Moderators of the Effectiveness of a Brief Negotiation Intervention for Harmful Alcohol Use in Injured Adults at Northern Zone Referral Hospital in Tanzania

Abstract Background Harmful alcohol use is a leading global health risk, with a disproportionately high burden in Africa. A culturally adapted Brief Negotiation Intervention (BNI), “Punguza Pombe Kwa Afya Yako” (PPKAY), was developed in a prior study and demonstrated effectiveness in reducing harmful alcohol use among those who presented with trauma. This study aimed to evaluate BNI's effect on drinking days, drinks consumed, and binge drinking days, and to examine moderators of this effect, among injured adults presenting to Kilimanjaro Christian Medical Center (KCMC) Emergency Medicine Department (EMD). Methodology: This was a secondary analysis of the Stage 1 cohort (2020–2025) Pragmatic Randomized Adaptive Clinical Trial (PRACT). A total of 584 injured patients with harmful alcohol use were randomized to BNI (PPKAY) (n = 413) or Usual Care (n = 171). Outcomes were drinking days, drinks consumed, and binge drinking days at 3-month follow-up (Timeline Follow-back), as well as moderators for effective BNI. Mixed-effects zero-inflated negative binomial regression assessed the effect of BNI and nine moderators, with cluster-robust negative binomial regression as a sensitivity analysis. Results BNI (PPKAY) significantly reduced all three outcomes at 3 months versus Usual Care: drinking days by 58% (IRR = 0.42, p < 0.0001), drinks consumed by 65% (IRR = 0.35, p = 0.0001), and binge drinking days by 69% (IRR = 0.31, p = 0.0028). Only education moderated these effects (interaction p = 0.024, 0.018, 0.029). Drinking days fell by 71% (IRR = 0.29) with primary education or less, versus a non-significant 28% (IRR = 0.72) with secondary education or higher. BNI estimates favored intervention in every subgroup, with non-significant trends toward larger reductions among non-agricultural workers, married or partnered patients, and those with less serious injuries. Conclusions PPKAY reduced harmful alcohol use across all three outcomes and in every subgroup examined; education was the only significant modifier, with the largest reductions among patients with primary education or less. PPKAY should be integrated into routine emergency care for all injured patients, delivered verbally in Kiswahili by trained nurses, with SMS boosters evaluated for patients with secondary education or higher.