Feasibility and Acceptability of a Mindfulness App Intervention for Healthcare Worker Families Under Stress: A Pilot Micro-Randomized Trial

<b>Background:</b> This pilot study examined the feasibility, acceptability, usability, and preliminary outcomes of <i>apt.mind</i>, a mobile app-based mindfulness intervention with an exploratory smartwatch component, among healthcare worker families during the COVID-19 pandemic. <b>Methods:</b> Using a micro-randomized trial (MRT) design, 102 healthcare workers and co-parents of children aged 4-13 years were randomized once per day over 30 days to one of three conditions: (1) an audio-guided mindfulness exercise delivered via the <i>apt.mind</i> mobile app, (2) an in-app push notification prompting a brief mindfulness activity, or (3) no intervention. Feasibility was assessed through participant enrollment, retention, and daily engagement rates, while acceptability and usability were evaluated through qualitative and quantitative feedback. Exploratory multilevel analyses examined proximal effects of intervention conditions on momentary stress. <b>Results:</b> Retention was high, with all participants completing the 30-day protocol, and 80% of participants completed at least one daily survey. Participants reported moderate-to-high acceptability and usability. However, smartwatch battery life and sensor reliability limited the collection of usable physiological data. Multilevel analyses did not identify any significant main effects of intervention condition on momentary stress, but age moderated the association between the audio exercise condition and stress, benefiting older participants. <b>Conclusions:</b> Mobile-based mindfulness interventions appear feasible and acceptable for healthcare worker families in high-stress contexts. Although proximal stress effects were limited and exploratory, the findings inform future optimization of just-in-time adaptive interventions. Improvements in wearable technology and MRT implementation strategies are needed to enhance physiological data quality and reduce assessment-related anxiety.