Heart Rate Variability (HRV) – Your “Immunity Booster”

The link between the autonomic nervous system and immunity / How heart rate variability can be used to detect and prevent disease

Autumn and winter are peak seasons for infectious diseases. Our immune system is challenged by decreasing temperatures and wet weather, and the common cold, flu, and further threats to our health are gaining ground. More time spent inside, with other people around, adds to those risks. The current pandemic illustrates this seasonal trend, with various countries stepping up measures to control rising incidence. Let’s take a closer look at how we can take control of our immune status by measuring heart rate variability (HRV), and provide support to our physicians.

There is extensive communication between our immune system and our nervous system, experts explain. This includes the “hardwiring” of sympathetic and parasympathetic nerves to lymphoid organs – in particular red bone marrow, in which blood and immune cells are produced, and the thymus, where T-lymphocytes mature.

The sympathetic nervous system (SNS, which is responsible for “fight or flight”) and the parasympathetic nervous system (PNS, responsible for “rest and digest”) are the components of the autonomic nervous system (ANS). The ANS is critical in regulating processes required for maintaining physiological homeostasis and responding to acute stressors. Recently, researchers have been studying potential further functions of the ANS: it appears to play an essential role in regulating, integrating, and orchestrating processes between diverse physiological systems.

The modulators of immune activity

Neurotransmitters such as acetylcholine, norepinephrine, vasoactive intestinal peptide, substance P and histamine modulate immune activity. Neurotransmitters, often called the body’s chemical messengers, are molecules used by the nervous system to transmit messages between neurons, or from neurons to muscles.

Central autonomic neural networks are informed of the peripheral immune status via neural and non-neural communicating pathways. While the immune system interacts directly within brain regions that regulate autonomic function, the autonomic nervous system innervates organs that contain immune cells, such as the spleen and bone marrow. Cytokines and other immune factors affect the level of activity and responsivity of discharges in sympathetic and parasympathetic nerves innervating diverse targets.

Heart rate variability (HRV) – biomarker of health

This is where heart rate variability (HRV) comes in. HRV biofeedback (HRVB) allows for measuring the autonomic function, with a host of applications for a variety of conditions.

In the context of immunity, the relation between HRV and inflammatory states has been extensively studied: for example, a meta-analysis of over 51 studies with a total of 2,238 patients demonstrated an inverse relationship between HRV and inflammation. While the precise mechanism of how the immune system and the ANS interact to impact the HRV may still have to be described, the common measure of HRV, the standard deviation of the interval between heartbeats (SDNN), is a viable indicator for monitoring the immune state. SDNN has been shown to correlate inversely with the nonspecific inflammatory marker C-reactive protein (CRP).

For measuring HRV, readily accessible, easy-to-use technology is available. A smartphone camera is the only device required. Its flash illuminates the fingertip, making changes in the blood vessels, which occur due to the natural heartbeat, visible for analysis. When blood is pumped through the vessels, they appear darker; blood being pumped out leads to lighter vessels. Based on these changes the heartbeat is analyzed, and the HRV is determined, providing the basis for computing further vital data indexes.

In the context of the immune system, this approach allows for the improved self-management of our health, and it provides significant support for physicians in diagnosing and monitoring their patients.