Questioning Personalised Health: Limitations of Interpreting Wearable Data at the Individual Level

Wearable technologies are increasingly used to support personalised health management and promote health-related behaviours. These devices generate continuous, real-time data that are often interpreted as individualised health information. However, the key issue is not only data accuracy, but whether wearable-derived metrics are valid at the individual level or truly reflect personalisation. While wearable data may appear precise, their interpretation is limited by measurement variability, lack of contextualisation, and reliance on population-based models. This paper introduces the concept of the illusion of personalisation to describe the discrepancy between the apparent specificity of wearable-derived data and their limited individual-level interpretability. Data alone do not create meaning, and additional data do not necessarily improve clarity. In health promotion and preventive medicine, uncritical interpretation of wearable data may overestimate their clinical relevance. A cautious approach is therefore warranted, recognising wearable data as indicators of general trends rather than definitive representations of individual health.