Epistemic agency in self-tracking: a conceptual literature review of quantified self as citizen science for health.

INTRODUCTION: Citizen science for health invites non-professionals into research, but the degree to which individuals control the knowledge-making process varies widely. Personal science-the self-directed, inquiry-driven practice associated with the Quantified Self (QS) community-represents a high-agency form of self-tracking in which the individual is both subject and scientist. Drawing on work on epistemic injustice, we use "epistemic agency" to describe whether a person exercises genuine control over inquiry rather than merely supplying data. AIM: To assess the utility of an agency-based framework for characterizing the epistemic dimension of self-tracking, and to examine how personal science has been represented in the scientific literature. METHODS: Following Jaakkola's theory-synthesis approach, we developed a four-phase analytical framework (questioning, observing, reasoning, discovering) with three levels of individual agency (low agency, mixed agency, high agency). A search of Web of Science and PubMed (April-May 2025) for "quantified self" yielded 721 records; 241 were retained for analysis, of which 46 used self-tracking as the data-collection method and were classified by agency level through independent dual-author review. RESULTS: The 46 articles spanned the full agency spectrum: 17 low, 10 mixed, and 19 high. Low-agency studies treated individuals as data sources, whereas high-agency studies displayed the complete self-directed cycle, often with the self-tracker as co-author. Data-sharing dominated low-agency accounts, while sharing of methods and experiences characterized higher-agency work. CONCLUSION: The framework can meaningfully distinguish merely measurement from self-directed knowledge production, turning on who owns the question. Personal science can be seen as a high-agency dimension of citizen science for health.