Heart rate variability: an objective measure of health
Heart rate variability (HRV) is the variation in time between
consecutive heartbeats. Each time our heart beats, there is a variation in time
between each beat. It does not (or should not) beat in a consistent rhythm. In
fact, research shows that a higher HRV is associated with better health.
HRV is a measure of the responsiveness of our autonomic
nervous system (ANS). The ANS is a part of our peripheral nervous system that
regulates involuntary physiological processes such as our heart rate, blood
pressure, breathing, and digestion. More specifically, HRV is a measure of the balance
between two parts of our ANS; the parasympathetic and sympathetic nervous
systems [1].
Our sympathetic nervous system (SNS) is associated with our
“fight or flight” response. This is a state of increased activity comprising increases
in blood pressure, heart rate, and glucose production, and a slowing in our digestion.
Activation of our parasympathetic nervous system (PNS) is associated with “rest
and digestion” comprising a slowing in our heart rate, decrease in blood
pressure, and an increase in certain digestive processes. The balance between
our SNS and PNS is important. Overactivity in one of these systems can impair
both mental and physical health. Unfortunately, for many people, particularly those
with depression and anxiety, there is an overdominance in the SNS. As stated
earlier, HRV is a measure of the balance between our PNS and SNS. A higher HRV,
which is associated with an increased PNS is a marker of good health. A higher
HRV is also a marker of increased activity in our vagus nerve. This is our
longest cranial nerve that is connected to our gut, liver, heart, and lungs.
Increasing the activity of our vagus nerve is associated with improvements in
many physical and mental conditions. For example, vagus nerve stimulation is an
effective treatment for epilepsy, treatment-resistant depression, and migraine
[2].
There is increasing research suggesting HRV can be used as an objective measure of health. HRV tends to decrease as we age, is higher in fitter people, and those living a healthier lifestyle. HRV is also strongly correlated with levels of inflammation in the body. In people with cardiovascular disease or people who have experienced a myocardial infarction, a lower HRV is associated with an increased risk of mortality. HRV is also lower in people with depression, post-traumatic stress disorder, burnout syndrome, and is lowered during times of stress. People with higher HRV have been shown to have a better cancer prognosis and disease progression. Overall, HRV can be an objective measure of stress [4-8].
HRV is traditionally measured using an electrocardiogram
(EEG). However, there are devices on the market that can also measure HRV with
varying levels of reliability. These include finger sensors and Polar chest
straps. There are also apps on our phone and watches that can also measure HRV,
although the reliability of these is disputed. Devices such as HeartMath are specifically
designed to measure HRV. Heartmath is an intervention that teaches people ways (through
controlled breathing) to increase HRV.
Here are some natural ways to increase HRV/ Vagus nerve
activity
- Slow, controlled breathing
- Relaxation practice
- Biofeedback
- Meditation
- Yoga
- Massage
- Exercise and increasing overall fitness
- Eating a healthier diet. The foods we eat can affect HRV and generally eating a healthier diet (e.g., Mediterranean diet) can increase HRV. Fasting and caloric restriction can affect HRV [9,10]
- Increase omega-3 polyunsaturated acids (e.g., fish oils) [11]
- Ensure good vitamin and mineral status. There is some research showing low vitamin D, vitamin B12, magnesium, and iron are associated with lower HRV [12-15]
- Probiotics. This has been shown in animal studies but no human studies so far [16]
- Herbs/spices such as curcumin and saffron [17-18]
- Listening to music particularly classical music
- Laughing
- Gargling and triggering your gag reflex. However, I am not convinced by the long-term effects of these and how many people can (or are) willing to do these regularly.
Given the association between HRV and improved mental and
physical health, implementing ways to increase it are likely important. More
research needs to be conducted in the area but HRV also presents as a promising
objective measure of health.
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References
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