Background: Metabolic diseases, such as cardiovascular diseases and diabetes, contribute significantly to global mortality and disability. Wearable devices and smartphones increasingly track physiological and lifestyle risk factors and can improve the management of metabolic diseases. However, the absence of clear guidelines for deriving meaningful signals from these devices often hampers cross-study comparisons. Objective: Thus, this scoping review protocol aims to systematically overview the current empirical literature on how wearables and smartphones are used to measure modifiable risk factors associated with metabolic diseases. Methods: We will conduct a scoping review to overview how wearables and smartphones measure modifiable risk factors related to metabolic diseases. We will search six databases (Scopus, Web of Science, ScienceDirect, PubMed, ACM Digital Library, and IEEE Xplore) from 2019 to 2024, with search terms related to wearables, smartphones, and modifiable risk factors associated with metabolic diseases. We will apply the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) and Arksey and O'Malley's scoping review methodology. Eligible studies will use smartphones and/or wearables (worn on the wrist, finger, arm, hip, and chest) to track physiological and/or lifestyle factors related to metabolic diseases. Two reviewers will independently screen articles for inclusion. Data will be extracted using a standardized form, and the findings will be synthesized and reported qualitatively and quantitatively. Results: The study is expected to identify potential gaps in measuring modifiable risk factors in current digital metabolic health research. Results are expected to inform more standardized guidelines on wearable and smartphone-based measurements to aid cross-study comparison. The final report is planned for submission to an indexed journal. Conclusions: This review is among the first to systematically overview the current landscape on how wearables and smartphones are used to measure modifiable risk factors associated with metabolic diseases.

The authors have declared no competing interest.

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