Do predictors of smoking relapse change as a function of duration of abstinence? Findings from the United States, Canada, United Kingdom and Australia

AIMS To estimate predictors of time to smoking relapse and test if prediction varied by quit duration. DESIGN Longitudinal cohort data from the International Tobacco Control Four-Country survey with annual follow up collected between 2002 and 2015. SETTING Canada, United States, United Kingdom and Australia. PARTICIPANTS A total of 9171 eligible adult smokers who had made at least one quit attempt during the study period. MEASUREMENTS Time to relapse was the main outcome. Predictor variables included pre-quit baseline measures of nicotine dependence, smoking and quitting-related motivations, quitting capacity and social influence, and also two post-quit measures, use of stop-smoking medications and quit duration (1-7 days, 8-14 days, 15-31 days, 1-3 months, 3-6 months, 6-12 months, 1-2 years and 2+ years), along with socio-demographics. FINDINGS All factors were predictive of relapse within the first 6 months of quitting but only wanting to quit, quit intentions and number of friends who smoke were still predictive of relapse in the 6-12-month period of quitting [hazard ratios (HR) = 1.20, P < 0.05; 1.13, P < 0.05; and 1.21, P