Does alcohol consumption elevate smoking relapse risk of people who used to smoke? Differences by duration of smoking abstinence

Background: Past research indicates dual users of tobacco and alcohol find it harder to quit smoking and may be more likely to relapse. This study investigated whether post-quit alcohol use predicted smoking relapse among ex-smokers, and whether this relationship varied by length of smoking abstinence. Method: The study included 1064 ex-smokers (18+ years) from Canada (n = 340), US (n = 314), England (n = 261), and Australia (n = 149) who participated in the 2018 and 2020 International Tobacco Control Four Country Smoking and Vaping Survey, and we conducted analyses using multivariable logistic regression. We assessed alcohol consumption in 2018 using AUDIT-C and coded as never/low, moderate or heavy level and used alcohol consumption to predict smoking status in 2020. Results: Overall 26 % and 21 % of ex-smokers consumed alcohol at a moderate and heavy level, respectively. Compared to never/low alcohol consumption, risk of smoking relapse among those who consumed alcohol at a moderate level was significantly lower within the first year of abstinence (OR = 0.34, 95 % CI = 0.14-0.81, p = 0.015) but higher thereafter (OR = 2.44, 95 % CI = 1.13-5.23, p = 0.023). The pattern of results was similar for those who consumed alcohol at a heavy level. Conclusions: Overall, baseline alcohol consumption of ex-smokers did not predict their smoking relapse risk. As expected, risk differed by smoking abstinence duration. However, the pattern was unexpected among the shortterm quitters as the subgroup who drank moderately/heavily had lower relapse risk than their counterparts who never drink or at low level, underscoring the need to replicate this unexpected finding.