The Definitions of Health Apps and Medical Apps From the Perspective of Public Health and Law: Qualitative Analysis of an Interdisciplinary Literature Overview

Introduction

Background

The way people monitor their health has changed rapidly in the last decades owing to the smartphone and its widespread accessibility [1,2]. According to the World Health Organization (WHO), mobile health (mHealth) is a general term that covers public health and medical practice through the use of smartphones, sensors, personal digital assistants, wireless monitoring devices, or other wireless devices [3]. It can enable and improve the delivery of health care [4,5]. Mobile apps are defined as software programs that run on smartphones or tablet platforms [6]. Such apps can promote health and primary disease prevention [7,8]. At the same time, apps can support people with chronic illnesses in managing their medical conditions [8,9] or improve treatment adherence [10]. Furthermore, apps offer the opportunity to increase the autonomy of patients without necessarily needing to include physicians [11]. Not only may apps help in improving or monitoring one’s health, but they can also play an important role in health economics as they can help in saving costs and increasing utility for health care systems [4,12-14].

The use of apps in health can have downsides. First, it is unclear whether and how mHealth contributes to a health care system with improved cost-effectiveness. Second, the evidence of a positive health impact through apps is not always available. Some studies suggest a lack of (long-term) evidence for health apps, which indicates a potential risk to the health of mHealth users [7,9,15]. These potential risks may cause unintended consequences for users, their social environment, and the overall health care system [16]. Although some studies have reported positive long-term effects on users’ health [7-11,15], a clear directive on whether apps are an effective tool for diagnosing and treating health issues is yet to be established. Hence, there is a need to disentangle some of the conceptual unclarities in this domain and further advance research.

The potential of apps on the one hand and their risks on the other have drawn the attention of legislators as well. Several countries have started to regulate mobile apps in their function as medical devices—in 2021, the European Union (EU) Medical Device Regulation (MDR) started to uniformly regulate apps as medical devices in Europe [17]. The MDR is not an app-specific regulation as it addresses medical devices in general, including apps and other medical devices (eg, cardiac pacemakers, catheters, and filtering facepiece 2 masks). Apps can be affected by the areas of, for example, data protection, data security, consumer protection, medicine, and social law. App-specific laws, on the contrary, are rare [18,19]. In Germany, apps as medical devices have been officially made available for prescription since October 2020. This was introduced in the Digital Healthcare Act. The Digital Healthcare Act explicitly considers apps as digital health applications (DiGA), which, therefore, fall under app-specific law [20]. Despite all this, regulation—regardless of being app-specific or not—shares no common understanding of apps in the field of health. Although the law is highly dependent on accurate definitions, there is no legal definition of apps in the field of health. On the basis of a standard definition of apps in health, we argue that app developers will be nudged to use evidence-based approaches to develop apps in health. This ensures user safety and reduces the risk of harm [21].

The number of different stakeholders is mainly what causes the current unsatisfying situation. The diversity of stakeholders shows that apps in this field are not geared exclusively toward health care providers but also toward the general public and policy makers. When developing a new app, developers of mHealth apps need to consider patients, clinicians, families, researchers, politicians, providers, and payers alike [22]. Especially in health care systems with public funding, payers and users do not necessarily have to be the same person. In some countries (eg, Germany), health insurance companies have started to reimburse their clients for specific mHealth apps once prescribed by a physician [23].

Objectives

To better understand apps in health and aim at a more precise regulation of such technologies, exact definitions of these terms are needed. The goal of our literature review was to explore existing definitions of health and medical apps in the academic literature, specifically from a public health and law perspective. In this study, we focused on the differences and similarities in definitions and how health and medical apps relate to each other. We summarized the findings, resulting in more holistic definitions of health and medical apps generatively. Furthermore, we presented the differences between the definitions and terms used in research and legal regulation in the United States, the EU, and Germany. To date, existing frameworks have only focused on, for example, user groups [24-26] or technical functions [27-29]. Our aim was to follow a holistic approach that combines the user group, functions, and health aim of the apps. This approach provided us with a starting point that may also support researchers in building a more in-depth understanding of what constitutes health and medical apps. Consequently, we hope that this will help progress the discourse on regulating such apps and provide a basis for further research in this domain.

Methods

To address our study’s objective, we first conducted a backward and forward snowball search of the literature published in 6 different databases. Second, we analyzed the literature by inductively applying a thematic content analysis approach [30].

Inclusion Criteria and Search Strategy

We applied an inclusive, multistep approach to chart interdisciplinary research on health and medical apps. Owing to this paper’s interdisciplinary nature, we searched for publications in the following academic databases that cover scientific literature from various disciplines: MEDLINE (PubMed), The Cochrane Library, Web of Science, Beck-Online, Juris, and Google Scholar. Through this approach, we were able to cover different disciplines (eg, psychology, human-computer interaction, epidemiology, ethics, public health, law, and health economics) that are involved in the field of mHealth. We included and excluded papers based on the criteria described in Textbox 1.

We formed an initial search strategy that we applied to all the databases. Our basic search syntax included terms and their synonyms, such as “health application,” “medical application,” and “definition” (Textbox 2).

We did not conduct a systematic literature review but rather a backward and forward snowball search to better connect different research fields and their understanding of health and medical apps (see the flowchart in Figure 1). The initial database search was conducted on January 21, 2021, and produced 60 papers that provided a definition of health apps or medical apps. All of these papers (60/60, 100%) were used to conduct the snowball search (see the following section for further explanation). Of these initially identified 60 publications, 20 (33%) provided an original definition and, thus, were included (n=6, 30% were identified through the database search and n=14, 70% were identified through snowballing).

Owing to the rapidly developing field of health and medical apps and the corresponding literature being published, we reran the search for updates on February 3, 2022. We identified 144 more publications that offered a definition of health and medical apps during a database search. However, only 2.8% (4/144) provided an original definition, and no other publications were identified during the snowball search. This resulted in a total of 24 publications that were included in our qualitative analysis. Of these 24 publications, 22 (92%) provided an original definition of health apps and 11 (46%) defined medical apps.

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Snowball Method: Backward Search

We formed a citation network using the snowball method after identifying the first set of potential publications from the narrative database search. The snowball search method allows for linking various scientific fields. This is essential as they all have different search terms, leading to overseen but relevant papers in systematic literature searches with a specific search string [31-33]. Our approach followed the guidelines for snowballing in systematic literature studies by Wohlin [32]. The already identified papers (identified through keyword search) served as seed articles (level 1). We screened the reference lists of these seed articles to identify other relevant publications (level 1). As a next step, relevant papers identified through the reference lists of level 1 publications were included (level 2). We stopped after level 2 screening as publications became less relevant to the seed publication the further we continued the search.

Snowball Method: Forward Search

To avoid the bias of citing only older literature (based on the literature search solely through reference lists), we used the platform Connected Papers [34]. This website connects databases from different fields to form holistic citation trees around a chosen paper. This way, Connected Papers allows for forward snowballing (ie, which other reports cited the selected article?) and backward snowballing (ie, which references did the chosen paper use?). Connected Papers displays all papers that cite the publication (level 1) and that cite level 1 publications (level 2) in a tree-like graphic. The multilevel multidisciplinary tree of connected references helped us identify our topic’s core papers. We screened the publications shown in the tree and included them if they met our inclusion criteria.

Qualitative Analysis

One author collected all definitions in a table in preparation for the data synthesis. In total, 2 German authors independently translated German definitions into English following the translation by Kramer [35] that Gesundheits-Apps in German are health apps and Medizin-Apps in German are medical apps. A third author translated them from English back to German to check if the meaning was the same. Disagreements between the authors were resolved in a group discussion between all authors, where a final consensus was reached.

After collecting and translating the definitions from the retrieved literature, we conducted qualitative data analysis for evidence synthesis. Qualitative methods helped us better understand the rationale, perspectives, assumptions, statements, and approaches that researchers used to define health or medical apps [36]. In synthesizing the search results, we opted for an inductive bottom-up approach (conventional content analysis [37]). We developed categories for the qualitative content assessment from the material we screened. This was an iterative process, with new categories being added whenever indicated by the search results. We applied a thematic content analysis approach to the original and translated definitions to categorize the recurrent or common topics [30]. One author coded the definition themes using the software MAXQDA 2020 (VERBI GmbH).

Results

Overview

The basis for the qualitative content analysis was formed by a review of the legal landscape from the United States, the EU, and the particular case of Germany. The given nature of law is to form precise definitions in which every word has a concrete meaning. Although legal definitions need to be exact enough to be used, they also need to be abstract enough to suit individual cases—such as medical apps. We applied the legal definitions of medical apps as mobile medical devices as an understanding lens to later analyze our scientific findings.

Legal Definitions of Medical Apps as Medical Devices

Overview

Apps are not entirely unregulated, but app-specific law is still rare [18,19]. For example, data protection law requires a legal basis for the data processing of an app [38], and the MDR sets high standards of quality and safety for software entering the market as a medical device [39]. Nevertheless, these laws do not use the term app and are not intended to regulate apps only. These laws use broader terms such as data processing or medical device, thus fitting more product categories than just apps. Consequently, apps can be affected by all these laws. Only the German regulation of DiGA and digital care applications (DiPA) is app-specific in the health context. The following sections provide an overview of the legal definitions of medical devices, mobile medical apps, DiGA, and DiPA and their thematic overlap.

Medical Devices

Both the United States and the EU regulate some apps through the control and supervision of medical devices. Although in the United States only the Food and Drug Administration (FDA) is responsible for regulating and approving, in the EU, several national conformity assessment bodies evaluate whether medical devices meet the standards of the EU MDR [40]. Although they are 2 different legal frameworks, the US and EU definitions of medical devices resemble each other—they concentrate on particular intended purposes. Related to the Federal Food, Drug, and Cosmetic (FD&C) Act, the US medical device is “an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including a component, part, or accessory, which is: [...] intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals [...]” [41].

Similarly, the European MDR depicts medical devices as “any instrument, apparatus, appliance, software, implant, reagent, material or other article intended by the manufacturer to be used, alone or in combination, for human beings for one or more of the following specific medical purposes [...]” [17].

Comparing these laws, the definition of medical devices focuses on their intended use for medical purposes.

Mobile Medical Apps

The United States and European countries have recognized various apps and their potential benefits and risks to public health. Consequently, they have published orientation guides and policies defining which apps are considered medical devices, creating the term mobile medical apps. According to the definition of the FDA, a mobile medical app is “a mobile app that incorporates device software functionality that meets the definition of device in section 201(h) of the FD&C Act 11; and either is intended to be used as an accessory to a regulated medical device; or to transform a mobile platform into a regulated medical device” [42].

This definition suggests that a mobile medical app is inevitably a medical device from a legal perspective and, thus, is intended to be used for the same medicinal purposes as a medical device. In parallel, the German Federal Institute for Drugs and Medical Devices orientation guide on medical apps also qualifies medical apps as medical devices, referring to particular intended purposes [43]:

Stand alone software like smartphone apps can indeed be classified as a medical device. In order for this to be the case, the software must be intended by the manufacturer to be used for humans and for at least one of the following purposes pursuant to Section 3 number 1 [Act on Medical Devices] MPG:

• diagnosis, prevention, monitoring, treatment or alleviation of disease,
• diagnosis, monitoring, treatment, alleviation or compensation of injuries or handicaps,
• investigation, replacement or modification of the anatomy or of a physiological process,
• control of conception.

As this guidance was published before the current MDR entered into force, Article 2 (1) of the MDR [17] replaces the outdated purposes of the Act on Medical Devices. In summary, based on the legal definitions, mobile medical apps are medical devices and, therefore, are intended to be used for medical purposes. Thus, the key phrase is the intended use [44].

DiGA Definition

Closely related to medical apps are DiGA, which are officially available for prescription in Germany since October 2020. The law itself defines DiGA as “medical devices of lower risk class [intended to] support the detection, monitoring, treatment or alleviation of disease or the detection, treatment, alleviation of, or compensation for, an injury or disability of insured people” (own translation [45]).

Referring to medical devices, the definition of DiGA reveals that the intended use is again essential for their definition. Hence, DiGA are a small subset of mobile medical apps and medical devices. Spoken more abstractly, all DiGA are medical apps—and, therefore, medical devices—but not all medical devices and medical apps are DiGA. DiGA are predominantly regulated by the German Medical Device law and are only offered when they fulfill the Digital Health Applications Ordinance requirements regarding, for example, quality and safety, data protection, and data security.

DiPA Definition

Shortly after introducing DiGA, the German legislature regulated so-called DiPA in January 2022. According to the law, DiPA are “applications that are essentially based on digital technologies and are used by those in need of care or the interaction of those in need of care, relatives, and approved outpatient care facilities to reduce impairments to the independence or abilities of the person in need of care and to counteract a worsening of the need for care, insofar as the application is not to be provided by the health insurance or other responsible service providers due to illness or disability (digital care applications)” (own translation [46]).

Unlike DiGA, DiPA can but do not necessarily have to be medical devices. This affects the health aim of DiPA as well—DiGA need to be medical devices and, thus, have to be intended by the manufacturer to be used for medical purposes. However, DiPA do not need this health aim as they focus on care and the reduction of impairments or abilities of care recipients. According to the legislator, a DiPA can sometimes cover the same purposes as a DiGA [46], which implies that DiPA can be used for medical purposes. Through this statement, the legislator classifies care as a possible medical purpose.

Nevertheless, delimitation questions appear when an app addresses medical and care purposes. In addition, DiPA can include medical apps that cannot be reimbursed as DiGA. DiGA are limited to medical devices of a lower-risk class (according to the risk classes of the MDR), whereas DiPA can also include those of higher-risk classes. As the DiPA regulation was just passed at the time this paper was written, the distinction between DiPA and DiGA is not clear yet. It is presumed that it will be part of the former DiPA ordinance—the equivalent of the Digital Health Applications Ordinance.

Summary of the Legal Landscape

Legal norms and guidance only contain the terms medical devices, mobile medical apps, DiGA, and DiPA. They do not include the term health app. Consequently, there are only legal definitions of medical devices, mobile medical apps, DiGA, and DiPA. Except for DiPA, these definitions directly share one key characteristic: the intended use for medical purposes. As the legislator implies that caring is a medical purpose, DiPA indirectly share the intended use for medical purposes.

However, the question remains as to which aspects are regulated by the named laws. The regulation of medical devices, mobile medical apps, and DiGA is part of the Medical Device Law. Accordingly, the Federal Food, Drug, and Cosmetic Act and the MDR set high quality and safety standards for medical devices to meet everyday safety concerns. Medical devices need to fulfill special requirements to enter the market. For example, the MDR stipulates the supervision of notified bodies, conformity assessment procedures, clinical investigations, clinical evaluation, vigilance, market surveillance, transparency, and traceability [47].

Scientific Definitions

Overview

Our search produced a total of 22 papers providing a definition of health apps and 11 papers that defined medical apps in English or German (the total number of included papers was 24). No original definitions in Chinese were identified (the only definition coming from a Chinese publication [48] was published in English). We identified more papers providing a description. For example, Karakoyun et al [49] referred to the FDA definition of medical apps [42]. In contrast, Azad-Khaneghah et al [50] cited the definition of health apps by Morse et al [51], and Sun et al [52] used the description of health apps by Aitken and Lyle [53]. However, all these other papers referenced definitions from the papers included in our corpus. Hence, they were not included in our final data set.

The included original definitions are presented in Table 1. Where publications provided a definition of both health and medical apps, the definitions are displayed next to each other to make differences more visible.

Quality Analysis of Found Definitions From Scientific Papers

We analyzed the identified definitions using MAXQDA to form word clouds of the terms used for health apps and medical apps. Multimedia Appendix 1 provides a brief overview of the differences in wording of health and medical apps (for word cloud data, see also Multimedia Appendix 1). The following sections provide a more detailed analysis of the definitions’ topics.

Health Apps

Our qualitative analysis identified the 7 most common topics (user, health aim, definition of health, device, regulation, data, and technological functions) addressed by most publications for health apps. For health apps, the 2 dominant topics were the health aim of health apps and the used or produced data. Only a few definitions (2/22, 9%) addressed the missing regulation and the functions of the apps (Multimedia Appendix 2 [21,35,48,51,53-58,60-66,68-72]).

Except for 9% (2/22) of the publications [54,72], every definition addressed the aim of health apps. A total of 45% (10/22) of the papers [35,51,56-58,62-65,68] named health promotion as a goal of health apps. Other frequently given aims included improving the user’s fitness [21,56,60,62,66], wellness [21,35,53,60,61,63], and mental and social well-being [55,60,65]. Less frequently stated were the health aims disease prevention and disease management [53,69]; illness or disease self-management [53]; behavior tracking [70]; access to health information; psychological support; and decision-making support to facilitate collaboration between the patient, their family, and their physician [69]. More generally, Tobias and Spanier [72] spoke about health conditions.

The user group was described in 64% (14/22) of the papers. Although 21% (3/14) of these papers mentioned users in general [48,63,64], 29% (4/14) limited this group to health-conscious users [68], (healthy) users who are interested in health [21,35], or medical laypersons interested in health [66]. Similarly, mentioned user groups of health apps were citizens [65] and individuals [58,63,70], patients [56,65,69,71,72], or the family as a potential user group [69]. Only 29% (4/14) of the definitions named professionals (ie, non-healthcare professionals [68], health professionals [69], or physicians [72]) as users of health apps.

A total of 64% (14/22) of the publications included data collection in their definition of health apps. However, the types of data collected were heterogeneous. In total, 36% (5/14) of the papers stated that health apps collect data on health behavior [35,54,57,62,70]. Other publications reported data on physical activity (4/14, 29%) [35,56,57,60] or dietary data (4/14, 29%) [56,57,66,69]. Some definitions restrained themselves from naming concrete fields and were phrased more generically as collecting general information about their body (1/14, 7%) [21], other parameters related to health (1/14, 7%) [54], health outcomes (1/14, 7%) [51], health conditions (2/14, 14%) [69,72], physiological data (1/14, 7%) [71], or health-related data (1/14, 7%) [68].

Concerning devices, of the 12 papers that defined health apps, 6 (50%) described health apps as mobile applications in their definitions [51,55,60,65,66,71]. Some publications described health apps as mobile phone (2/12, 17%) [54,57]; smartphone (3/12, 25%) [64,70,71]; or, more generally, as mobile device based (3/12, 25%) [54,61,64]. Only 8% (1/12) of the papers included tablets as devices for health apps [64].

In total, 41% (9/22) of the papers described the technical functions of health apps. These included tracking [54,66,70,71], data collection [66,68,71], recording [56,68,71], exercise assistance [56,60], monitoring [69,72], detection, connecting, measuring, and uploading [54]. A total of 5% (1/22) of the papers each added the role of a diary [56], prescribing tools [60], providing continuous feedback [70], alerting [72], or more general tools for processing and visualizing data [68].

In total, 18% (4/22) of the papers (all from German authors) included a definition of health in their description of health apps [21,55,63,65]. All of them (4/4, 100%) referred to the definition given by the WHO in 1948, which framed health as “a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity” [73]. The regulation of health apps was addressed by only 9% (2/22) of the definitions [66,68]. Both publications stated that health apps are not subject to regular quality control [66] or not generally subject to any specific, binding regulation [68].

Medical Apps

In the definitions of medical apps, the common topics were similar to those of health apps. In contrast to health apps, no publication on medical apps defined medicine. Therefore, only 6 recurring issues in the descriptions of medical apps were identified. The reports on medical apps most often stated the health aim of the app and the user groups. Only 9% (1/11) of the definitions specified the data and function of medical apps (Multimedia Appendix 2).

In total, 91% (10/11) of the definitions described that the health aim of medical apps is to serve as clinical tools for detection, diagnosis, monitoring, and treatment of diseases or injuries [21,35,54,56,60,62,64,66,67] and decision support for medicine and nursing [21,35,54]. A total of 36% (4/11) of the definitions also stated that medical apps serve as self-management tools for chronic diseases and empowerment of patients [35,54,62,65,67]. In total, 18% (2/11) of the definitions mentioned the preventional purpose of medical apps [21,60].

Of the 11 definitions, 9 (82%) addressed users of medical apps. Most of the definitions commonly indicated that the users of medical apps are medical professionals (3/11, 27%) [21,64,67], medical service providers (1/11, 9%) [65], health care professionals (7/11, 64%) [21,35,56,59,62,66,67], and patients (7/11, 64%) [21,35,56,59,62,65,67]. A total of 9% (1/11) of the definitions included the general public in the user group [59]. Another definition specifically pointed out that patients’ family members (eg, in their function as guardians or caretakers) are also part of the medical app user group [35].

Only 27% (3/11) of the papers defined medical apps as mobile applications or software that operate on mobile devices, including smartphones and tablets [59,66,67], or smartwatches [67]. Equally less often addressed was the data criterion. Only 9% (1/11) of the definitions stated that medical apps collect health-related information [54], whereas no other publication described the data or technological functions of medical apps. In total, 18% (2/11) of the papers stated that medical apps are regulated as medical devices in Germany and the United States [64,66]. We described the legal regulation of medical apps as medical devices in detail in the previous section.

Discussion

Many of the definitions identified through the literature search addressed the criteria user group, a specific understanding of the term health, a concrete device, the fragmentary regulation of medical apps (or the lack of regulation for most other types of health apps), data collected, or technological functions to gather or display content within the app. A definition of health and medical apps should reflect this structure by using these criteria.

Definition of Health Apps

The health aim of health apps can be summarized as maintaining, improving, or managing the user’s health. However, it remains unclear what health means. Although none of the definitions of medical apps are built on a definition of health or medicine, some health app definitions (4/22, 18%) included their understanding of health. Although 18% (4/22) of the papers mentioned a definition of health [21,55,63,65], they all followed the WHO definition of health from 1948. On the basis of this definition, “health is a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity” [73]. Although there is no consensus on what aspects the term health entails, many authors see the WHO definition as outdated [74-77]. It is criticized for defining health as binary (complete health or no health) and, therefore, as a utopian status that cannot be achieved [77]. When we use the term health (aim), we consequently do not understand health as a binary construct, as the WHO defined it once. Instead, we see health as the “capability to cope with and to manage one’s malaise and well-being conditions” [75]. This capability is affected by potential limitations of the social, biological, physical, or interpersonal environment [78].

Building on the literature, health apps are software programs on mobile devices that process health-related data on or for their user. Every health-conscious individual can use them, be it medical laypersons, family caregivers, or health professionals, to maintain, improve, or manage the health of an individual as well as communities or the whole population of a country (such as COVID-19–tracing apps). Data processing, in our understanding, includes any operation performed on personal data (eg, collecting; organizing; storing; adapting; visualizing; retrieving; disseminating or otherwise making it available; restricting; or erasing) according to the General Data Protection Regulation [79].

Definition of Medical Apps

Medical apps are generally used for clinical and medical purposes and can but do not have to be legally regulated as mobile medical devices. From a public health perspective, they focus on secondary (early diagnosis and treatment of acute diseases or injuries) and tertiary (rehabilitation and management of chronic diseases) prevention. Nevertheless, the health aim of medical apps leads to the problem that some health apps (eg, fitness trackers or diary apps) could be seen as medical apps when used for self-monitoring by people with chronic illnesses. This would turn the health app into a medical app. To avoid delimitation questions, we propose integrating the manufacturer’s intention into the health aim of the app (see the legal definition of medical devices). Accordingly, medical apps are intended for medical purposes, which is stated in the app’s description, privacy policies, or terms and conditions. Thus, we propose the following holistic definition of medical apps: Medical apps are a subgroup of health apps that focus on secondary and tertiary prevention. They share the same technological functions (processing of health-related data) as health apps, and can be used on mobile devices. The main target groups (but not exclusively) are health professionals, patients, and family caregivers.

Following the legal definitions of DiPA and DiGA, both are subgroups of medical apps. DiGA must necessarily be used for medical purposes as they are medical devices. As the legislator implies that caring is a medical purpose, DiPA indirectly share the intended use for medical purposes, too.

Health-Related Apps

We identified a third group of apps during the literature search for definitions of health and medical apps: health-related apps. This relatively vague term was used in different publications [4,25,80]. It remains unclear to what extent this type of app is related to health and whether apps within this group are homogeneous enough for an umbrella definition. We want to emphasize that the term health-related app should not be used as a category because of its fuzzy nature. This term displays the uncertainty within the scientific community of what a health app is and, therefore, expresses the need for a clear definition.

Relationship Between Health and Medical Apps

Our findings regarding the differentiation between health and medical apps (and the 2 exceptional German cases of DiGA and DiPA) are displayed in Figure 2. Comparing the definitions of health apps with those of medical apps, we recognized that some criteria are equally relevant for both types of apps (ie, definition criteria), whereas others are not (ie, distinction criteria). The criteria device, collected data, and technological function are the definition criteria as they are equal for health and medical apps. In addition, regulation should not be a distinction criterion either. Defining medical apps by the way they are regulated requires legal knowledge, which is neither suitable nor practical for a definition and cannot be expected from all stakeholders.

On the contrary, the user group is a distinction criterion for the main user group. Equally, the health aim of an app is a distinction criterion. This leads to our understanding of health apps as the umbrella term, which includes medical apps as a subgroup.

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Decision Flowchart for Health and Medical Apps

On the basis of our analysis of the definitions derived from scientific literature and the legal regulations in the United States, the EU, and Germany, we designed a flowchart to classify health and medical apps (Multimedia Appendix 3).

Most of the definitions of medical apps given by scientific papers (6/11, 55%) matched the legal regulations in the United States and the EU insofar as they listed medical purposes (if they did not, it was because the scientific descriptions were not as specific as the legal papers). Owing to this finding, the flowchart offers insights on health and medical apps based on the legal definitions in the United States and the EU. However, it does not provide insights into whether an app is legally regulated. Instead, it showcases a specific app that fits the legal definitions in the named regions. However, other countries might have different legal regulations for mobile medical apps, so this flowchart can only report on the 2 regions given as case studies. The decision tree is intended to provide a low-threshold and practical way to differentiate between health and medical apps quickly. Therefore, it can be used by scientists and developers, politicians, or users of health-related apps. Owing to the recent introduction of DiPA, a concrete regulatory framework for these apps is still missing in Germany. As such, the flowchart does not include DiPA.

However, it is still unclear whether there will be more health-specific legal definitions once other countries begin regulating apps, similar to how Germany regulates DiGA and DiPA. Furthermore, it is unknown how app stores define and use the terms health app and medical app in their app categorization. Building on these questions, it is also unclear how the many different definitions affect the various stakeholders. It is yet to be examined what specific user groups expect from health and medical apps and how they would define both (eg, do health-conscious people or family caregivers want to use them in their daily lives?). It is also not evident whether prescribed apps affect the health care systems in any way and whether they improve health care. Finally, it remains unclear how we can ensure that health apps do not harm their users as most of them are unregulated. Further research needs to be conducted to answer all these questions.

Strengths and Limitations

To our knowledge, this is the first study to use an interdisciplinary approach to differentiate between health and medical apps from a legal and scientific point of view. By analyzing various sources, we provided an interdisciplinary and international overview of the multiple uses of the terms health app and medical app. The in-depth discussion of the scientific and legal perspective on health and medical apps offers a more holistic and deeper understanding of the similarities and differences between these terms. We conducted a qualitative analysis using the MAXQDA software to ensure the transparency of the analysis process of the identified definitions. To present the results of our approach, we incorporated our research findings into the creation of a decision chart (Multimedia Appendix 3). This may not only assist researchers in fostering a shared and clear understanding of the terms but also enable practitioners to interpret the findings of our study efficiently.

We do recognize that our research is prone to certain limitations. First, we applied the snowballing method in line with Wohlin [32]. However, although using a systematic collection technique [81] might have yielded different results, one of the key strengths of this review is its diversity of included disciplines and breadth of content. Hence, as the goal of our study was to be as inclusive as possible and analyze a wide range of fields and databases, the snowballing method was the most feasible option. Furthermore, we excluded gray literature that was not cited in our references or displayed the legal regulation in regions other than the United States or the EU. The same applies to the descriptions of apps in the app stores. We deemed this approach appropriate as the focus was on using the terms in science. However, scientists and policy makers are not the only parties involved in developing apps for health. Other stakeholders, such as developers or users, may have a scientific education but may struggle to discern health and medical apps represented in scientific publications. Subsequent research should be dedicated primarily to these sources to incorporate practitioners and other legal perspectives into our definitions of health and medical apps. It should further be noted that we only included literature published in Chinese, English, or German. Economically speaking, a large part of the health and medical app market is in the Asian region (eg, Japan). Therefore, from a global perspective, our research is undoubtedly fragmentary. Finally, it should be noted that this study does not report whether other publications used the identified scientific definitions.

Conclusions

With our literature review and qualitative analysis of the scientific definitions of health and medical apps and the legal perspective on medical apps, we offered the first step toward defining health and medical apps more holistically—health apps are software programs on mobile devices that process health-related data on or for their users. Every health-conscious individual can use them, be it medical laypersons, family caregivers, or health professionals, to maintain, improve, or manage an individual’s and the community’s health. As an umbrella term, health apps include medical apps.

Medical apps can be defined as a subgroup of health apps that have the same technological functions (processing health-related data) as health apps and can be used on mobile devices. The main target user groups (not exclusively) include health professionals, patients, and family caregivers. Medical apps share the intended use for clinical and medical purposes and can be legally regulated as mobile medical devices. From a public health perspective, they focus on secondary (early diagnosis and treatment of acute diseases or injuries) and tertiary (rehabilitation and management of chronic diseases) prevention. For the special case of Germany, medical apps include DiGA and DiPA.