INTRODUCTION Concurrent users of tobacco and alcohol are at greater risk of harm than use of either substance alone. It remains unclear how concurrent tobacco and alcohol use affects smoking cessation across levels of alcohol use and related problems. This study assessed the relationship between smoking cessation and levels of alcohol use problems.

METHODS 59,018 participants received nicotine replacement therapy through a smoking cessation program. Alcohol use and related symptoms were assessed using the Alcohol Use Disorders Identification Test (AUDIT-10) and the AUDIT-Concise (AUDIT-C). The primary outcome was 7-day point prevalence cigarette abstinence (PPA) at 6-month follow-up. We evaluated the association between alcohol use (and related problems) and smoking cessation using descriptive methods and mixed-effects logistic regression.

RESULTS 7-day PPA at 6-months was lower in groups meeting hazardous alcohol consumption criteria, with the lowest probability of smoking abstinence observed in the highest risk group. The probability of successful tobacco cessation fell with increasing levels of alcohol use and related problems. Adjusted predicted probabilities were 30.3 (95 % CI = 29.4, 31.1) for non-users, 30.2 (95 % CI = 29.4, 31.0) for low-risk users, 29.0 (95 % CI = 28.1, 29.9) for those scoring below 8 on the AUDIT-10, 27.3 (95 % CI = 26.0, 28.6) for those scoring 8-14, and 24.4 (95 % CI = 22.3, 26.5) for those scoring 15 or higher.

CONCLUSION Heavy, hazardous alcohol use is associated with lower odds of successfully quitting smoking compared to low or non-use of alcohol. Targeting alcohol treatment to this group may improve tobacco cessation outcomes.