Evidence-based medicine and the promises and limits of digital health and wearable technology

New approaches to biomedical evidence are emerging in relation to innovative technologies and data sources. These include digital health, which promises to revolutionise established paradigms such as Evidence-Based Medicine (EBM) and address longstanding criticism from philosophy and beyond. In this paper, we investigate the promises and show the limitations of digital health for the epistemology of medicine. Focusing on a paradigmatic type of digital health technologies - wearable devices - we specify the key epistemic assumptions at the basis of digital health and show their grounding on ideas of internal and external validity that come from EBM and promise to fix its limitations. Hence, digital health is expected to address longstanding issues of EBM and expand and reinforce its paradigm, and yet going in this direction exacerbates and creates concerns for the epistemology of medical evidence, with ethical and social implications too. In observational studies, we show that wearables are used with the assumption of extending EBM approaches to internal validity. Yet new and different issues emerge, leading to complicated trade-offs and concerns about overdetection and high false positive rates. In intervention studies, wearables are used with the assumption of creating a larger and more diverse evidential basis, potentially mitigating concerns about external validity. However, we argue that this can exacerbate and create new issues of representativity. Behind the hype, we thus paint a nuanced picture of the contribution of digital health to EBM and biomedical research and show the need to acknowledge limitations to avoid harmful applications.