JMIR Publications

ABSTRACT

Background:

Micro-randomised trials (MRTs) have emerged as the gold standard for the development and evaluation of multi-component, adaptive mobile health (mHealth) interventions. However, not much is known about the state of participant engagement measurement in MRTs of mHealth interventions.

Objective:

In this review, we aimed to quantify the proportion of existing/planned MRTs of mHealth interventions to date that have assessed (or have planned to assess) engagement. For trials that have assessed (or have planned to assess) engagement, we also aimed to investigate how engagement has been operationalized and to identify what kind of factors have been studied as determinants of engagement in MRTs of mHealth interventions.

Methods:

We conducted a broad search for MRTs of mHealth interventions in 5 databases and manually searched preprint servers and trial registries. Study characteristics of each included evidence source were extracted. We coded and categorized this data to identify how engagement has been operationalized and which determinants, moderators, and control variables have been assessed in existing MRTs.

Results:

Our database and manual searches yielded 22 eligible evidence sources. Most of these studies were designed to evaluate the effect of intervention components on health outcomes (14/22 studies). The median sample size of the included MRTs was 110.5. At least one measure of engagement was included in 90.91% (20/22 studies) of the included MRTs. Engagement operationalized as usage (16/20; 80%) was most prevalent followed by responsiveness (11/20; 55%), practice (6/20; 30%), and then comprehension (1/20; 5%). Only 6 of the 20 studies to measure engagement (30%) assessed the determinants of engagement in MRTs of mHealth interventions – notification-related variables were the most common determinants of engagement assessed (4/6 studies). Three of these studies also examined the moderators of participant engagement – 2 studies investigated time-related moderators exclusively and 1 study planned to investigate a comprehensive set of physiological and psychosocial moderators in addition to time-related moderators.

Conclusions:

Although the measurement of participant engagement in MRTs of mHealth interventions is prevalent, there is a need for future trials to strike a balance between measuring engagement as usage/responsiveness and as practice. There is also a need for researchers to address the lack of attention to how engagement is determined and moderated in MRTs of mHealth interventions. We hope that by mapping the state of engagement measurement in existing MRTs of mHealth interventions, this review will encourage researchers to pay more attention to these issues when planning for engagement measurement in future trials.