Early cigarette smoking reduction and longer-term smoking abstinence in a randomized placebo-controlled e-cigarette trial among people who smoke with no plans to quit.

INTRODUCTION: Evidence from nicotine replacement therapy (NRT) trials for smoking reduction suggests that early reductions in cigarette consumption are associated with long-term smoking abstinence among individuals not initially planning to quit. Whether similar associations exist in smoking reduction trials using electronic cigarettes (e-cigarettes) remains unclear. METHODS: We conducted an exploratory analysis of a placebo-controlled smoking reduction trial among adults (N=520) who smoked ≥10 cigarettes per day (CPD) and were interested in reducing, but not quitting. Participants were randomized to e-cigarettes (0, 8, or 36 mg/mL nicotine) or a cigarette substitute. Early smoking reduction was defined as a ≥50% reduction in CPD or exhaled carbon monoxide (CO) at 2 weeks relative to baseline. The primary outcome was biochemically verified 7-day point prevalence abstinence at 24 weeks. Multivariable logistic regression models were used to examine the association adjusting for study site, randomized group, age and Penn State Cigarette Dependence Index. RESULTS: At 2 weeks, 72/445 participants (16.2%) achieved a ≥50% reduction in CPD and 77/446 (17.3%) achieved a ≥50% reduction in CO. Participants who achieved a ≥50% reduction in CPD at 2 weeks had significantly higher odds of smoking abstinence at 24 weeks compared with those who did not reduce (AOR=6.5, 95% CI: 2.3-18.7). Similarly, a ≥50% reduction in CO at 2 weeks was associated with increased odds of abstinence at 24 weeks (AOR=5.8, 95% CI: 2.2-15.9). CONCLUSION: Achieving ≥50% smoking reduction within the first two weeks was strongly associated with long-term smoking abstinence in a smoking reduction trial using e-cigarettes.