From the Guidelines
Heart rate variability (HRV) is a valuable biomarker for overall health and autonomic nervous system function, with higher HRV generally indicating better cardiovascular health, stress resilience, and recovery capacity, as supported by studies such as 1 and 1.
Key Findings
- Research has linked low HRV to increased risk of cardiovascular disease, diabetes, depression, anxiety, and poor outcomes following heart attacks, with a relative risk in the range of 2 to 3, as reported in 1.
- HRV has been studied as a tool for monitoring athletic training load and recovery, with decreased HRV often signaling overtraining or inadequate recovery.
- Clinical applications include using HRV biofeedback for stress management, anxiety reduction, and improving emotional regulation.
Measurement and Analysis
- The measurement typically involves recording beat-to-beat variations in heart rhythm using ECG, chest straps, or photoplethysmography sensors in wearable devices.
- HRV analysis methods include time-domain measures (RMSSD, SDNN), frequency-domain analysis (examining high and low frequency bands), and non-linear methods, with the power-law relationship being the most extensively studied nonlinear method, as seen in 1.
Practical Applications
- For those interested in monitoring their own HRV, consistent daily measurements (preferably in the morning upon waking) using a reliable device provide the most valuable data, as HRV fluctuates naturally throughout the day and in response to various factors including stress, sleep quality, and physical activity.
- It is essential to consider the limitations and potential biases of HRV measurements, such as the influence of circadian rhythms and patient activity, as discussed in 1.
From the Research
Heart Rate Variability (HRV) Research
- HRV is significantly associated with average heart rate (HR), providing information on both HR and its variability 2
- The association between HRV and HR is both a physiological phenomenon and a mathematical one, determined by the autonomic nervous system activity and the nonlinear relationship between RR interval and HR 2
- Lower HRV is associated with a higher risk of cardiovascular events and mortality, with a pooled hazard ratio (HR) of 2.27 for all-cause death and 1.41 for cardiovascular events 3
- HRV parameters are significant predictors of higher mortality across different ages, sex, continents, populations, and recording lengths, with lower HRV parameter values associated with higher mortality 4
Factors Affecting HRV
- The autonomic nervous system (ANS) plays a key role in regulating HRV, with the sympathetic and parasympathetic nervous systems interplaying to regulate HRV 5
- Various factors affect HRV, including pathological, physiological, psychological, environmental factors, lifestyle factors, and genetic factors 5
- High HRV is associated with healthy conditions, while low HRV is associated with pathological conditions 5
Measurement and Analysis of HRV
- Ultra-short-term (UST) HRV measurements of less than 5-min duration have been investigated for their criterion validity compared with short-term recordings 6
- UST HRV measurements are proxies of proxies, seeking to replace short-term values which estimate long-term metrics, and require compelling evidence to forecast real-world health or performance outcomes 6
- The analysis of HRV is a well-known non-invasive technique to identify the functioning of the autonomic nervous system, with the variation in the time between two heartbeats providing reliable information about the interaction of the sympathetic and parasympathetic nervous systems 5