Evaluating the effectiveness of the Drink Less smartphone app for reducing alcohol consumption compared with usual digital care: a comprehensive synopsis from a 6-month follow-up RCT

Background

Digital interventions can be effective for reducing alcohol consumption. However, most digital interventions that have been evaluated are websites and there is little evidence on the effectiveness of smartphone apps, especially in a United Kingdom context. We developed an evidence- and theory-informed app, Drink Less, to help increasing-and-higher-risk drinkers (Alcohol Use Disorders Identification Test score ≥ 8) reduce their alcohol consumption.

Objective

To evaluate the effectiveness of Drink Less for reducing alcohol consumption compared with usual digital care in the United Kingdom.

Design

Two-arm, double-blind, parallel-group, randomised controlled trial with 1 : 1 group allocation and an embedded process evaluation, with 6-month follow-up.

Setting

Remotely conducted among participants living in the United Kingdom, recruited from July 2020 to March 2022.

Participants

Five thousand six hundred and two increasing-and-higher-risk drinkers aged 18+ who had access to an iPhone operating system device and wanted to drink less alcohol.

Interventions

Participants were recommended to use the intervention (Drink Less) or recommended the comparator (National Health Service alcohol advice web page).

Drink Less is an app-based intervention to help increasing-and-higher-risk drinkers reduce their alcohol consumption. It consists of evidence-based modules (e.g. goal setting, self-monitoring) and was systematically and transparently developed and refined.

The National Health Service alcohol advice web page was considered usual digital care and provides tips on cutting down.

Main outcome measures

The primary outcome was self-reported weekly alcohol consumption at 6-month follow-up (derived from the extended Alcohol Use Disorders Identification Test – Consumption), adjusted for baseline alcohol consumption.

Results

The retention rate at 6-month follow-up was 80%. The data were not missing completely at random with differences detected in educational qualifications, occupation and income, indicating that multiple imputation was the most appropriate analytic approach. This found that Drink Less resulted in a 2.00 United Kingdom unit greater weekly reduction (95% confidence interval −3.76 to −0.24) at 6-month follow-up compared with the National Health Service alcohol advice web page. Compared with the National Health Service alcohol advice web page, Drink Less cost an additional £1.28 per user, when including the sunk costs (already incurred and cannot be recovered), but saved £0.04 per user when considering only the annual maintenance costs. Drink Less costs only an extra £0.64 per additional weekly unit of alcohol reduction, and may be cost saving if sufficient people use the app to cover the sunk costs. There was no statistically significant difference in quality-adjusted life-years between the two groups.

Limitations

This trial relied on retrospective self-reported alcohol consumption. Results from the pre-registered sensitivity analysis of multiple imputation were inconsistent with those from the pre-registered primary analysis (a conservative approach to missing data where non-responders were assumed to be drinking at baseline levels), which found a non-significant weekly reduction of 0.98 units (95% confidence interval −2.67 to 0.70) in the intervention compared with comparator group. Multiple imputation was recommended by the independent Data Monitoring Committee based on the pattern of missing data.

Conclusions

Drink Less appears effective for reducing alcohol consumption among increasing-and-higher-risk drinkers compared with the National Health Service alcohol advice web page in the United Kingdom, and may be cost saving if widely used in the population.

Future work

Drink Less is in a strong position to be promoted widely and provide inexpensive support to increasing-and-higher-risk drinkers in the United Kingdom. Future work should investigate different promotion strategies and ways of implementing the app within healthcare settings and adapting it for other countries.

Funding

This synopsis presents independent research funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme as award number NIHR127651.