Metrics
Low Data Risk
Data risk determines the level at which data can be threatening or damaging to the user27,28. Wearables, in particular, provide detailed health information such as sleep quality29, physical activity30, blood glucose levels31 as well as information about an individual’s surroundings32,33. This category of data is often deemed the most confidential of all personal data13 and can be characterized as highly sensitive. Improper management of wearables data could inflict tremendous harm to the user. Previous studies justify privacy risks by determining the privacy calculus of wearables–that is, whether the risk in privacy is in proportion to the benefit obtained25,34–37. Improper management of such data could inflict tremendous harm to the user. As such, risk can be determined by understanding two distinct categories of data.
Data risk can be reliably characterized by primary data (data collected directly by the wearable device). Wearables that map more sensitive data such as sleep quality, physical activity, blood glucose levels at frequent intervals. This category of data is often deemed the most confidential of all personal data and is a relatively straightforward measure to quantify the data risk incurred from using that wearable device.
On the other hand, the data risk posed by secondary data (data that can be inferred or predicted from primary data) is less apparent and more difficult to quantify. As prediction methods mature, highly sensitive information can increasingly be inferred from less sensitive information38. This concern is the chief reason why data can never truly be anonymized39,40. Ideally, vendors and manufacturers should collect any data that could be utilized to predict highly sensitive information. However, the benefit of most health-monitoring wearables stems from being able to track personal health information, which serves as a proxy for more sensitive information. As a result, while a distinction between wearables that collect moderately sensitive versus not sensitive information is made, most modern-day wearables have the potential to track or predict highly sensitive information.
A list of data types, potential harm to the user, and links to relevant studies are provided in the table below.
| Data type | Potential harm | Citation |
|---|---|---|
| Body temperature | Period cycle tracking, pregnancy tracking | 38 |
| Heart rate | COVID-19 | 41 |
| Location data | Domestic abuse, stalking | 42,43 |
| Location data | Workplace harassment | 44,45 |
Recommended Performance
Vendor does not collect any data that is potentially harmful. Harmful data is categorized as any information that falls under the following categories:
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Physiological data
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Health status data
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Sleep data
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Health risk assessment data
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Predictive health insights data
Performance Explanation
The following are data categories and examples of data that may be collected from wearable devices. This list is by no means exhaustive and should serve as a guideline of what data wearables may collect.
Primary:
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Physical activity data: Steps count, distance covered, floors climbed, type of physical activity (walking, running, swimming, biking, etc), calories burned, pace, speed, cadence, elevation gain, activity duration, move minutes, MET minutes
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Physiological data: Heart rate, heart rate variability, blood pressure, blood oxygen levels, respiratory rate, skin temperature, electro-dermal activity, galvanic skin response, pulse wave velocity, oxygen uptake, minute ventilation
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Sleep data: Total sleep time, sleep stages, sleep interruptions, sleep quality, sleep efficiency, snoring data, bedtime, wake-up time, sleep latency, sleep movement, sleep events (apneas, hypopneas)
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Health status data: Menstrual cycle tracking, glucose levels, blood coagulation levels, hydration levels, sweat analysis, body temperature, basal metabolic rate, body mass index, body composition, lung function, cholesterol levels
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Environmental exposure: UV exposure, noise levels, air quality, allergen exposure, ambient temperature, humidity, light exposure, pollution exposure
Secondary:
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Health risk assessment: Likelihood of health issues (cardiovascular disease, sleep apnea, diabetes, hypertension, chronic stress, metabolic syndrome, COPD, risk of falling in elderly, stroke risk, atrial fibrillation risk, cancer risk)
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Physical fitness level: Estimated VO2 max, fitness age, recovery time, body composition, lactate threshold, functional threshold power, muscle load, training load, training effect, training status, anaerobic training effect, power-to-weight ratio
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Lifestyle habits: Sleep habits, physical activity habits, sedentary time, screen time, dietary habits, hydration habits, stress management habits, medication adherence, smoking habits, alcohol consumption
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Behavioral patterns: Regularity and consistency of physical activity, sleep patterns, circadian rhythm, changes in heart rate variability, social interaction patterns, occupational activity patterns, travel patterns, shopping habits
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Predictive health insights: Predicted onset of conditions like the flu or a cold, risk of burnout, risk of depression, risk of anxiety, risk of heat stroke, cognitive performance, cognitive decline, fatigue prediction, mood prediction, seizure prediction
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Demographic data (weight, height, etc – find some study that cites this)
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Voluntary health data (what medicine is being taken? etc)
Despite most wearable devices not being covered under HIPAA and GDPR only being applied in Europe, they provide the crucial foundational frameworks to determine what kind of data may introduce health privacy risks16,46. Of the categories and examples listed above, the following data categories could cause a privacy risk based on data sensitivity:
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Physiological data
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Health status data
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Sleep data
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Health risk assessment
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Predictive health insights
Other categories may present health data violations depending on the user and what their understanding of consent is, but based on the HIPAA and GDPR frameworks, these data categories present the largest risks to most users. Any wearables that collect data that fall under these categories can pose a problem.
Physiological data such as heart rate and blood pressure, along with health status data like glucose levels, can reveal underlying health conditions that, if mishandled, might lead to discrimination in areas such as employment or insurance47,48. Sleep data provides insights into personal lifestyle and potential sleep disorders, compromising privacy and potentially leading to psychological distress49. Health risk assessments, drawing on primary data to evaluate the likelihood of health problems, may result in unjust discrimination or unwarranted anxiety, especially if used improperly in contexts like insurance risk modeling50. Predictive health insights, which involve analyzing various data to forecast future health conditions, carry similar risks and can also lead to higher premiums or denial of coverage based on predicted health risks. In total, these categories highlight the potential misuse of sensitive health information, potentially leading to tangible harms such as discrimination, social stigma, psychological distress, and financial loss.
Summary
Privacy Metrics
Summary
The need for privacy protections is on the rise, driven by increased susceptibility to privacy invasions and loss of control over private information. Privacy has evolved over time to match the growing needs of society–despite numerous attempts to define privacy1–6, the inherent ambiguity of the concept remains a challenge. However, the ambiguity of privacy should not hinder efforts to study its manifestations and to establish regulations to protect it. A general consensus for more privacy regulation is apparent, and maintaining privacy with other fundamental values like autonomy and liberty is critical7.
Wearables pose a unique privacy threat as adoption increases rapidly across consumer, medical, and research sectors. Wearables have been described as ubiquitous by multiple studies8,9. About 30% of adults in the United States use wearables10. However, this surge in popularity has also brought new privacy considerations11,12. Privacy is especially critical for wearables, as they are increasingly used to measure and record health information (categorized as “most confidential”)13,14. Unfortunately, regulatory bodies like the U.S. Food and Drug Administration do not regulate these devices15 and few legal protections exist to safeguard the privacy of wearables users. Comprehensive health-specific legal frameworks such as the Health Insurance Portability and Accountability Act of 199616 are not applicable to wearables, engendering a significant lapse in health data protection17.
A privacy criterion for health-monitoring wearables is critical. Top scholars and research efforts on wearables privacy have identified the impact of numerous wearables privacy issues. The current landscape for wearable devices is mired by problems such as the consentless exchange of highly sensitive information18,19, real-time collection of data from users20, legal challenges12,17,21–23, perceived privacy concerns by users24,25, and lax security practices and software/hardware vulnerabilities12,26.
De-identification
Public datasets have become exceedingly common, as there are major benefits to higher volumes of data being made available. However, this typically comes at the cost of privacy, and organizations have opted to de-identify data to combat these risks. De-identification strips privacy-sensitive information from the dataset while maintaining other information66. Many opt to de-identify data at time of collection, as it reduces the risk of exposing potentially sensitive data of individuals. De-identification of data is a worthwhile endeavor, as it limits the sensitivity of data being collected–and subsequently, places higher protections of the privacy of users.
It is important to note that re-identification of anonymized data is becoming a serious limiter to de-identification as a method of preventing privacy threats. A report in 2016 found a 320% increase in hacking attacks on healthcare providers75, and the volume and quality of wearable data exacerbated the negative impact of possible hacking efforts by malicious actors. Current methods of de-identification such as K-anonymity55,76, L-diversity69,77, and T-closeness69,76 each present unique challenges when combating re-identification techniques.
Recommended Performance
Vendor de-identifies data.
Performance Explanation
By nature of the request, it would be impossible to determine what de-identification method is utilized by vendors.
Any data that can be tied to health data should be de-identified before sharing.
Data Sharing with Third Parties
Most wearable manufacturers include clauses about sharing data with third-party vendors, who in turn may use the data for purposes outside the extent of the explicit consent provided by users. Numerous service policies of wearables evaluated in this review include general third-party data-sharing provisions, including major vendors such as Apple and Google’s Fitbit78–80. Additionally, few vendors discuss which and why third-party services gain access to users’ personal data; broad, all-encapsulating language is common to account for probable actions (e.g. sharing of data to additional, undisclosed third parties) or possible actions without the need for amendment (e.g. acquisition of data by a merger)81. Furthermore, many include the language of sharing identifiable information if required by law, which could result in harmful legal repercussions to the user. Tech policy researchers in the United States warn on the repercussions of period-tracking apps invading individual privacy due to Roe v. Wade being overturned82–85. As such, sharing data with third parties could be detrimental to a user’s privacy.
Recommended Performance
Vendor does not share data with third parties.
Performance Explanation
None.
Transparency in third-party sharing
Vendors should seek to inform users of any and all data that is shared, along with intent.86 claims that it is becoming increasingly harder to identify and regulate third parties as they are largely not beholden nor obligated to respect the initial privacy agreement between a user and the vendor. The paper suggests a solution where particular types of information should remain confidential, regardless of who may acquire the data. Unfortunately, this requires users and regulators to know which third parties are provided access–supporting the full transparency and disclosures of all third parties provided with user data. A vendor who does not choose to share data with a third party would automatically receive full marks.
Recommended Performance
Vendor discloses all third parties that receive user data.
Performance Explanation
Any language of data sharing with vague or unspecified third parties is not transparent. In one study, human annotators determined the top 5 vague words in privacy policies to be “may”, “personal information”, “information”, “other”, and “some”87. Another study analyzed mobile health and fitness apps to find that privacy policies were frequently not applied to third party links and services88. One researcher goes as far to coin the term “Incognito Problem” to refer to users being provided little to no information on which third parties obtain user data89.
If vendor does not share data with third parties, vendor is awarded this metric automatically.
HIPAA Compliance
The Health Insurance Portability and Accountability Act (HIPAA) is a United States federal law passed in 1996 to protect the health information of patients16. While initially met with criticism, HIPAA has proved capable in practice because of its comprehensive and detailed nature51. With the addition of the 2009 Health Information Technology for Economic and Clinical Health Act amendment to account for electronic health records, HIPAA is an effective and comprehensive legal framework to regulate privacy concerns52. The rise in the popularity of wearables has caused critics to call for further addenda to the existing framework, including a broader range of data types and an update of provisions53,54.
Wearables data should be covered under HIPAA. Under HIPAA, 18 critical identifiers (information specific to an individual that may identify that individual) should be suppressed to maintain the anonymity of de-identified data. The dissemination of data to the public is becoming increasingly common for research or general information purposes55, especially with the unbridled adoption of technology to combat issues in health56–58. Massive, anonymized public health datasets such as NHANES59 are made available by major institutions and collective efforts by scientists. In its infancy, masking HIPAA identifiers proved sufficient in protecting health information52 and should serve as a benchmark for wearables data as well.
HIPAA states that all identifiers must be removed from a dataset and the HIPAA’s Privacy Rule requires patient consent before revealing identifiable health information16. Similarly, wearables should limit the number of HIPAA identifiers collected from individuals. These identifiers serve as one of the simplest ways to associate health information with an individual. And while vendors may argue that any data released will be stripped of any identifying information (including HIPAA identifiers), privacy protections are best afforded when wearables refuse to collect such identifying information in the first place. However, the conclusions made by this metric serve only as a baseline. Numerous peer-reviewed studies reveal that anonymized health data can be re-identified60–63, primarily through the pairing of data from other public sources64–66. Efforts to de-anonymizing datasets are prevalent–the Netflix prize dataset67, AOL web search queries68, and Group Insurance Company anonymized medical dataset (spawning the k-anonymity model to protect privacy)69–71 are three of numerous successfully re-identified datasets previously thought anonymous, leading to speculations as to whether any publicized data can reliability be considered private52. Wearables data is also subject to these vulnerabilities and may pose an even greater risk due to the volume and detail of the data collected. Researchers have raised similar concerns with wearables data65,72–74. Still, limiting access to identifying information bodes well for privacy initiatives.
Recommended Performance
No HIPAA identifiers.
Performance Explanation
Any data that falls under what is outlined as a HIPAA identifier would make a device non-HIPAA compliant. While most wearable devices are not covered under HIPAA, this law provides a comprehensive legal framework to determine what may be important identifying data that wearable devices should collect with explicit consent.
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Name
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Address
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All elements of dates related to an individual
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Telephone numbers
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Fax number
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Email address
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Social security number
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Medical record number
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Health plan beneficiary number
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Account number
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Certificate or license number
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Vehicle identifiers and serial numbers
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Device identifiers and serial numbers
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Web URL
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Internet protocol address
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Finger or voice print
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Photographic image
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Any other characteristic that could uniquely identify the individual.