Wearable technology, or wearables, refers to all smart electronic devices that can be attached to the body as an accessory or article of clothing [1,2].  Despite the origins of wearable technology dating over twenty years [3], it was not until the current decade that technological evolution further enabled the design of higher-functioning smartwatches with more elaborate interfaces. In 2014, several tech giants including Google, Apple, and Samsung unveiled groundbreaking new smartwatches [2]. Many of their latest innovations enhance the growing field of digital health by integrating digital technologies and healthcare to enable better health outcomes [4]. More specifically, smartwatches are incorporating functions that monitor medical conditions as a preventative measure to combat health risks and potentially save lives.

Atrial Fibrillation

One such health risk is atrial fibrillation (AF). AF manifests itself as an irregular, and often rapid, heart rate as a result of uneven and chaotic beating of the atria. During an episode, an afflicted patient may experience heart palpitations, shortness of breath, confusion, and overall weakness. AF can lead to complications including blood clots in the heart, heart failure, and stroke. If left untreated, AF doubles the risk of heart-related death and increases the risk for stroke five-fold; nonetheless, only about 33% of patients consider AF a serious condition [5,6]. Diagnosis of AF relies on the results of a standard electrocardiogram (ECG) during a suspected episode. Thus, it can often be difficult to confirm the diagnosis during the limited time frame of a physician visit. Moreover, a significant portion of patients who do not show any symptoms and only face sporadic episodes are likely to be unaware of their condition unless a physician discovers it by chance or following an AF episode that induces obvious or life-threatening complications [7].

Detecting AF with the Apple Watch

To improve early detection and diagnosis of AF, we need new devices that can conveniently conduct an ECG without the presence of a physician. In comparison to readily available, portable heart rate monitors, new smartwatches have an advantage in internet connectivity that enables easy transfer of locally collected health data to doctors. The Apple Watch Series 4, launched in September 2018, features an on-demand active ECG monitor in addition to the passive heart rate monitor from the older generations [8,9]. The titanium electrode at the Digital Crown of the Watch and the sapphire crystal at the back can read the electrical heart impulses in the wearer’s fingertip and wrist, respectively [10]. To start taking an ECG, the wearer needs only to touch the Digital Crown for 30 seconds. If the electrodes detect an irregular heart rhythm, the ECG app immediately alerts the wearer. Moreover, the Apple Watch automatically stores all ECG readings, waveform classifications, and related data in the Health app on the user’s iPhone. The user can then easily share the data with any doctor and receive pertinent medical advice [11].
In January 2019, about one month after the new Apple Watch’s ECG app and irregular heart rhythm notification went live [12], Johnson & Johnson (J&J) announced a collaboration with Apple. Together, the two companies have planned to launch a multi-year research project in 2019 to assess the effectiveness of the Apple Watch Series 4 and an accompanying patient engagement app developed by J&J in detecting and diagnosing AF to improve cardiovascular outcomes [13,14].

Excitement and Pioneer Studies

The partnership between Apple and J&J is not the first time that Apple has teamed up with medically-focused organizations to participate in consumer-based research on the role of the Apple Watch in health monitoring. In late 2017, Apple launched a joint research study, named the Apple Heart Study, with Stanford Medicine to assess whether an already developed app could accurately detect irregular heart rhythms and notify wearers experiencing AF. Unlike the most current model that has electrodes inserted into the Watch’s Digital Crown, the older model tested in this study read and calculated heart rate and rhythm by emitting LED light from the back sensor and detecting the amount of blood flowing through the wearer’s wrist [15]. The study began in 2017, entered its final phase of data collection in late 2018, and was projected to conclude by January 2019 [16,17]. Because the passive monitoring technology under assessment is still used in Series 4 to assist AF detection, findings from this study will still have significant and relevant implications.
Amidst the excitement, prospective wearers should remain cautious about the watch’s detection accuracy and conclusions. In one study with more than 580 participants, for nearly 10% of all trials conducted, the app was unable to read the heart rhythm recordings conclusively. Nonetheless, at other times, the app reported the correct result whether or not the user had AF, 98% of the time for people previously diagnosed with AF and 99.6% of the time for those without AF [18]. The first peer-reviewed study that used an app installed on the Apple Watch to detect AF found that the algorithm of the app was 97% accurate in identifying AF episodes [19].

Concerns and Skepticism

Although several pioneer studies have demonstrated the app’s high accuracy, some question the usefulness of ECG examinations for asymptomatic patients. While such practice has become a regular feature of annual physicals, the U.S. Preventive Services Task Force released a statement in June 2018 pointing out the poor cost-effectiveness of mass ECG screening to prevent cardiovascular diseases (CVD) in asymptomatic adults at low risk and thus recommended against it. The Task Force also reported that data regarding ECG screening in CVD prevention, even for people with high- or intermediate-risk, are still insufficient to prove the practice’s cost-effectiveness [20]. Two months later, in a separate statement focusing specifically on AF, the Task Force reached a similar conclusion: the existing evidence was inadequate for proper evaluation of the net benefit of ECG screening for AF prevention [21]. Despite skepticism from some medical experts, very few studies have investigated the cost-effectiveness of extensive ECG screening in detail.
Other concerns have been raised about the vast difference between the age distribution of people with AF and that of wearable technology users. In the U.S., while adults younger than 55 make up over 90% of all users of wearables like the Apple Watch [22], the prevalence of AF in this age group is only 0.1%, as compared to 3.8% among those 60 years or older and 9.0% among those 80 years or older [23]. Therefore, most existing Apple Watch users, who are at low risk for AF, would likely receive limited benefits from the watch’s on-demand ECG capabilities.

Looking Towards the Future

Despite current doubts, leading technology firms and pharmaceutical companies remain optimistic about the life-saving potential of the new ECG-equipped Apple Watch. “I believe, if you zoom out into the future, and you look back, and you ask the question, ‘What was Apple’s greatest contribution to mankind?’ it will be about health,” said Apple CEO Tim Cook during an interview on CNBC in January 2019. While much more research is needed, it is clear that wearable technology will continue to gain increasing importance in health care. As exciting partnerships form between innovative technology firms and pharmaceutical companies, collaborations will blend the disciplines of health, technology, and medical informatics.References

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