Smart Watch: How smart is it?

By Yu Kiu Victor Chan

In recent years, major electronics companies such as Apple, Garmin and Fitbit have been competing for the wearable health technology (WHT) market. Despite the COVID-19 pandemic, the global smart watch market grew by 20% in revenue in the first half of 2020 and close to 42 million smart watches were shipped (Global Smartwatch Market Revenue up 20% in H1 2020, 2020). Their products are in the form of smart watches or electric wrist bands, that are advertised to be capable of monitoring health conditions of the user. In the first few iterations of WHT, it offered its users basic functions such as heart rate detection and it was seen as a gimmick to boost sales. However, in recent years, manufacturers claimed to have developed more advanced functions in WHT, such as electrocardiogram (ECG) detection, blood oxygen (O2) detection, sleep tracking, etc. This review aims to introduce the latest advancements in WHT and discuss the limitations and potential directions of its development. 

WHT monitors cardiovascular health by measuring certain health parameters such as ECG and blood O2 levels. Currently, several smart watches — such as Apple Watch, Samsung Galaxy Watch, and Fitbit Sense — are advertised as an FDA-approved ECG monitoring device. Usually in a medical context, an ECG is used to measure the cardiac electrical activity and is able to detect any cardiac abnormalities, such as atrial fibrillation and cardiac arrythmia. Since ECG is usually conducted in a hospital using electrodes connected to the body, it is not conducted frequently for an average person. The smart watches aim to provide a more accessible way for individuals to monitor their own cardiac health. By detecting user’s health parameters, it gives health advice or identify potential risks of cardiac diseases. 419,297 participants were recruited in a study investigating detection of atrial fibrillation by smart watches (Perez et al., 2019). 2161 participants received a notification of irregular pulse within the monitoring period of 117 days. Among those participants who were notified, 84% were found to have atrial fibrillation. It shows that smart watches may be an inexpensive and non-invasive approach for long-term cardiac health surveillance and management.

Apart from detection of non-infectious diseases such as atrial fibrillation, it was recently reported that data collected by smart watches can be used for pre-symptomatic COVID-19 detection (Mishra et al., 2020). From a cohort of 5,300 participants, 32 were infected with COVID-19. Among the COVID-19 cases, 26 (81%) had alterations in heart rate, number of daily steps and time asleep. 22 cases were detected before symptom onset, and four cases were detected at least nine days earlier. On the other hand, with retrospective smart watch data, it was found that 63% of COVID-19 cases could have been detected before symptom onset. This study shows that smart watch data is valuable for early detection of diseases. In the current pandemic situation, early detection is important to control the spread of the virus. Diagnostic methods such as nucleic acid tests are highly accurate, but it is a labour-intensive and time-consuming method, as it involves laboratory testing and professional knowledge. Since WHT are already widely deployed in the consumer market, the basis of smart watch detection is well established. Although it is not as accurate as nucleic tests, it is a low-cost method to screen large numbers of individuals for potential infections. 

However, despite the applications and benefits of WHT, they also have disadvantages that limit their use. First, reliability of the data is a great concern. For example, it has been reported that although the Apple Watch has good validity in heart rate during walking, but as exercise intensity increase, its validity decreases (Khushhal et al., 2017). As WHT by nature are not verified medical-grade devices, they are not expected to deliver medical-grade accuracy and can only serve as a reference for the user. However, it may be misleading for consumers who purchase such products expecting accurate results. It may cause unnecessary panic for the user if false positive results were obtained, or delayed treatment if false negative results were obtained. Second, privacy of the user should be considered. Most of the WHT in the market right now are paired with mobile phone when in use and have cellular or GPS functions. As WHT collect a lot of personal information, it is a reasonable concern of how the data is used and stored. The security of the data is highly dependent on the cybersecurity measures of the companies and consumers have limited control over how the data is managed. The privacy of users would be at risk if the data were mismanaged. 

So, what would be the next breakthrough in WHT? The health monitoring technology in smart watches are becoming more advanced and it is foreseeable that the data will become more reliable with more research and development. With the increasing popularity of WHT, it can become a useful tool for monitoring not only personal health but the overall health of the community. The data would be useful for health policy planning of relevant authorities to improve general well-being of the population. Also, combining such data with genetic counselling services, it can become an all-round personal health monitoring device and give relevant health advice for the user. This would alleviate the burden to the public healthcare system as health monitoring could be conducted 24/7 at home. But it should be noted that privacy and data security should remain the priority, and the data should only be shared with the consent of the user. 


Counterpoint Research. 2020. Global Smartwatch Market Revenue Up 20% In H1 2020. [online] Available at: <; [Accessed 9 December 2020].

Perez, M., Mahaffey, K., Hedlin, H., Rumsfeld, J., Garcia, A., Ferris, T., Balasubramanian, V., Russo, A., Rajmane, A., Cheung, L., Hung, G., Lee, J., Kowey, P., Talati, N., Nag, D., Gummidipundi, S., Beatty, A., Hills, M., Desai, S., Granger, C., Desai, M. and Turakhia, M., 2019. Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation. New England Journal of Medicine, 381(20), pp.1909-1917.

Mishra, T., Wang, M., Metwally, A., Bogu, G., Brooks, A., Bahmani, A., Alavi, A., Celli, A., Higgs, E., Dagan-Rosenfeld, O., Fay, B., Kirkpatrick, S., Kellogg, R., Gibson, M., Wang, T., Hunting, E., Mamic, P., Ganz, A., Rolnik, B., Li, X. and Snyder, M., 2020. Pre-symptomatic detection of COVID-19 from smartwatch data. Nature Biomedical Engineering, 4(12), pp.1208-1220.

Khushhal, A., Nichols, S., Evans, W., Gleadall-Siddall, D., Page, R., O’Doherty, A., Carroll, S., Ingle, L. and Abt, G., 2017. Validity and Reliability of the Apple Watch for Measuring Heart Rate During Exercise. Sports Medicine International Open, 1(06), pp.E206-E211.

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