The heart rate variability (HRV) is an important biomarker for cardiovascular health and autonomic nervous system balance. Like many other biomarkers, HRV is very sensitive to change, even the slightest amount of stress can cause fluctuations. Because of its sensitivity, heart rate variability can be a very useful index to tell us how our bodies are doing, especially during the COVID-19 pandemic.
A Review of COVID-19
COVID-19, or coronavirus, is an infectious illness that primarily attacks the respiratory system. However, scientists and researchers all over the world are seeing the virus attack more than just the lungs; we are seeing its harmful effects on every body system. With the number of cases increasing every day and a vaccine far away, it becomes our collective responsibility to monitor our own symptoms and do our part of slowing the spread.
Part of the reason why COVID-19 is such a deadly disease is that it has a very long incubation period of 14 days. This means it can take up to 14 days after exposure for symptoms to begin to show. Because of this, many people unknowingly become carriers, assuming that their lack of symptoms equates to being coronavirus-free.
This is the reason why biomarkers are so important. Biomarkers for COVID-19 are specific signals that can tell us that we might have contracted the virus. These biomarkers are often detected before major symptoms begin to show, lowering the chances of the disease being spread further.
Heart Rate Variability as a Biomarker
Preliminary research has shown that HRV can be a biomarker for COVID-19. Because HRV is a quantifiable measure of our body’s condition, being under stress will cause a decrease in HRV. If you contract the virus but have yet to see the symptoms of fever, chills, or congestion, that does not mean your body isn’t reacting to the virus. While you may not have any outward symptoms, one of the first indicators of your immune system fighting can be heart rate variability. When your body experiences inflammation as a result of the infection, your organ systems begin to work to eradicate the virus and protect your body. The vagus nerve plays an important role in regulating your body’s inflammatory response, and its activity is reflected by HRV¹. Research has seen an overactive vagus nerve causing a decrease in HRV, meaning a sudden drop in HRV could be a sign of your immune system fighting off infection².
C-Reactive Protein Biomarker
Another biomarker for COVID-19 is the C-reactive protein (CRP)³, produced by the liver. Research has seen an increase in CRP levels when your body is fighting infection and experiencing inflammation⁴. A study in Wuhan, China saw patients suffering from severe cases of COVID-19 had significantly higher levels of CRP when compared to those with mild symptoms⁵. However, the only way to determine if you have elevated levels of CRP is to have a blood test done. But how does this help us at home? The connection lies between the correlation between CRP and HRV.
Research has shown that CRP levels are inversely related to HRV⁶, meaning that an elevated CRP level and a lowered HRV are associated. The reason for this relationship is suggested to be a decrease in the autonomic nervous system’s activity when the body is having an immune response⁷.
In short, preliminary research has shown that a sudden drop in HRV can be an indicator of COVID-19. However, much of this research is extremely new and has not been subject to the same peer-review rigor yet, so remember to take this all with a grain of salt.
Monitoring HRV levels can be a preemptive sign to look out for, and if you see numbers that cause concern, always err on the side of safety by self-quarantining and having an official test administered.
Pavlov, V. A., & Tracey, K. J. (2012). The vagus nerve and the inflammatory reflex — linking immunity and metabolism. Nature Reviews: Endocrinology, 8(12), 743–754. doi.org/10.1038/nrendo.2012.189.
Pavlov and Tracey (2012).
COVID-19 — A systematic review. Life Sciences, 254, 117788.doi.org/10.1016/j.lfs.2020.117788.
Weiping Ji, Gautam Bishnu, Zhenzhai Cai, Xian Shen. medRxiv, 2020.03.10.20033613; doi.org/10.1101/2020.03.10.20033613.
Kermali et al. (2020).
Saito, I. et al. (2016) Impact of heart rate variability on C-reactive protein concentrations in Japanese adult nonsmokers: The Toon Health Study, Atherosclerosis. doi.org/10.1016/j.atherosclerosis.2015.10.112.
Saito et al. (2016)