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.
How apps improve the management of chronic diseases, including diabetes
Noncommunicable chronic diseases, including cardiovascular disease, diabetes, and mental health conditions, were responsible for almost 70% of deaths worldwide in 2016. This is an estimate from The World Health Organization (WHO). The prevalence of these illnesses is increasing globally, leading to major social and economic consequences. The U.S. is a prime example: research by the American Action Forum (AAF) from September 2020 shows that chronic conditions in the country – already highly prevalent – are expected to rise over the next several decades among all age groups. The AAF calculates that, including indirect costs associated with lost economic productivity, the total cost of chronic disease in the United States reaches US-D 3.7 trillion each year, approximately 19.6 percent of the gross domestic product. Experts agree that action needs to be taken to reduce health care costs and improve patient wellbeing – and quality and effectiveness of disease management play a major role.
To better manage chronic diseases is key
Chronic diseases are generally linked to an imbalance of the autonomous nervous system (ANS). This results in sympathetic overstimulation and a lack of activity of the vagus nerve, a fundamental component of the parasympathetic branch of the ANS. This phenomenon, called dysautonomia, can both be a consequence of chronic disease as well as a key risk factor in its development. The study by Zalewski et al. emphasizes that ANS dysfunctions should be considered at each stage of the diagnostic and treatment processes. The identification of changes in vagal activity holds the key regarding the management, and detection, of chronic conditions.
Heart rate variability – biomarker of health
This is where heart rate variability (HRV) comes in. Heart rate variability biofeedback (HRVB) allows for the indexing of the autonomic function. Whereas high HRV reflects the ability of the cardiac system to adapt to intrinsic and extrinsic changes (e.g., stress), low HRV is an indicator of risk for cardiovascular morbidity and mortality. A systematic literature analysis by Shaffer et al. showed the feasibility of HRVB in chronic patients; significant positive effects were found in various patient profiles. Researchers concluded that heart rate variability biofeedback could be effective in managing patients with chronic conditions, including diabetes.
kenkou has developed a technology that enables vital data measurement (including HRVB) using just the smartphone camera. This readily accessible, easy-to-use technology serves to enhance treatment and detection of chronic conditions.
Why is measuring mental well-being becoming critical and how can we make it as simple as checking temperature?
Loneliness, stress, anxiety, and depression: the COVID-19 pandemic has been severely impacting our lives. Health challenges affecting ourselves or our loved ones can cause strong emotions, and public health actions such as social distancing can make us feel isolated. The pandemic intensifies mental health challenges that were widespread already before the crisis.
Loneliness, as an example, is not just a painful experience we may go through. It is worse for us than smoking, more harmful than obesity, and it comes with a risk of premature mortality. In the UK, for example, the surging number of lonely people and how feeling alone harms us was presented by a pre-pandemic report by the Jo Cox Commission on Loneliness. According to Making Caring Common, a project of the Harvard Graduate School of Education, 36% of all Americans feel “serious loneliness.”
The World Health Organization raises the alarm: Approximately 280 million people in the world have depression. Survey conducted by The Centers for Disease Control and Prevention (CDC) among adults aged ≥18 years across the United States in June 2020 suggests that 40.9% of respondents reported at least one adverse mental or behavioral health condition, including symptoms of anxiety disorder or depressive disorder (30.9%). The waiting lists for psychotherapy are getting longer. “With anxiety and depression on the rise during the pandemic, it has been challenging for people to get the help they need” – writes The New York Times in a recently published article.
These examples illustrate the scope of the issue and the need to support therapy when qualified help is hard to find.
Untapped power of HRV
In light of this high incidence of risk factors and conditions and lack of professional staff to address for help, what can individuals do to find out if they are at risk? Whereas a panic attack may be easy to identify, the slow rise in blood pressure or inflammation is difficult to notice. In this context, heart rate variability (HRV) comes into play. It is a promising biomarker of mental health resilience (MHR).
MHR influences mental well-being and vulnerability to psychiatric disorders. Whereas conventional measurement of resilience is based on subjective reports, HRV can act as an objective biological, physiological biomarker. A study published in the Journal of Affective Disorders showed that HRV might indeed serve as a global index of an individual’s flexibility and adaptability to stressors.
Effective therapy is available, but simple methods of diagnosis are lacking
Cognitive Behavioral Therapy (CBT) is the most widely-used therapy for a wide variety of mental health disorders. Research has shown it to be effective in treating panic disorders, phobias, social anxiety disorder, and generalized anxiety disorder, among many other conditions. CBT is a “talking therapy” that can help individuals manage their problems by changing the way they think and behave. The therapy aims to help individuals deal with overwhelming problems in a more positive way by breaking them down into smaller parts. CBT is based on the concept that one’s thoughts, feelings, physical sensations, and actions are interconnected, and that negative thoughts and feelings can trap individuals in a vicious cycle.
However, a diagnosis is needed to begin CBT, and this is not always easily available. Accurate tracking of selected biomarkers including HRV can be a game-changer.
As a noninvasive and easily applicable biomarker of MHR in real-life contexts, HRV allows for accurate stress level measurements for CBT. It helps in tracking recovery by identifying the change in behavioral patterns and treatment progress over time. In addition, it serves as an index of cognitive and affective self-regulation. Whereas negative emotions are related to reduced HRV and incoherent heart rhythm patterns, cardiac coherence refers to a high amplitude sinus-like heart rhythm that is characterized by increased vagal activity. This is associated with a psychological state of positive emotion.
HRV biofeedback (HRVB) devices display heart rhythms in real-time. They can be used to teach patients to generate coherent oscillations in the heart rate. A combination of CBT and HRV biofeedback training can help reduce anxiety symptoms while increasing HRV and the ability to sustain cardiac coherence.
When properly applied, digital technologies may prove to be groundbreaking in addressing the problem of early diagnosis and treatment of selected mental illnesses.
Technology developed by kenkou for precision biofeedback
kenkou – a Berlin based startup founded in 2014 – is developing technologies that can revolutionize mobile health and vital-data measurement worldwide. Together with a team of data scientists, the company is exploring the power of HRV in mental health tracking.
The time interval between the heartbeats of a healthy heart is constantly fluctuating. It indicates how well your body handles stress. Intervals over a given time period are referred to as HRV. A high HRV indicates that your body can cope well with stress, whereas a low HRV can be a symptom of fatigue, stress, or even illness. There are many values that can be used to measure HRV, including RMSSD and PNN50.
RMSSD (Root Mean Square of Successive Differences) shows how well an individual’s body is recovering from stress and reflects how well the parasympathetic nervous system can help it to regenerate and recover. A high level of stress relief is partly due to a high RMSSD.
PNN50 (correlated with Parasympathetic Nervous System activity) is the fraction of consecutive heartbeats with an interval greater than 50 milliseconds between them. A higher PNN50 value shows that an individual’s heart rate has drastically changed within a brief time period. For healthy individuals aged 25-74 years, the range is -3% to 43%.
Respiratory Sinus Arrhythmia (RSA) Amplitude, sometimes referred to as the HRV amplitude, is the change of heart rate believed to be caused by breathing. Kenkou measures it by breaking up measurements into sections that match the expected breathing interval of the user – ten seconds in length –, calculating the difference between the maximum and minimum heart rates and averaging the results found for each of the sections.
kenkou computes a spectrum of indexes. This includes the Tension Index: this heart rate index is determined by the heart rate variability and is an objective indication of how much stress and tension there is in the body. Recovery Ability is related to an individual’s relaxation ability; it is measured by the parasympathetic nervous system, which controls the body while at rest. The easier it is for the body to calm down, the higher its stress resilience.
How do we make vital signs checkup as simple as possible, accessible to everyone?
kenkou’s team has developed a technology that enables vital signs measurement (including HRV) using just the smartphone camera. Its flash illuminates the fingertip, making changes in the blood vessels, which occur due to the natural heartbeat, visible for analysis. For example, 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 detected, the data is analyzed, and the HRV is determined, providing the basis for computing further vital data indexes.
Readily accessible, easy-to-use technology from kenkou enhances treatment of mental health challenges in the pandemic and beyond. The company’s software development kit (SDK) enables cardiovascular vital signs analysis through third-party applications in the digital health and well-being industry as well as for insurance and pharmaceutical companies.
Can we avoid cardiovascular disease by regular monitoring our heart rate variability? How can on-time regular HRV measuring help to detect CVDs?
Did you know that cardiovascular diseases, or CVDs, are the leading causes of death and morbidity in industrialized nations, accounting for 32% of all deaths? It is the unfortunate truth, that despite the major advancements in healthcare accessibility, technology and improved medical treatments over the last decades, the frequency of cardiovascular conditions as well as the associated mortality rates continue to increase. The risk of developing CVDs also rises with age, and patients who suffer from CVDs often require chronic or recurrent hospitalization and long-term medical treatment, with all the costs that this implies for the healthcare systems.
There is a strong link between heart health and heart rate variability (HRV), as well as the value of the latter as a direct indicator of autonomic nervous system (ANS) disbalance. Let us explain what each of these terms means. HRV represents the variability in the time intervals between successive heartbeats while ANS is responsible for key physiological functions in the body, including cardiovascular activity. It regulates heart contractions and heartbeat, as well as blood pressure, which explains its essential role in maintaining cardiovascular functioning and health.
The amount of currently available research on the relationship between CVD and unbalanced sympathetic-vagal outflow to the heart confirms the important influence of the ANS on cardiovascular health. HRV is an established marker of how both branches of ANS (sympathetic and parasympathetic) work. Tracking HRV levels can play a key role in understanding cardiovascular risk factors, as well as the onset of the cardiovascular disease itself.
Today, HRV is an acknowledged index for cardiovascular science and diagnostics. It has become a standard non-invasive metric for evaluating the autonomic nervous system, serving as a convenient and relatively cheap tool for ANS function assessment and tracking. This has led to an increase in the development of devices that can track HRV levels, like smartphone-integrated apps and tools, or wearable devices. Available to the vast population, such consumer tools can have an exceptional impact on HRV monitoring, cardiovascular disease diagnostics and care.
HRV serves as an indicator of the activity levels of the sympathetic and the parasympathetic branches of the ANS, as well as of the way these two branches modulate together the heart activity. A high HRV is a sign that the heart is operating well, and that it adapts to various stressors quickly and efficiently. In contrast, a low HRV can be an indicator of reduced cardiovascular fitness and of too much stress, when the sympathetic nervous system is constantly activated. Dysfunction of the ANS plays a major role in the development and progression of cardiovascular diseases, including myocardial infarction, heart failure, and sudden cardiac death.
In normal conditions, HRV values are constantly fluctuating throughout the day, as they are highly dependent on the interaction between the two branches of the ANS – sympathetic and parasympathetic. When the body is under stress, the sympathetic branch promotes the release of stress hormones, putting the body in the “fight-or-flight” mode. On the other hand, the parasympathetic branch is activated during more relaxed and less stressful times, turning on the “rest-and-digest” mode. When the sympathetic branch is strongly activated HRV values are low. A low resting HRV can serve in certain cases also as an indicator of cardiovascular risk factors, along with others, such as unhealthy lifestyle habits (like a sedentary lifestyle) and additional health conditions (like diabetes).
It is already well known that patients who exhibit low HRV levels following a CVD-related event (e.g. heart attack) have a more difficult recovery process and higher mortality risk. Therefore, tracking HRV levels can help not only to detect the early onset of CVD but also serve as a prognostic factor for patients with ongoing or past CVD conditions.
From a preventive perspective, routine HRV monitoring is meaningful also for individuals who had no previous history of cardiovascular conditions. Research shows that individuals who show fewer fluctuations in the heart rate and exhibit enhanced HRV values are overall healthier. In these individuals, a sudden change in the HRV values can act as an immediate and direct indicator of declining health status.
In general, a low HRV usually means that the sympathetic branch of the ANS is dominating and preparing the heart and the body to take on more stress than normal, which makes the heart beat faster and with less variability.
However, in cases of strenuous exercise, a decreased HRV is not a bad sign, but only an indicator that the body is dealing with physical exertion. In this case, ANS signals to the heart that the focus should be turned to uttermost parts of the body rather than internal processes.
Impact of HRV metrics on CVD detection
HRV is one of the most informative indicators of risks linked to cardiovascular disease and therefore, received a lot of attention in the last couple of years. New methods for both tracking and analyzing HRV metrics are being developed to offer healthcare providers a convenient and easily accessible method of detecting and monitoring various health conditions. The final goal is to alleviate the burden on the healthcare system by bringing heart health tracking methods closer to actual patients and raising their awareness about CVD risk factors.
In the last decade, thanks to automated analysis methods, HRV has become a regular part of the routine examination of patients with cardiovascular risks and chronic cardiovascular disease. HRV represents a useful tool for documenting events in various clinical settings, and remarkably low HRV measurements have been clearly linked to the severity of CVD, additionally proving how strong HRV and CVD correlate.
HRV could therefore become a valuable tool for assessing the health of the general population, as well as offer a method for detecting risk factors for cardiovascular disease. Previous studies did prove that HRV measurements can be used to predict increased mortality risk in patients who suffered from a heart attack or heart failure. However, the research available today on the link between HRV, ANS and CVD is still partial, and requires further studies before tools for CVD risk factors can be derived and fully accepted.
24h-long monitoring is considered to be the optimal length for reliably tracking the changes in HRV metrics. Usually, such long measurements are performed with special ECG devices. However, given the time that such monitoring duration requires, other approaches need to be considered and developed. Particularly, using a smartphone or another wearable device to measure HRV in shorter or selected intervals throughout the day. It is a desirable alternative that is much more convenient and economical and delivers long-term measurement benefits.
Furthermore, the onset of cardiovascular disease can be the result of a combination of various factors, which must always be taken into consideration. HRV, therefore, should not be treated as an exclusive indicator of heart-related health issues, but rather as a valuable addition and a convenient tool for monitoring the efficiency of cardiovascular regulation.
HRV metrics need to be smartly integrated with the existing tools for identifying, tracking, and quantifying risk factors of CVD. However, an overestimation of the HRV as a predictor for lifetime risk of CVD should be avoided. Nevertheless, in combination with regular and specific checkups with medical professionals, HRV has immense potential in helping the general population take better care of their health and build lifestyle habits that enhance both life expectancy and quality
Which is better for heart rate monitoring: ECG or PPG? How to measure heart rate variability in most accurately.
The heart is a complex organ. Apart from continuously pumping blood over an entire human lifespan, the heart provides valuable insights into the general state of different processes in the body. Monitoring the heart enables a wide range of mental, emotional, and physical health assessments, like stress management capability or the state of mental and cardiovascular health. Finding new ways to monitor the heart can help detect the early onset of cardiovascular disease, which shows the potential for preventive health. Heart rate variability (HRV) is the most valuable metric for assessing how the autonomic nervous system (ANS).
The contraction activity of the heart muscle relies on electrical impulses and is strongly regulated by the autonomic nervous system (ANS). The ANS controls many body functions through the interchangeable activity of its two branches: sympathetic and parasympathetic. Heart rate variability (HRV) assesses how the body’s capability to take on and manage stress. As a measuring unit of the variability between heart beats, HRV directly indicates how the ANS is functioning.
Modern technology and advancements in the field of medical devices offer new methodological possibilities for non-invasive HRV tracking. The most widely used sensor-based technologies are ECG (electrocardiography) and PPG (photoplethysmography). For those who are looking for the best HRV detection technology to include in apps for wearable devices, this article will outline the similarities and differences between the two, as well as point out the advantages and limitations each of these methods, bring to HRV measuring.
ECG for HRV recording
Short for electrocardiography, ECG measures the electrical activity of the heart over a period of time through electrodes that are attached to the skin. ECG essentially records the electrical activity of the heart muscle and how it is affected by different factors like the activity of the ANS. It records signals that happen far from the skin’s surface, which ECG electrodes capture instantly and accurately. This makes ECG a non-invasive method for measuring HRV and it is used as the reference standard diagnostic test by many healthcare providers who assess cardiac health.
The result of an ECG reading is called an electrocardiogram, and its most relevant feature for analyzing HRV is called the QRS complex: a graphical hallmark of the heart’s periodic electrical and contractile activity. Algorithms use the time interval between successive R waves to measure the duration of a heartbeat and calculate HRV values, which make ECG a highly accurate, robust, and sensitive method of measuring HRV. This also means that a substantial reading can be accurately accomplished in a short time frame (e.g. < 5 minutes) as well as during a wider range of activities (e.g. a 24h ECG recorded during habitual daily movements).
PPG for HRV recording
PPG (short for photoplethysmography) is a very simple optical technique for measuring HRV. Unlike ECG, which uses electrodes, PPG applies light reflection to detect the blood volume changes in peripheral arteries which occur with each heartbeat. Recordings are usually measured on parts of the body where blood vessels are close to the skin, like fingertips or earlobes. The recorded pulse waveforms are the basis for measuring HRV through PPG.
Advantages and limitations
Readings obtained through the ECG method have proven to be more accurate and comprehensive than those obtained through PPG. This is mainly because ECG reads the electrical signals produced by the heart activity directly, while PPG provides a more indirect measurement, using light reflection to detect the pulsating activity of the heart. When it comes to ease and accuracy of measuring, PPG can be measured at several positions on the body and offers a wide range of measurement possibilities, while ECG requires more specific anatomical placement of electrodes on the body.
PPG measurements are influenced by the number and proximity of the blood vessels present on the placement spot, which makes the accuracy of PPG change according to the body position. The accuracy of PPG also depends on external factors, like the effect of ambience lighting and in some cases even motion factors. This means that PPG could become less accurate in measuring HRV during exercise and may require additional data processing steps to improve accuracy under challenging conditions.
ECG can produce accurate data faster and in a more direct way than PPG, as it includes electrical readings and does not require settling time. However, ECG also introduces several challenges related to the collection and interpretation of data, as it relies on a physician to be prescribed, performed, and interpreted. This greatly limits access to this tool for diagnosis, care, prevention, or general HRV tracking. An interesting finding is that comparing 5-minute readings from both methods indicated a very high degree of correlation between ECG and PPG as methods for measuring HRV.
Conclusion
ECG and PPG represent two different approaches to measuring HRV in a fast, convenient, and accurate manner. Studies show that PPG is a valuable tool for HRV measuring under ideal conditions and shows great potential in becoming a more practical alternative to ECG for HRV tracking and analyzing. Both methods for measuring HRV offer accessible tools for diagnosing how the ANS is functioning, which can further help early detection of certain conditions and provide insights into the overall health of the body.
What is the key difference between HRV and HR? How and when should we track and improve heart rate variability?
Recent developments in digital health have introduced various wearable devices and apps for acquiring vital biomarkers and obtaining advanced health metrics, ultimately transforming the way we measure data and use it to understand and improve our health. A metric that has recently received a lot of attention is called Heart Rate Variability (HRV), and owes its popularity to the ability to provide valuable, non-invasive insights into our health status and expand the potential of digital biofeedback.
Although often measured alongside the Heart Rate (HR), HRV is a metric that offers more detailed and accurate information than HR alone. To understand how these two vital measurements can be fully and unambiguously interpreted, this article will explain the similarities and differences between HR and HRV, as well as how they can be applied to health tracking and improvement.
What is Heart Rate and how to use it
Measuring HR means obtaining an average beat-per-minute (BPM) value, which tells us how fast the heart is beating. Easy to record and interpret, HR has perhaps been the most widely used metric in medicine for centuries. Most people show an average HR value of somewhere between 60 and 100 BPM in a rested state. Different HR readings can offer insights into the state of our cardiovascular system.
A low HR reading shows measures of < 60 BPM and usually indicates that the body is in a rest-and-digest state. Low HR is also normal in athletes or during sleep. It can also be a sign of a condition called “bradycardia”, which causes fatigue, dizziness etc. A higher HR reading shows measures of >100 BPM and usually means that the body is under physical or psychological strain. High HR is normal in some cases, like during exercise, or it can indicate a condition called “tachycardia”, which is associated with various symptoms and complications.
However, the heart rate is, per definition, a measurement that provides an average value and only shows how many times the heart beats in a minute. An average of 60 BPM could mean that the heart beats once every second, or that it alternates at a 0.6 seconds followed by a 1.4 seconds rate, or at any of the endless range of time intervals between successive beats. In summary, the heart does not beat to a regular pattern, but rather slows or fastens its pace to adapt to several physiological or pathological factors. HR measurements at any given time, therefore, provide limited information about human health or well-being.
What is HRV and how to use it
HRV represents the variability in the time intervals between successive heart beats. In contrast to the HR, the HRV takes into account what happens in each heartbeat. Such variability in the heart activity has its origins in the Autonomic Nervous System (ANS), which comprises two branches and regulates various automatic processes in the body, including digestion, heart rate, breathing, even sexual arousal. . Given its strong connection with the activity of the ANS, measuring HRV has a wide range of applicability.
By helping us understand the current state of the autonomic nervous system and how well it is functioning, HRV provides insights into all the processes in the body that are equally controlled by ANS. This means that tracking HRV can help us understand the link between cardiovascular activity and the respiratory system, stress management, fitness and recovery, and other health related processes and functions inside the body.
A high HRV at rest usually indicates that the heart is operating well, and that it adapts to various stressors quickly and efficiently. On the other hand, a low HRV at rest can be an indicator of too much stress, a previous intense workout, or several other impaired processes in the body.
HRV therefore represents a metric that is more insightful, widely applicable, and valuable than simple HR recordings. However, quantifying the variability between successive heartbeats requires the calculation of complex scores from the HRV readings and more sophisticated tools for interpretation than simple HR readings.
Vital biomarkers collecting and interpreting
Recent advancements in technology have enabled smartphone apps and wearable devices to collect and interpret HRV metrics in a non-invasive, affordable, and convenient way. This makes HRV readings within everyone’s reach, easy to interpret and implement in your health management habits. HRV and HR have commonly been associated and are even mistakenly considered equivalents. Understanding the difference between HR and HRV and how they can be used is very important, as it can help you reach health related goals and establish better habits more efficiently.
When to measure HR
The best moment to measure HR at rest is in the morning, ideally in bed, after a good night’s sleep and before the first coffee. HR at rest provides basic insight into how well your heart is functioning, whether you exercised enough etc. Once you know your average HR at rest, it is indicative to track it during strenuous conditions (like during exercise), as it reveals how physical exertion affects your heart rate in real time. This type of tracking is a useful basic tool for training your heart and adjusting your routine to match the state of your cardiovascular system.
When to measure HRV
Interpreting HRV metrics offers insights into the way the ANS is functioning, which can help you understand the state of your overall health, as well as your body’s ability to manage stress and recover from physical exertion. However, that also means that HRV is a very sensitive metric and, therefore, some additional planning and interpretation are required when it comes to its measurement, especially when performed in short intervals.
While valid HR can be measured during an activity, HRV is more easily interpreted before and after a certain task or challenge, in more “controlled” conditions (e.g. without interference). For measuring the effect of meditation on stress recovery, it makes sense to compare HRV before and after that activity in absence of additional stressors or relaxants.
The most important thing to keep in mind is that although HRV and HR are commonly considered to provide similar vital data, they are in fact very different from one another and should be measured individually. HR is a valuable tool for basic medicine and for interpreting the immediate effect of physical and psychological exertion, while HRV offers deeper insights into the functioning of the ANS and all the biological processes it regulates.
If you are interested in knowing more about HRV and uncovering the full potential it has for helping the body learn how to better manage stress, improve fitness, and even help improve mental health, visit our full collection of HRV related articles.
Although the mobile health apps market is snowballing, innovators will need to offer some extraordinary benefits to users. Their expectations also will grow. Our managing director, Matthias Puls, argues that the integration of vital data and biomarkers will be imperative.
The market will be worth 979 billion EUR by 2025
They are undisputedly the stars of the digital health scene right now – apps in the area of preventive healthcare. Especially in Germany, they have received a lot of attention from the public over the past few months. This is primarily due to the new Digital Health Care Act (DVG), which paved the way for digital health applications to be reimbursed by health insurers. Some digital health apps have already successfully completed the certification process and thus been added to the list of services that doctors all over the country can now officially prescribe. They have been met with a highly positive response from patients.
A representative study by Statista from July 2020 revealed that 59 percent of respondents could well imagine using a medically prescribed application. In line with this, a survey of 18 participating health insurances shows that only three months after the start of statutory reimbursement, more than 3,000 digital health apps (DiGA) have already been prescribed by doctors. All of this suggests optimal conditions for providers in a rapidly growing market – and further studies reinforce that there is an immense opportunity. Global consulting company Roland Berger estimated the global revenue potential for digital health applications at 1 trillion EUR by 2026, 59 billion of which will be generated in Germany (by comparison: the European Union will account for 239 billion euros). Insight Partners predicts a worldwide potential of $246.8 billion for mobile health alone by 2025. Let’s briefly recall where we’re coming from: In 2017, revenue in this segment was 18.73 billion EUR worldwide.
Only the apps that offer the most value to the user will win
Will this mean endless market opportunities for existing and new players? Unfortunately, it is not quite as straightforward. More likely, it can be presumed that the market will consolidate to just a few apps over the next two to three years. This assumption is based on the fact that only a few different apps will be prescribed for each medical indication. Therefore, the best – in other words, the most effective – apps that can deliver the most significant value will prevail. Many digital health interventions exist in the form of “app content.” Here a trend toward “the winner takes it all” can be expected, as can already be observed in the meditation apps market. Particularly the applications Calm and Headspace have maintained substantial market share in this field.
The structure of a digital health solution can essentially be broken down into a few main components:
Anamnesis/Onboarding.
Interpretation of anamnesis and (in some cases) complementation of such through additional data recorded within the app.
Interventions in the form of content.
(In few cases) continuous data points recorded within the app in order to individualize programs and review the user’s progress.
The biggest challenge for digital health applications will be to demonstrate that their content provides significant value for users – more value than the competitors’ apps. Solely referring to successfully completed clinical studies will no longer suffice as a unique selling point, neither towards consumers nor towards health insurances. The latter is especially true for the German context, in which certified digital health applications (DiGA) directly enter into price negotiations with the National Association of Statutory Health Insurance Funds (GKV-SV). Arguably, digital health applications can provide the most value if they are able to interpret each user’s unique characteristics and offer individually tailored interventions. However, this requires a sound understanding of relevant vital data and biomarkers; in order to individualize offerings, relevant data points like such must be analyzed on an ongoing basis (see app components 2 and 4 as mentioned above). Many digital health applications are currently exploring technical functionalities to realize this, yet most providers are still in the early stages of implementing respective functionalities. Nevertheless, it can be expected that a general trend towards precision medicine will prevail.
Conclusion: vital data and biomarkers will be necessary to succeed
Digital health providers who want to establish themselves on the market in the medium and long term must offer effective solutions. Effectiveness can be achieved in a particularly transparent manner if relevant vital data and biomarkers are continuously observed. The capture and evaluation of this data help to individualize the solutions and has the great potential to allow patients to accompany the progress of their therapy at any time on the basis of quantitative evidence. From a psychological point of view, science has shown that a better understanding of one’s own status quo and progress helps users stay on track longer. Additionally, continuous generation of quantitative evidence showing the positive effect of digital health applications will also promote the public’s confidence in them in the long term.
So, where does this leave app developers? A major step will be integrating the measurement and analysis of relevant vital data and biomarkers. Cardiovascular vital data, for instance, could provide considerable added value to a range of applications. Remarkably the scientifically proven biomarker heart rate variability (HRV), reflecting the physical stress on the autonomous nervous system, has immense potential. The range of use cases for HRV is very diverse and extends from mental health, pregnancy, and nutrition/obesity to cardiovascular diseases, chronic diseases, and telemedicine platforms.
Moreover, (health insurance companies are likely to be interested in a “vital data building block” for their own and third-party solutions as a quality indicator. Appropriate software development kits (SDKs) are already available on the market, enabling such measurement and analysis functions to be integrated into the developer’s app without the need for additional wearables. Without question, digital preventive healthcare is about to leap to a new, groundbreaking level. This next-level will likely only be reached by solutions that can record and interpret relevant vital data and biomarkers and use them to control their therapeutic success.
Health is wealth and knowledge is power, they say. These days, it seems like everyone is talking about a relatively new and potentially revolutionizing health tracking unit called Heart Rate Variability (HRV). We believe there is a good reason for this, and today we are here to help you understand the benefits of HRV tracking, how it is connected to the nervous system, and how monitoring it can improve stress management and help your body perform at full capacity.
Thanks to its ability to provide insights into how different behaviors affect the nervous system, heart rate variability has the potential of becoming a preventive tool and assist the healthcare system in the effort to reduce the ever-rising numbers of patients suffering from cardiovascular diseases. It is also a valuable tool in understanding how the nervous system influences performance, endurance and adaptability of the body.
At KENKOU, we believe uniting medical knowledge with technological innovation can help people take charge of their own health in an easy, affordable, and sustainable way, so we combined medical and health tech expertise to deliver a product that brings cardiovascular health insights closer to those who need it the most – actual patients.
What is HRV and why is measuring it important?
“HRV represents a non-invasive, pain free, economic and simple measurement.”
Sylvain Laborde, German Sport University Cologne
Short for Heart Rate Variability, HRV is a measuring unit of the variability between heart beats. It represents changes in the time interval between successive heartbeats. A healthy heartbeat is no metronome – it beats at varying intervals, and the distance between these beats can tell you a lot about the state of your nervous system, your body’s adaptability to various situations, its readiness to cope with stress, and how quickly it can recover.
Many people misinterpret the BPM (beats per minute) rate, assuming that a heart rate of 60 BPM means that the heart beats once every second. In reality, the distance between two consecutive heartbeats (also known as the RR interval) might be 0.95 seconds, while the following two might beat with 1.05 seconds between them. HRV tracks the changes in time between successive heart beats to demonstrate how well the nervous system is responding to various factors that affect it.
What affects HRV and why does it matter?
One of the main roles of the nervous system is helping the body handle everyday life challenges in the best way possible. The so-called autonomic nervous system (ANS) regulates many vital functions of our organism, like breathing, sweating, or maintaining the correct body posture. Most of these functions, including heart activity, are regulated without our consciousness.
ANS sends signals to our heart through its two branches – sympathetic and parasympathetic. These two ANS branches are constantly active but in varying intensities, depending on the nature of the situation the body is faced with. When dealing with stress (like performing work on a tight deadline), the sympathetic branch activates stress hormones, putting the body in “fight or flight” mode. In contrast to that, the parasympathetic branch activates during more relaxed and less stressful times, placing the body in “rest and digest” mode.
ANS is constantly working and regulating functions that might appear to be automatic, like breathing, digestion, and, of course, the heart rhythm. As an independent unit, the heart rate on its own beats to a rhythm that is dictated by the sinoatrial (SA) node, which acts as a built-in pacemaker, maintaining the heart rate at around 100 beats per minute. However, the balance between the sympathetic and parasympathetic branches of ANS changes its rhythm throughout the day, either allowing one branch to dominate or by keeping them in balance. The constantly changing configuration of the influence ANS has on the heart rhythm ensures a flexible adaptation of the cardiovascular system to internal and external demands on the body.
What this means is that any one of the two branches of ANS can be dominating at any given time, or they can remain in perfect balance. If the sympathetic branch is dominating (like when we are facing a stressful situation), the heart rate goes up and the heart rhythm becomes uniform, which causes the HRV to go down. On the other hand, if the parasympathetic branch is dominating (like when we are relaxed and comfortable), the heart rate goes down and the beats are more spread apart, causing the HRV to go up. In general, a higher HRV is an index of a well balanced regulation of cardiovascular functioning.
What is a good HRV measurement and how does it affect overall health?
A high HRV is a sign of a well functioning parasympathetic system, which extends the adaptability of cardiovascular responses to various challenges. This is why a high HRV is usually considered to be a good sign. However, as we will see through many examples, a high or low HRV alone does not always indicate optimal performance capacity (or the opposite).
A low HRV rate usually means that the sympathetic branch of the ANS is dominating and the body needs to be ready to take on more stress than normally, making it beat faster and lowering HRV. This is not necessarily bad. For example, when the body is physically exerted (like during an intense workout), the nervous system sends signals to the heart that its focus should be on managing the exertion, rather than focusing on internal processes like digestion or recovery.
The low HRV in this case simply indicates the efficiency of the nervous system to prioritize certain functions inside the body. This explains why observing HRV alone without taking into consideration other factors that could be affecting it is insufficient and can result in inaccurate and misleading conclusions.
The recovery ability of your cardiovascular system is measured through the root mean square of successive differences between normal heartbeats (RMSSD). The higher the variability value, the more capable your heart is to cope with challenges and recover from them. As recovery ability values vary depending on the age, gender and other factors, the following table shows average RMSSD for healthy men and women of different ages.
How is HRV measured and what equipment does it require?
Thanks to advanced technology and widespread use of smartphones, measuring heart rate variability represents an affordable, easily accessible and non-invasive method for monitoring health. However, analyzing and interpreting the collected data is a far more complicated process. When it comes to HRV, each patient has to be observed as an individual with a unique body structure and their own specific way of processing and reacting to factors that affect the nervous system.
This is why, when it comes to result interpretation guidelines, there is no “one size fits all”, which is only one of many reasons HRV data can be difficult to interpret. The good news is that, over time and with experience, it becomes much easier to read and understand the collected data.
What are the benefits of measuring HRV?
Tracking heart rate variability and interpreting its units has the potential of creating a new niche in the health tech industry. It requires no medical hardware or additional healthcare costs and eliminates the need for constant doctor’s supervision, while its convenience and ease of use have the potential of bringing health monitoring closer to patients. In addition to that, understanding how HRV is linked to health affecting habits like smoking and drinking, or sleep quality and diet, can help millions of people take better care of their health and help them develop sustainable and long-term healthy habits.
By enabling patients to measure the scientific biomarker HRV themselves, general awareness around health and the importance of preventative care is raised. Measuring HRV regularly helps people not only understand their nervous systems and how it regulates the heart rhythm, but also teaches them how they can improve overall performance, manage stress better, and live longer and happier lives.
HRV data-interpreting tools therefore have an immense potential in leveraging digital health, as they provide metrics which provide insights about the health of the nervous system, stress reactions, and consequently the entire body. HRV is able to monitor digital therapies (and their effectiveness) over time, which is urgently needed in health tech.
Additionally, measuring HRV is a necessary first step towards improving it. A scientifically proven way to improve HRV are biofeedback exercises. Common HRV biofeedback exercises leverage the physiological connection between the breath and the heart and provide individuals with real-time feedback on their current HRV while performing a breathing exercise.
In conclusion, HRV measuring tools enhance the value of countless health related apps, whether they focus on fitness and performance, pregnancy tracking, heart health or other vital information that can help people understand and improve their overall health.
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