Wearable Health Trackers and Privacy

25 minute read


I originally wrote this for a past iteration of CS3001: Computing and Society at Georgia Tech. I quite like it, and I think the issues are increasingly relevant, so I decided to put it up here.

In 2014, Time Magazine crowned the Apple Watch as one of its "25 Best Inventions of the Year" (Time, 2014). During the same year, they published an article titled "How Apple is Invading Our Bodies", cautioning against the device as "over-connected" and "too intimate" (Grossman & Vella, 2014). Similar sentiments could be found across publications as well as in social media: Technology companies had found a new, ingenious way to track more information about everyone while making their devices more personal than ever. Yet, despite the pushback, devices like Fitbit and the Apple Watch succeeded and grew into an industry of wearable health trackers, which today has hundreds of millions of users (Starner, 2014).

A wearable health tracker is a device that can be worn during daily activity for monitoring health and wellbeing through physiological signals and activity recognition (Martin, 2000). They differ from medical data acquisition devices because of their ability to process signals using on-board computational power, and they differ from other wearable computers due to their design purpose and use case.

Originally, 20 years ago, such devices were designed with the intent of being used as medical devices (Martin et al., 2000; Lukowicz et al., 2000). Past medical devices were bulky and could not be brought outside the hospital room, or exclusively served the purpose of recording data for future analysis. Instead, new approaches used ECG, blood pressure, heart rate and acceleration to synthesize information about a patient's status, recognizing what activity they were involved in or whether there was any anomaly, in which case it could alert medical professionals. One such device, a wristband called AMON, would become the precursor to many of the modern health monitors performing online analysis for activity recognition (Lukowicz et al., 2000). The AMON wristband performed analysis within the device and utilized a mobile phone link to alert the doctor if there was a large deviation, in which case medical center personnel could communicate with the patient through on-screen text messages on the wristband.

In industry, similar wearable devices were being developed for recreational use by companies like Polar for joggers and sports performance. At the same time academia realized the value of heart-rate sensing in tracking user activity, they began to add heart-rate sensing to their own devices, such as the FitSense FS-1 (Martin et al., 2021). The FitSense FS-1 collected track pace, distance, calories burned and heart rate with a wristwatch connected to a heart strap, the baseline for all modern wearable health trackers. Academia and industry gradually became more intertwined as new devices started to enter the market and needed to be studied.

The growth and development of wearables happened in parallel with concerns over privacy in the field. As early as 1998, researchers were beginning to see elements of wearables that could be problematic, especially if combined with existing trends of workplace surveillance (Strub et al., 1998). Many wearables collected information not just from the user but also from their surroundings and the people around them. The ability to track someone's every action could become very intrusive when abused by employers, insurance providers and other companies.

Such concerns have only grown as new devices have reached increasingly wider audiences. Where early devices from FitSense and Polar were considered a niche, it gained more traction as large companies like Nike and Apple joined the area with the Nike+ iPod sport kit (Erdmier et al., 2016). In 2015, it was reported that one in five American adults already owned a wearable device and that revenues from wearable devices would double in the coming years.

Newer devices are now being used by as many as 388 million users and form a market generating billions of dollars in revenue (Wareable, 2021). Fitbit and Apple Watch have become ubiquitous, providing similar functionality with much greater comfort than past wearable health trackers. They've also started to integrate with smartphone health-tracking apps to give the user an easier view of their information or to combine information in various modalities across different devices.

With the growth of the consumer market, more specialized wearables have also promised to help people with their specific health conditions or needs. For diabetics and people who are suffering from diabetes and obesity, wearable health trackers can assist them in making long-term lifestyle changes that positively impact their health (Randriambelonoro et al., 2017). Through personalized, playful commentary, fitness trackers can encourage users to be more careful about their health and motivate them to exercise more. Wearables have also been considered for assisting with other chronic health conditions such as epilepsy, sleep apnea and myocardial ischemia.

Wearables for menstrual tracking have also started to gain traction, with the feature being adopted in specialized devices as well as more common ones like the Fitbit. Using skin temperature to monitor their menstrual cycle, these can assist people who menstruate in fertility awareness or for planning around other symptoms such as stress responses and cravings related to their menstrual cycle (Maijala et al., 2019). While these technologies have been criticized for a medicalization and biological essentialization of womanhood (Keyes et al., 2020), they've demonstrated potential for a more individualized approach to menstrual health. Conditions such as endometriosis and polycystic ovary syndrome have also remained understudied, remaining a future prospect for newer wearable technologies to be individualized even more for their users.

The most common specialized application for such devices is still as a tool for exercise and wellness. They have been often used for such purposes, both by people with more active lifestyles and those with sedentary ones and the fitness sector has only grown since then. However, it's been observed that wearable health trackers often have a much greater effect on behavioral change in those with sedentary lifestyles (Lidynia et al., 2017). The health trackers can induce those with sedentary lifestyles to get up and walk or do more exercise and eat healthier based on the feedback provided from the wearable to the user.

As such exercise-oriented devices have become more popular, the companies developing them have accumulated a wealth of identifiable personal health information on their users and started to share it with third parties outside their companies, such as advertising companies or insurance providers. Among these, user studies have shown that the most concerning applications from the consumer's point of view is the potential for information to be shared with employers or insurance providers (Velykoivaneneko et al., 2021). The sharing of such information with an insurance provider or employer would give the companies an ability to use that against them, such as by increasing the premiums they have to pay for their health insurance. As such, personal health information is actively regulated but an important problem emerges with wearable health trackers: Most datasets from wearable health trackers are not classified as personal health information.

In the US, personal health information is regulated through the Health Insurance Portability and Accountability Act (HIPAA), a federal law enacted in 1996 to protect sensitive health information from being disclosed without patient's consent. Currently, wearable health trackers aren't devices covered under HIPAA and a survey of wearables in the market found that only one major vendor of wearable devices indicates that its devices are HIPAA-compliant (Kumari et al., 2017). The rest of the vendors did not factor HIPAA into their design considerations, as there is no need for them to consider it under present regulation. In 2009, the HITECH Act was passed to regulate the emerging area of telehealth and electronic health information, but this didn't affect wearables at all either.

At the moment, the only condition that makes HIPAA apply to wearable health trackers is if the data is directly shared with doctors or hospitals. While this was the original purpose of academic wearable health trackers, this is very rarely the case with current devices in the market. However, even if the wearable devices are affected by HIPAA, the present HIPAA laws only offer protection if the data is identifiable, but de-identified data can easily be re-identified when the data collected is as personal as wearable health trackers.

There has been some room for the Federal Trade Commission (FTC) to regulate wearable health trackers, as a result of the sharing of personal data with third parties. The FTC sets guidelines for protecting consumer data and provides privacy protections for the users. Usually, the FTC only takes legal action when companies overclaim what security and privacy protections they provide to users. Thus, it is unlikely to intervene in actively regulating wearable health trackers as long as there isn't misleading information from the companies developing the devices.

The Food and Drug Administration (FDA) also plays a part in the regulation of wearable health trackers. However, the FDA has actively opted against regulating wearable health trackers as medical devices (Erdmier, 2016). Despite medical professionals being involved in the design of these products and their use of various physiological signals, FDA considers almost all wearable health trackers as "low risk general wellness" devices and refrains from including them into its regulatory classification. However, the FDA has left the door open to regulating some wearable health trackers if they become more invasive, similar to implanted devices or shift from monitoring to treatment, such as providing telehealth guidance over an app. Nonetheless, this has left the vast majority of existing devices out of its purview, leaving a regulatory gap when it comes to security practices surrounding the devices themselves. As a result, only a few of the wide range of wearable health trackers are FDA approved, and the rest have very limited regulatory barriers to prevent misuse (Muzny et al., 2019).

Combining HIPAA, FDA and FTC legislations and guidelines paints a picture of the wearable health tracker industry as an area that has the bare minimum of regulatory oversight. None of the institutions has been willing to take an active stance on regulating wearable health trackers and the laws do not apply well to wearable health trackers. Biomedical instrumentation and computing have collided in the area, leaving regulators and legislators unable to handle the dynamic nature of the wearables industry. This has led to personal, trackable information about the users not being provided adequate protections from regulatory agencies. With large gaps in required security and privacy practices, companies' own attention to security problems has also been limited due to a vast majority of the devices being from smaller start-ups or international companies. This systemic flaw has led to a market of very vulnerable wearables, with privacy issues going from hardware to communication.

When it comes to privacy, the first key component is the form factor of the device, as subtle interfaces can track data without informing those around the user but may also protect the user from disclosing what device they are using to those around them. The success of wearable health trackers compared to other head-worn wearables like the Google Glass owes to a familiar, wrist-based form factor and the lack of an invasive sensor like a camera. While wristbands and watches still dominate the market, there have been various other forms in which wearable health trackers have been designed as accessories, playing a key role in the function and subtlety of the system. Some alternatives have featured rings, such as the Oura Ring (Maijala et al., 2019) or earpieces and headphones like the LG Lifeband and Intel Smart Earbuds (Motti & Caine, 2015). Users have expressed comfort over such accessory devices, as it attracts less attention and suspicion from people around them, whereas more obvious wearable health trackers can draw unwanted attention.

Across studies, users have said that aside from cameras and microphones, the sensor that most concerns them is GPS and other location tracking functionalities (Velykoivanenko, 2021). Many users have indicated interest in disabling location tracking if they are able to do so and being concerned over the ability of the companies to track their location if not. Interestingly, this points to a misconception on the users' part, as many wearable health trackers do not contain GPS sensors and use accelerometers to obtain most of their activity recognition data. Meanwhile, most users are unaware of the presence of the accelerometer and how a wearable health tracker actually collects movement information.

Furthermore, activity recognition allows much more complicated information to be inferred from user activity data. For example, it is possible to deduce that a user is Muslim based on them waking up earlier during Ramadan. Similar observations can be made for a multitude of other personal information such as age, gender and sexual orientation. Current user studies have shown a lack of concern to the ability to infer such sensitive information from user activity, but often such effects disproportionately affect vulnerable minorities and people living in countries where religious or sexual minorities are persecuted, which the studies have not been done in.

Some wearable health trackers have started to integrate their technologies with social media apps, gamifying exercise and promoting their devices through user activities. Users have indicated that they are not concerned at all with this type of sharing, as they are fine with sharing all such information with their friends, rather than other third parties such as advertisers (Gabriele & Chiasson, 2020). Among typical metrics used in health tracking apps linked to wearable health trackers, users were most uncomfortable with sharing their weight graph with anyone. Users have also said that they are less willing to share information with the general public than with friends or colleagues. However, users do not take any precautions to apply such beliefs in practice, often leaving the sharing settings at their default. Compounded by public sharing practices in social media apps, this points to another privacy vulnerability, where personal health information can repeatedly be widely broadcasted on social media without intent.

Due to lacking security practices, information from wearable devices during communication can be hacked and collected without a user being aware of anything. Most wearable health trackers use the Bluetooth Low Energy (BLE) wireless communication protocol, a standard for short-range wireless communication (Das et al., 2016). Researchers have found that they can find information such as what fitness tracker a user uses, their exact location and what activity they are doing at a given time from the Bluetooth packets. This information can then easily be used to identify the person who it came from. This is a very concerning flaw as it can easily allow people to get personal health information they should not have access to. For example, an employer can track the activities of their employees using sniffers which collect Bluetooth data from around the office.

While short-range Bluetooth is among the largest flaws, there are several points of vulnerability even after the data is collected. Health apps' local data storage is inconsistent, and can sometimes be accessed by third-party apps due to file management permissions on phones (Muzny et al., 2020). Often, data from the health app is then uploaded to the cloud or another internet-based storage. Since the data from these devices is not considered personal health information, there are limited protections once these are in the servers. Access practices, encryption and server security have very high variance across companies, and sometimes the information is stored on third-party servers. At each of these stages, there are ways for data from wearable health trackers to be obtained by people or organizations who weren't supposed to have access to it.

The current direction of wearable technologies and its interactions with other industries point to more concerning trends, even for parties who the wearable provider intentionally granted access to. Insurance providers are increasingly interested in the data, going as far as to incentivize the use of these devices by offering discounts to those who track their activity (Bender et al., 2017). This creates new room for discrimination based on health conditions or behavioral information the insurance providers can obtain from the data.

Wearable health trackers are becoming smaller and less noticeable with developments in miniaturized electronics. They are also spreading very fast, as more and more users find an appeal in tracking their activity to improve their health. This will only cause existing problems with wearable health trackers to become more prominent, and further demonstrates the necessity of the industry to be regulated.

The larger companies in the wearables industry such as Apple and Huawei are also growing much faster than others, which will further the standardization of information from wearables, which may cause a single vulnerability to have much larger impact. As the giant technology companies at the forefront of this industry grow more, there exists an increasing potential for market capture, in which the companies may freely look for opportunities to extract more from their customers (Zuboff, 2015). This can be through visible practices such as subscription policies to maintain data access or through invisible sharing practices such as selling user data to other companies. Through these future trends, surveillance capitalism and the scale of tech corporations may compound the risks posed by wearable health trackers.

Existing issues with wearable health trackers and their even more concerning future trends necessitate a response from every party involved with the development, use and regulation of these technologies. For two decades, wearables researchers have mentioned the need for more regulation of wearables used for health, but current legislation still hasn't considered wearable health trackers as an important issue (Martin et al., 2000). Personal health information legislation should be updated to consider information from wearable devices as well as other risk factors such as the ease of re-identifying anonymized data. The FDA needs to start regulating wearable health trackers, either as medical devices or as a new category.

User awareness of problems in wearables also needs to be improved, through community groups, user interactions and journalism. Research and user studies have repeatedly demonstrated a misunderstanding of threats posed by wearable health trackers (Raij et al., 2011). Users often get more worried about threats that are mentioned publicly, such as microphones and cameras embedded in devices and not enough concern for problems actually affecting wearable technologies such as behavioral recognition and sharing practices (Motti & Caine, 2015). Community groups should focus on identifying wearables with problematic security and sharing practices, and news about wearables need to be redirected to pay attention to issues such as inferred behaviors.

Industry and wearables manufacturers should adopt more responsible security practices, to protect their customers and themselves from vulnerabilities to third parties. Personal health information is valuable to everyone, so it must be protected with care by limiting and regulating access to servers and file storage containing such information. New design guidelines should be adopted to make sure that wearable health trackers are fitting for the purpose they are being used for, and user data sharing is readjusted for privacy and the interests of users (Alqhatani, 2020).

Researchers working on wearables must display more awareness over the impact of devices and user studies they perform. While attempting to solve a single medical problem, it's easy to create a new tool for surveillance capitalism. Ethical reviews may protect the participants of a single user study, but the position of a wearable device in the larger ecosystem of technology must be noted when creating new interfaces, algorithms or guidelines.

I've discussed the history and evolution of wearable health trackers over the last 20 years, its massive growth with the development of popular devices, and the limitations of legislation affecting it. As a new industry, various issues in security and privacy have been created, caused by a multitude of factors from communication protocols to data sharing practices. Finally, I've mentioned policies that could be adopted by all parties involved with the wearables industry to limit the potential risks.

These factors point to a wearables industry that promises to greatly raise standards in personalized healthcare yet is dangerously integrated with surveillance capitalism. To realize the goals that have been proposed without compromising users, academia and industry alike must pay attention to the long-term impacts of wearable technology. Until the current direction is corrected, the flaws of wearable health trackers will continue to jeopardize their future.


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