanayan says. A lower HRV might mean they’re stressed, tired, ill, or otherwise not ready for a tough workout. And “for those who are fully ready to participate in sports, their HRV is higher,” he explains.

How to Measure HRV

It only became possible to detect and measure HRV with the invention of the electrocardiogram (also known as an ECG or EKG) in the late 1800s, which records electrical activity in the heart using wired sensors attached to your body. It lets physicians precisely measure the time between the same point in each heartbeat. To assess some heart conditions, patients can wear a heart monitor outside the doctor’s office for longer periods of time. But it’s still not a practical way for most people to regularly track their HRV, Dr. Isakadze says.

Wearable devices that gather health data, like smartwatches or chest straps, often use a different technology, called photoplethysmography. Those devices send a pulse of light through the skin to detect blood flow changes in the vessels beneath the skin. That measures your pulse, which can be taken as a surrogate for the heartbeat.  

“There’s ongoing research to understand how they perform compared to traditional ECG methods,” Dr. Bhonsale says. There are a lot of variables—including the specific technology being used, the population being studied, and how the device collects, interprets, and reports the data. But in general, studies suggest the measurements are acceptable, if not as precise as ECGs, he says.

Is There a ‘Good’ HRV Score? How About a ‘Bad’ One?

Unlike more accepted indicators of cardiac health like cholesterol levels or blood pressure, there are no guidelines on what makes a “good” or “bad” HRV from the American Heart Association or other health-focused organizations. Wearable device makers may publish their own charts based on data from their users, but those ranges don’t necessarily represent the general population. And there are so many factors that influence HRV that it’s hard to compare different people. 

The bottom line: “It’s personal,” Dr. Bhonsale says. “You can’t use someone else’s metrics—you have to track your own numbers.” Keep your eye on your HRV trends, not the specific number.

A woman checking her heart rate variability on her smartwatch while at the beach.

Luis Alvarez / DigitalVision via Getty Images

What Factors Affect Your HRV?

HRV changes naturally over the short and long term. Here are some of the top influences: 

  • Age: In general, HRV decreases with age, Dr. Tanayan says. A 2016 Journal of the American Heart Association study suggests that that’s due to the normal aging process rather than a result of increased health problems or medication use.

  • Biological sex: On average, females under 30 years old have a lower HRV than males. But at 30, that gap starts to narrow, and after age 50, it disappears, research suggests.

  • Illness: Illnesses, such as heart or lung problems, diabetes, and asthma, as well as minor viruses, can lower HRV. So can mental health issues such as depression and anxiety. But some heart problems, such as an irregular heartbeat (also called an arrhythmia), can cause high HRV—so a high HRV is not better in every case.

  • Time of day: It’s normal for HRV to fluctuate during the day, depending on what you’re doing. In general, HRV is higher at night, declining slowly before you wake up and then dropping more as you start your daytime activities. 

  • Weather and air quality: Hot weather seems to decrease HRV, while cold weather doesn’t have an effect. Certain types of pollution, especially fine particulate matter, may also lower HRV.

How to Increase HRV: 6 Solutions to Try

If your HRV has been trending lower and you want to improve it, there are some things you can do. But first, a big caveat: We don’t actually know whether changing your HRV in isolation will improve your health. 

“We know that people who lead a healthy lifestyle have a higher HRV,” Dr. Bhonsale says. “If you take a baseline and measure it over time, those with a higher HRV have a lower risk of death. If patients see that and make changes and increase their HRV, do they do better? That’s currently unclear.” There’s a ton of research going into HRV, though, thanks to the surge in wearable technology, its relatively low cost, and the fact that it doesn’t require an invasive test to measure. (Stay tuned.)

In the meantime, the great news is that the things you can do to raise your HRV are already known to be good for your cardiovascular and overall health. So, there’s no downside, and plenty of upsides, to doing them. Those strategies include:

1. Get Regular Exercise

Aerobic exercise is a great way to improve HRV. The biggest gains are probably most likely to come for people who go from not exercising at all to regular exercise, Dr. Bhonsale says. If you’re already a well-trained athlete, your HRV doesn’t have as far to improve. And if you exercise too much, you might overtrain and depress your HRV. 

2. Eat Healthfully 

Eating something akin to the Mediterranean diet—including lots of fruits and veggies, whole grains, fish, legumes, and nuts—has long been associated with better heart health. There’s also evidence it’s associated with a higher HRV. Meantime, eating a lot of saturated or trans fats, or high-glycemic carbs (the kind that are digested very quickly), has been tied to a lower HRV.

3. Get Enough Water

One study found that even mild dehydration resulted in lower HRV. According to the National Academy of Medicine, women need about 2.7 liters and men about 3.7 liters of water every day from both beverages and foods to meet their hydration needs. People who exercise more or are in hot climates need more. 

4. Don’t Drink Too Much Alcohol 

While a single alcoholic beverage didn’t affect HRV, two drinks decreased it by 28–33 percent, according to one study. Chronic drinking can also depress HRV

5. Get Enough Sleep

Since HRV tends to be higher at night when you’re sleeping, it’s important to make sure you’re getting plenty of good Zzzs. The standard recommendation for adults is seven to nine hours per night, though research suggests that when it comes to HRV, the quality of sleep may matter even more than the amount.

6. Try to Reduce Stress

When stress amps up your sympathetic nervous system, your HRV can decline. Stress reduction—even simple breathing exercisescan lead to a higher HRV. One study found that using a mindfulness meditation app for 10 days increased HRV both during the day and at night during sleep.

When to Talk to Your Doctor About HRV

HRV isn’t in the standard group of evidence-based health metrics like cholesterol levels or blood pressure. So, if you go to your physician with only the concern that your HRV is too low, they may not know what to do with that information. But you could bring it up in the context of any other signs and symptoms you’re experiencing. “It’s a good entry point for discussing your health concerns,” Dr. Tanayan says.

And remember: If you have a high HRV, it’s not a guarantee of good health. You shouldn’t ignore symptoms that may indicate heart problems, such as heart palpitations or chest pain, or any other symptoms that don’t feel quite right.

The Takeaway

Heart rate variability is an easy, noninvasive way to keep an eye on your health. If you track your HRV trends rather than getting caught up on the daily ups and downs, you may notice changes that indicate whether you’re headed in the right direction wellness-wise. “People get motivated by different things,” Dr. Bhonsale says. “If your HRV is higher, it may be a sign that you’re well-rested. If you have a low HRV, you may be stressed.” Tracking that over time can be an incentive to do the things you know are good for your heart—and your health.

This content is for informational and educational purposes only and does not constitute individualized advice. It is not intended to replace professional medical evaluation, diagnosis, or treatment. Seek the advice of your physician for questions you may have regarding your health or a medical condition. If you are having a medical emergency, call your physician or 911 immediately.


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