Feasibility assessment of smartwatch based ecological momentary assessment of mood, with concurrent smart ring assessment of sleep and physical activity.

Background: Digital phenotyping offers opportunities to capture real-time behavioral and physiological markers associated with mood disorders. For example, sleep and physical activity are two key behavioral exposures consistently shown to reduce risk for depression and anxiety symptoms. However, feasibility and acceptability challenges, particularly relating to device burden and data reliability, remain barriers to upscaling sample sizes.Objective: This mixed-methods feasibility study evaluated the acceptability, usability, and data completeness of passive monitoring of sleep and physical activity via a smart ring and active ecological momentary assessment (EMA) of mood and contextual factors via a smartwatch in adults from the general population.Methods: Participants wore a consumer-grade Oura smart ring to passively track sleep and physical activity for 2 weeks while concurrently completing brief mood EMAs on a study-issued smartwatch. Feasibility metrics included device adherence, EMA completion rate, and patterns of missingness. Acceptability was assessed through semi-structured interviews. Exploratory analyses examined associations between daily mood, sleep and physical activity.Results: Adherence to both devices was high, with participants wearing the ring consistently and completing most EMA prompts (mean compliance = 90%, range = 90.1%75.0%-100%). The smartwatch delivered a higher number of prompts than originally scheduled and showed some variability in timing of prompts. Furthermore, qualitative interviews indicated strong preferences for the smart ring, described as comfortable and unobtrusive, while the watch was experienced as bulky, with participants reporting difficulties managing two devices. There was no difference in the patterns of data missingness by time of day or day of the week. Mood ratings demonstrated reasonable variability, but exploratory associations between mood and either physical activity or sleep were not detected, likely due to limited power.Conclusions: Passive monitoring via a smart ring was highly feasible and acceptable, whereas smartwatch EMA was less popular with participants, suggesting that smart rings might be better used in conjunction with smartphone-based EMA. Future studies should consider rings for scalable passive data collection and ensure robust EMA scheduling mechanisms. Scaling this protocol up into larger samples is likely required to evaluate mood–behavior associations.