Military DrinksRation: a randomized controlled trial of a smartphone intervention to reduce alcohol consumption among regular UK Armed Forces personnel

<title>Abstract</title> <p> <bold>Introduction</bold> Alcohol misuse remains a significant cause of morbidity among serving UK Armed Forces (UKAF) personnel, with prevalence exceeding that of comparable civilian populations. Digital interventions offer a potentially scalable approach to alcohol reduction, and the DrinksRation smartphone application has previously demonstrated effectiveness among UK military veterans. This study evaluated the effectiveness of DrinksRation in reducing alcohol consumption among serving UKAF personnel drinking at levels which risk alcohol related harm. <bold>Methods</bold> Military DrinksRation was a two-arm, parallel-group, superiority randomised controlled trial nested within the Drinking and Wellbeing study. Serving UKAF personnel screening positive for at-risk drinking (Alcohol Use Disorders Identification Test-Consumption (AUDIT-C) score &gt; 4) were randomised to receive either the DrinksRation smartphone application or treatment as usual. The primary outcome was alcohol consumption at 84 days. Secondary outcomes included motivations for drinking, barriers to changing alcohol use, common mental disorders and loneliness. Recruitment took place between October 2023 and July 2024. <bold>Results</bold> A total of 613 serving personnel completed AUDIT-C screening, of whom 338 (55.1%) met the eligibility criteria for the trial. 113 participants were randomised (58 treatment as usual; 55 DrinksRation). Personnel screening positive for at-risk drinking were significantly less likely to consent to participate than those drinking at lower risk levels (33.4% vs 42.2%; χ ²  = 4.96, <italic>p = 0.03</italic> ). Recruitment and follow up were substantially lower than anticipated with no participants in the intervention arm completing the primary end point assessment at 84 days. Consequently, the prespecified comparative analyses of the primary and secondary outcomes could not be undertaken. Participants who activated the DrinksRation application demonstrated sustained engagement with the intervention despite poor completion of research follow up assessments. <bold>Conclusions</bold> The trial did not generate sufficient outcome data to evaluate effectiveness. However, it demonstrates that routine screening can identify serving personnel drinking alcohol at risky levels, while recruitment, intervention activation and research follow-up remain substantial barriers to evaluating digital alcohol interventions in serving military populations. Although routine screening successfully identified personnel drinking at-risk of alcohol-related harm, engaging those individuals with research participation and sustaining follow up proved considerably more challenging. <bold>Trial registration</bold> ISRCTN 14977034 ¹ . Prospectively registered. The study protocol was published prior to commencement of recruitment ² . </p>