Did you receive a smart wearable device this past holiday season?

Investigators at The Texas Heart Institute believe smart devices may offer yet another way to track and improve physical and mental health. The Institute’s Medical Director, Emerson Perin, MD, PhD, and researchers in the Center for Preclinical Surgical & Interventional Research recently published a review in the International Journal of Environmental Research and Public Health discussing how wearable devices can be used to monitor heart rate variability (HRV) as a possible new tool to improve personal health.

Smart wearable devices, like smartwatches or rings, can aid in daily health monitoring. Notably, these devices can provide long-term monitoring data for different groups of people under different conditions, such as during exercise, sleep, or rest, and in good health or with disease.

Heart rate variability measures the difference in the amount of time between each heartbeat. HRV is a reliable gauge of a person’s autonomic nervous system function, which helps control heart rate and blood pressure. Two main divisions of the autonomic nervous system are the sympathetic and parasympathetic nervous systems. The sympathetic nervous system increases the heart rate and blood pressure to prepare the body for challenges; the parasympathetic nervous system decreases the heart rate and blood pressure to relax the body after the challenge has passed. A person’s HRV value provides insight into the balance between these two nervous system components: high HRV reflects good adaptation to internal and external factors, whereas low HRV may indicate a reduced ability for the body to adapt to challenges.

Importantly, HRV measurement can provide information about the person’s health status. Studies have proposed that HRV is linked to stress, cardiovascular disease, diabetes, and inflammation. Age, sex, fitness, circadian rhythms, smoking, or medication use can also affect HRV.

Dr. Perin and his co-authors were particularly interested in the ability of wearable devices to perform long-term HRV monitoring to help improve personal health. The investigators carefully surveyed the existing medical literature to learn more about HRV measurement through smart wearable devices.

Many major brands of wearable devices offer HRV monitoring, either on-demand or as a background measurement. Devices that use the heart’s electrical activity to measure HRV (electrocardiogram or ECG) can provide continuous, long-time HRV tracking (like the AIO Smart Sleeve, Firstbeat Sport Sensor, Polar H10 Strip, and Zephyr Bioharness). Devices that use a light source/detector combination on the skin to measure HRV (photoplethysmography or PPG) can be used accurately for continuous monitoring only during sleep because motion can make the readings less precise (including the Apple Watch, Fitbit Watch/Band, Garmin Watch, Oura Ring, and Whoop Band). Third-party apps can use the raw HRV data to provide a more detailed analysis and aid in biofeedback training to help users regulate their heart and breathing rates.

Studies have shown that HRV measurements taken by wearables can provide reliable readings compared to medical-level measurements and suggest that the large datasets from these popular devices could help health researchers answer questions about HRV in healthy and diseased states. Wearable HRV monitoring and specialized apps have been used to monitor and address stress, post-traumatic stress syndrome, and migraine headaches. Low HRV is associated with an increased risk of cardiovascular disease and significantly correlated with heart failure; large-scale HRV research enabled by wearables might help improve risk stratification for heart and vascular disease. Patients with diabetes often have low HRV, with decreased HRV serving as a predictor of negative cardiovascular outcomes in those patients. Pilot studies also suggest that HRV can monitor hypoglycemia (low blood sugar). Additionally, research has shown that HRV measurements could be used to detect inflammation responses, including those in patients with COVID-19.

Dr. Perin and his co-authors point out numerous advantages of using wearable devices to track HRV, including the opportunities for individuals to track their health status long-term throughout their daily activities, for health researchers to perform large-scale studies, leveraging larger sample sizes to address previously challenging issues; for subjects to participate in clinical trials more easily through automatic data collection; and for people to improve their HRV through guided training and feedback.

The authors advocate for greater standardization and consistency in methodology among the various wearable brands, especially the usefulness of 24-hour continuous monitoring. They also suggest that current technology is best suited for short-duration studies (i.e., 1-2 weeks of tracking), and long-term trials will be more feasible as the technology matures.

Dr. Perin commented on the potential value of using this method, sharing, “Since this measurement has been built into so many wearable devices, it should be feasible to design clinical trials to track HRV and monitor individual health. The long-term goal is to develop HRV to improve patients’ mental and physical health.”

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Read Report

Ke Li, Cristiano Cardoso, Angel Moctezuma-Ramirez, Abdelmotagaly Elgalad, and Emerson Perin. Heart Rate Variability Measurement through a Smart Wearable Device: Another Breakthrough for Personal Health Monitoring?  Int J Environ Res Public Health. 2023, 20, 7146. https://doi.org/10.3390/ijerph20247146

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