Who benefits from computer-based brief alcohol intervention? Day-to-day drinking patterns as a moderator of intervention efficacy

Objective to test if people with different day-to-day drinking patterns benefitted differently from two brief alcohol interventions (BAIs). Methods A total of 1243 job-seekers with at-risk alcohol use aged 18–64 years (64% men) were randomized to (a) intervention tailored to the motivational stage (ST), (b) non-stage tailored intervention (NST), or (c) assessment only (AO). ST and NST contained individualized computer-generated feedback letters. Follow-ups were conducted at months 3, 6, and 15. Using growth mixture models, day-to-day drinking patterns were identified based on the number of drinks consumed on each day in the week prior to baseline assessment. To test drinking pattern-specific intervention effects, zero-inflated growth models were used. Outcomes were (1) the 15-month change in the likelihood of any alcohol use and (2) the 15-month change in the total number of drinks per week when alcohol was consumed. Results Four day-to-day drinking patterns were found: daily medium use (2–4 drinks/day; 47%), daily low use (1–2 drinks/day; 29%), weekend only use (18%), and no use (6%). Only persons with daily low use benefitted from intervention, with higher odds of being abstinent after 15 months in the ST group compared to AO (odds ratio, OR = 1.67, p = 0.001) and NST group (OR = 1.43, p = 0.035). ST worked better among persons with daily low use compared to daily medium use (OR = 1.91, p = 0.001). Conclusions Among at-risk drinking persons with regular low-quantity alcohol use, stage tailored BAIs may be superior over no BAI and non-stage tailored BAIs.