Starting positionInexpensive sensors in portable devices and an increasing number of applications (apps) for lifestyle, wellness and health tracking allow users to record their physical activity and behaviour. This self-tracking has become known as Quantified Self (QS) and provides a wealth of data (big data) that does not only arouse hope for new insights in people using self-trackers but also in players in the health sector and the industry who likewise want to benefit from the data evaluations. However, little is known so far about the possible consequences, opportunities and risks for individuals, organisations and society arising from self-tracking technologies.TargetThe "Quantified Self - Interface between Lifestyle and Medicine" project is a study that aims to provide an overview of the current status of self-tracking as well as future trends. It assesses strengths and weaknesses as well as the opportunities and risks by taking into account the implications for social, medical, economic, technical, legal and ethical perspectives. These findings then enable the project team to issue recommendations for decision-makers that should serve to exploit the opportunities arising from the use of QS while controlling the associated risks.MethodsThe project is divided into the following four subprojects: (1) Current status and trend analysis, (2) User survey, (3) Overall assessment and recommendations, and (4) Dissemination of results.The aim of subproject (1) was to collect information on the current status and future developments of QS through literature and document review in the areas under investigation. This knowledge gained was then supplemented by interviews conducted with 19 experts on the subject. Subproject (2) explored the benefits and reasons for using and the implications of QS by assessing the perspectives of users and health professionals with focus group interviews, an online survey and the survey of a so-called QS user group. Subproject (3) constituted a workshop as a follow-up for the interdisciplinary analysis of the resultant findings in respect to opportunities and risks.The outcomes were evaluated in a subsequent overall assessment to draw specific recommendations for action for different decision-makers and stakeholders. Last but not least, subproject (4) deals with the dissemination of the research results.ResultsThere is no standardised definition of QS. Therefore, in the context of this study, the term is understood as follows: Quantified Self (QS) is characterised by the fact that a person actively tracks his or her activity through sensors on devices and applications to generate knowledge from data-based findings that help improve lifestyle and behaviour in areas such as fitness, wellness and health.The variety of devices and apps available for self-tracking can legally be divided into consumer and medical devices.Products for QS are considered consumer products, when they are used in the area of lifestyle, well-ness, fitness or health, and are regulated by Consumer Rights. Most of the products currently available on the market fall into this category. The use of medical devices, however, serves an intended medical purpose, which is why they are subject to the strict Swiss Therapeutic Products Act.The phenomenon of self-tracking is not an invention of modern times. Man has been monitoring himself for centuries, the best known example of this is body weight. From a social perspective, various developments have contributed to the importance of digital self-quantifying such as: new technologies, cultural changes and people's changing communication behaviours, which all lead to the greater importance of individualisation through its orientation towards the social ideal of self-optimisation and individual responsibility. Today, the body is seen as a result of personal achievement and no longer as a biological destiny. Personal economic awareness of individuals is gaining in importance and has implications in the shifting of the responsibility from health professionals to the individual in disease treatment and prevention and hence illustrates and underlines the paradigm shift in healthcare provision. Digital self-tracking is part of it and fosters its development.QS applications are already being tested in the medical field, especially in the treatment of chronic disease.However, the Swiss healthcare sector is still somewhat hesitant with regard to its use, even though QS applications are credited with great potential. The main reason for this is the lack of reliability in collected data, incomplete evidence regarding effectiveness and the lack of quality standards for existing devices and apps.Despite constantly improved sensor technology, the insufficient data security and the poor data quality of the products (wearables) constitute a major problem from a technical point of view. The large amounts of data and the aggregation of different data sources further represent a major technical challenge.From a business viewpoint, vendors of QS products and services are players in the healthcare sector and, increasingly, also commercial and telecommunication companies. Smartphones are the preferred hardware for tracking health data in Switzerland; wearables are much less common. The Swiss watch industry is increasingly cooperating with technology companies in order to remain competitive in the market with smartwatches. Health-related apps also show high growth rates. Just as for research, a number of economic players, such as insurance companies and the pharmaceutical industry, are equally interested in the collection of personal data by means of self-tracking.Foreign suppliers who want to market QS products in Switzerland frequently do not adhere to the regulatory requirements. Also, developers and providers who are new to the healthcare market often do not know or choose to ignore these standards. Customers frequently have to overcome high barriers to assert and enforce their claims in cross-border legal disputes with providers. This is equally true from a legal point of view as far as concerns inadequately guaranteed data protection from the manufacturers and service providers in the use of QS products through to the misuse of data.From a legal ethics point of view, different ideas prevail with respect to QS. Some authors consider QS a driver for innovation while others highlight the risks to values such as privacy, transparency, (informational) self-determination, equality and solidarity.Opportunities and risks of QS arise for (1) individuals, (2) institutions, organisations and companies, and (3) society as a whole and relate primarily to health, privacy and ethics. Today these risks do not necessarily indicate a need for action, especially if existing standards and law enforcement are sufficient to limit a fundamental risk. To benefit from the opportunities that QS applications offer, a few more steps have to be taken. These have been listed as explicit recommendations for action.