If you have a smartwatch, you might have noticed a metric called heart rate variability (HRV). HRV is a relatively new measurement that many people aren’t aware of. But, paying attention to your HRV is a good thing.
Heart rate variability can provide a lot of insight into your physical and mental health. It can also reveal a lot about your sleep.
What is Heart Rate Variability (HRV)?
Heart rate variability simply refers to the variability in time between each heartbeat. It might feel as though your heart beats at a steady rate. But, the time between heartbeats actually varies. For instance, your heart rate might be 60 beats per minute. But your heart doesn’t exactly beat at one heartbeat per minute. Sometimes it beats at .8 seconds and other times it's 1.2 seconds. That’s the difference or variability in your heart rate.
Your heart rate variability is controlled by your autonomic nervous system (ANS). Two parts of the autonomic nervous system are involved in HRV.
- Sympathetic nervous system (SNS) - This part of the nervous system is responsible for your fight or flight response. This response is what makes your heart beat out of your chest when you almost crash into another car. When you’re in fight-or-flight mode, your heart rate increases. The time between beats becomes shorter. This lowers your HRV.
- Parasympathetic nervous system (PSNS) - The job of your PSNS is to relax your body. It slows down your heart rate and returns your body to baseline after a stressful event. When your PSNS is activated, it increases your heart rate variability.
A number of factors can influence your autonomic nervous system and affect your HRV including sleeping patterns, physical activities, and stress levels.
How to Measure HRV
Heart rate variability is typically measured with an electrocardiogram (EKG or ECG). However, some newer wearable devices can measure heart rate variability.
What is a Normal HRV?
Heart rate variability is typically recorded in milliseconds. Research suggests that healthy adults have a range HRV of 19-75 milliseconds. The mean HRV is 42 milliseconds for adults. In general, HRV decreases with age.
The best way to monitor your HRV is to pay attention to your specific number. Look at overall trends or changes in your number over a period of time.
HRV and Your Health
Your HRV is an indication of how much stress your body is under. Generally, higher HRV levels are optimal. When you have higher HRV, your body is able to calm down more easily and quickly once stressed. A higher HRV is also associated with better cardiovascular fitness.
When your body is unable to manage the stress that it is under, your HRV will likely be low. So, if you are dealing with chronic stress or depression, you might have a lower HRV.
A lower HRV is also linked to physical health problems. A study, conducted by the American Heart Association, found that a lower nighttime heart rate variability is a strong predictor of stroke. It also increases the risk of heart attack and sudden cardiac arrest.
What HRV Reveals About Your Sleep
You want to see a high HRV during sleep. If you consistently have low HRV during sleep, it means that your body is stressed during sleep. Studies have found that a low sleep HRV is associated with sleep disorders.
A systematic review of the literature found lower HRV scores among those with sleep disorders compared to those without sleep problems. People with severe obstructive sleep apnea have significantly lower HRV scores.
HRV scores are also linked with general sleep quality even if you don’t have a sleep disorder. One study examined the effect of HRV on sleep quality and duration. Participants included 260 university hospital staff in Iran. Poor sleep quality was associated with a lower HRV.
Another study examined the association between sleep efficiency and heart rate variability in 39 healthy volunteers. HRV scores were taken in the daytime. The researchers found that greater HRV is associated with better sleep efficiency at night.
How to Improve Heart Rate Variability
There are ways to increase your heart rate variability. To improve this number, try to decrease your overall stress level. Also, try these tips:
- Treat sleep disorders - Because of the association between sleep disorders and HRV, it’s important to see a sleep specialist to treat possible sleep disorders like obstructive sleep apnea and insomnia.
- Adopt a healthy diet - Research has found a link between heart rate variability and diet. The Mediterranean diet for example, is associated with a higher HRV. This diet consists of vegetables, nuts, fruits, whole grains, and herbs. If you want to lower your HRV, stay away from high amounts of carbohydrates, saturated and trans fats. These are linked with lower HRV numbers.
- Improve your sleep hygiene - Insomnia is linked to a lower HRV. Poor sleep hygiene can contribute to insomnia. Ways to improve sleep hygiene include keeping the same sleep schedule every night, relaxing before bed, and maintaining a bedroom temperature that is conducive to sleep (between 60-67 degrees Fahrenheit or 15 to 20 degrees Celcius).
- Practice meditation and other stress-reduction techniques - This can help decrease the fight or flight response. You can try any number of exercises, including journaling, sleep stories, or listening to music.
- Try to get some form of movement everyday - Exercise is associated with a lower HRV. The Centers for Disease Control and Prevention (CDC) recommends 20-25 minutes a day.
- Spend time outdoors when possible - Nature has been found to decrease stress levels and reduce anxiety. Lowering your stress can help improve your HRV.
- Cut down on alcohol use - Studies have found that moderate to heavy alcohol consumption is linked with a decreased HRV. Besides affecting your HRV, excessive alcohol use is detrimental to your sleep and overall health. Therefore, try cutting back on the amount you drink. You can try substituting alcohol for other drinks or gradully reduce how mcuh you drink every day.
Heart rate variability is an important metric that you should pay attention to — if you are not already. It can offer a glimpse into your emotional and physical health, as well as your sleep. If you notice that yours is trending low, take the step above to improve it.
