AIMS: It is not known whether the machine-smoked nicotine yield of usual brand of cigarette smoked is associated with the chances of success of quit attempts. This study aimed to assess this association. DESIGN: Prospective study. SETTING: Republic of Korea. PARTICIPANTS: A total of 16 808 male smokers registered for the Quitline between 7 April 2006 and 31 December 2013. Of these, 13 176 participants who were > 19 years of age and provided data on their demographic characteristics, smoking-related behaviors, nicotine dependence, tobacco brands used and self-efficacy were included in this study. MEASUREMENTS: Machine-smoked nicotine yield was based on information provided by tobacco companies on cigarette packages that smokers reported as their usual brand. Ultra-low nicotine yield was defined as ≤ 0.1 mg machine-smoked nicotine yield per cigarette, whereas higher nicotine yield was defined as > 0.1 mg machine-smoked nicotine yield. Participant personal information and self-reported continuous abstinence at 1-month, 6-month and 1-year follow-up were recorded in electronic databases. FINDINGS: Continuous abstinence rates in the ultra-low nicotine yield versus higher nicotine yield groups were, respectively, 40.7 versus 34.6% at 1 month [odds ratio (OR) = 1.22, 95% confidence interval (CI) = 1.12-1.33], 22.7 versus 18.8% at 6 months (OR = 1.20, 95% CI = 1.08-1.32) and 19.5 versus 16.6% (OR = 1.19, 95% CI = 1.10-1.29) at 1 year. The association between ultra-low nicotine yield cigarette smoking and successful quitting was stronger among the smokers with higher cigarette dependence. CONCLUSIONS: Male smokers who use the Korean Quitline are more likely to quit successfully if they smoke ultra-low nicotine yield cigarettes than if they smoke higher nicotine yield cigarettes.
