JMIR Publications

ABSTRACT

Background:

Drink Less is a behaviour change app to help higher risk drinkers in the UK reduce their alcohol consumption. The app includes a daily notification, asking users to “Please complete your drinks and mood diary”, yet we did not understand the causal effect of the notification on engagement nor how to improve this component of Drink Less. We developed a new bank of 30 new messages to increase users' reflective motivation to engage with Drink Less. In this study we aimed to determine how both the standard and new notifications affect engagement.

Objective:

Our objective was to estimate the causal effect of the notification on near-term engagement, to explore whether this effect changed over time, and to create an evidence base to further inform optimisation of the notification policy.

Methods:

We conducted a Micro-Randomised Trial (MRT) with two additional parallel arms. Inclusion criteria were Drink Less users who (1) consent to participate in the trial; (2) self-report a baseline Alcohol Use Disorders Identification Test score of 8 or above; (3) reside in the United Kingdom; (4) age ≥18 years and (5) report interest in drinking less alcohol. Our MRT randomised 350 new users to test if receiving a notification, compared to receiving no notification, increased the probability of opening the app in the subsequent hour, over the first 30 days since downloading Drink Less. Each day at 8 PM, users were randomised with 30% probability to receive the standard message, 30% probability to receive a new message or 40% probability to receive no message. We additionally explored time-to-disengagement, with the allocation of sixty percent of eligible users randomised to the MRT (n=350), and forty percent of eligible users randomised in equal number to the two parallel arms, either receiving the no notification policy (n=98) or the standard notification policy (n=121). Ancillary analyses explored effect moderation by recent states of habituation and engagement.

Results:

Receiving a notification, compared with not, increased the probability of opening the app in the next hour by 3.5-fold (95% confidence interval (CI) 2.91, 4.25). Both message types were similarly effective. The effect of the notification did not change significantly over time. A user being in a state of ‘already engaged’ lowered the new notification effect by 0.80 (95% CI 0.55, 1.16), though non-significantly. Across the three arms, time-to-disengagement was not significantly different.

Conclusions:

We found the notification has a strong near-term effect on engagement but no overall difference in time to disengagement between users receiving the standard fixed notification, no notification at all, or the random sequence of notifications within the MRT. The strong near-term effect of the notification presents the opportunity to target notifications to increase ‘in-the-moment’ engagement. To improve longer-term engagement, further optimisation is required. Clinical Trial: International Registered Report Identifier (IRRID): DERR1-10.2196/18690