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Heart Rate Variability; A Key Health Metric

by | Jul 4, 2021

What if we had an hourglass that could predictably tell us how much time we have left in life?  What if we could adjust the flow of the sand to slow it down and hence, increase our remaining time?  Heart rate variability is a physiologic metric that is like peering into the hourglass of your life.  How fast is the flow of the sand?  The higher the heart rate variability (HRV), the slower the flow of the sand through the hourglass.  The lower the HRV, the faster the flow of the sand through the hourglass.  To increase our longevity, we use monitors to help up focus upon tracking and increasing our HRV.  Naturally, as we age, our HRV decreases.  Studies have shown, however, that we can increase our HRV by changing our habits.  Physicians can monitor HRV through remote patient monitoring.


HRV is a measurement that is different from our pulse rate.  The pulse rate measures the number of heart beasts in a minute.  Your pulse rate has within it, a dynamic process with small differences between each heartbeat.  Each heart beat is the large wave on the EKG monitor.  These are called the R waves.  There is a slight variation between each wave, this measurement is called the R interval (see Figure 1).  These variations are controlled by our nervous system.  Hence, HRV provides information about the functioning of the nervous system’s control on the heart rate and the heart’s ability to respond.  In turn, this gives us a very accurate evaluation of your state of health.

Figure 1:  Visual representation of the R-R interval in an EKG with the heart rate variability measurement. (Reproduced from Firstbeat.)


The nervous system is made up of two opposing parts.  The sympathetic and parasympathetic nervous system.  The sympathetic nervous system is the “fight or flight” nervous system that regulates our heart rhythm during times of stress either emotional stress or physical stress.  The parasympathetic nervous system is the relaxation system that helps the body recover from stress and digest food.  A good balance between the two systems is essential to good health.  In good health, we expect to see wider variations between the R interval.  The R interval should widen during times of relaxation and it should narrow during times of stress.  Too much stress or sympathetic response, and there is a more narrow R interval.  Overtime, this lowers the HRV.  Certain disease such as diabetes can affect the parasympathetic nervous system, thereby increasing the body/s response to the sympathetic system.


The EKG is the gold standard method to measure HRV.  However, it is not feasible to carry around an EKG machine.  Alternatives include remote monitoring devices that can measure variability from the wrist, chest or finger.  The wrist devices include Apple watch devices, the Whoop device, Fitbit, Polar and Garmin among others.  Wristbands can be loose at times which would lessen accuracy of the readings.  For those who are serious about accurate HRV measurements, the chest bands and the Oura ring provide more accurate readings.  Chest band heart rate monitors include the Polar H10 chest strap and Garmin Chest Strap Heart Rate Monitor.  These monitors provide more accurate measurements, but require wearing a strap around your chest.   This may not be convenient for all.  The Oura ring is the most portable and convenient, least intrusive monitor for heart rate variability.  Hospital measures the pulse rate with a finger device.  That is because the vessels are closer to the surface at the fingers.  Oura rings are also fitted to ensure accurate readings.  Overnight readings while sleeping provide the most accurate readings, for those who typically charge their wrist devices at night, this can be a hindrance as well.


If a greater HRV means a longer life, it seems reasonable to focus upon ways to increase your HRV.  An HRV over 50 is considered healthy.  However, even elite athletes monitor and work to improve their HRV level to improve performance.  You can change your heart rate variability through changing your health behavior.  Heart rate variability decreases from physical stress such as manual labor, chemical stress such as poor nutrition and mental stress from relationships and work deadlines.  Exercise causes a temporary decrease in HRV, that later increases following the recovery.  The higher a person’s average heart rate variability, the less vulnerable they are to these stressors


There are studies that support the use of HRV as a marker for population health.  Through utilization of HRV measurements, healthcare providers can evaluate real time response to preventive therapies and the effectiveness of health behavior change.  A population that shows increasing HRV is a population that is moving in a positive director towards greater health.  This in turn reflects decreased healthcare expenditures.

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