3.1. Internal validity/compliance
Almost all (90%) of the smokers in the gradual condition were assigned 4 mg lozenge because they smoked within 30 minutes of arising. Prior to the quit date, 93% of smokers in the gradual condition used at least one nicotine lozenge and 86% used lozenges for 1 week or more. They used a median of 83% of days and used an average of 18.6 mg/day (i.e. 4–5 lozenges) on the days they used. In the week after the quit attempt, the mean number of days NRT was used was 6.5 in the gradual, 6.2 in the abrupt condition and 6.0 in the minimal treatment (F(2,419) = 2.01, p = 0.14). The incidence of AEs rated severe was small and similar across gradual, abrupt, and minimal treatment conditions (3% vs. 5% vs. 3%), and the incidence of discontinuation due to AEs was < 1% for all three groups. Most participants completed ≥ 4/5 treatment calls in the gradual (79%) and abrupt (78%) conditions or completed 2/2 calls in the minimal treatment (83%) condition.
The mean decrease in CPD between study entry and the week prior to the quit date among the subset of participants with no missing data was 54% (13 CPD ) in the gradual vs. 1% (0.3 CPD) in the abrupt and 5% (1 CPD) in the minimal treatment condition. The decrease in CO was 21% (6 ppm) in the gradual vs. 0% (0 ppm) in the abrupt condition. As expected, the mean time until the designated quit date was greater in the gradual than in the abrupt or minimal treatment conditions (27 vs. 15 vs. 15 days, F(2,718) = 358.7, p < .001).
The three conditions did not differ statistically on any measure of abstinence at 6-month follow-up (); however, the gradual condition had a consistent, non-significant trend for lower abstinence rates. Because the incidence of 6-month contacts and of CO sampling differed somewhat across groups, we re-ran the analyses in using only those contacted at 6 months. Although the quit rates were higher, the odds ratio across the groups were very similar to the results in .
Abstinence outcomes at 6 month follow-upa
Smokers in the gradual condition were less likely to make a quit attempt, defined as ≥ 1 day of not smoking, than those in the abrupt and minimal treatment conditions (48% vs. 64% vs. 60%, χ2(2) = 15.9, p < .001). In a survival analysis of lapses in the first 6 weeks (the time period in which we collected daily data), the time to lapse was non-significantly longer for abrupt than gradual conditions (proportional hazard ratio (HR) = 1.2, χ2(1) = 3.35, p=.07), and for abrupt vs. minimal treatment conditions (HR= 1.2, χ2(1) = 2.52, p = .11), but did not differ between gradual and minimal treatment conditions (HR= 1.0, χ2(1) = 0.00, p=0.96) ().
Figure 3 Survival curve of time-to-self-reported first lapse among quit attempters. For those who did not quit or relapsed on the first day of abstinence, we assigned a value of zero. Due to the timing of calls, we sometimes did not inquire about smoking on every (more ...)
3.3. Effects of Gradual Reduction on Self-Efficacy, Dependence and Regularity of Smoking
We measured whether gradual cessation prior to the quit date had the anticipated effects on self-efficacy, dependence and regularity of smoking by examining the results of the baseline and pre-quit questionnaires. The outcomes of these results must be interpreted cautiously for two reasons. First, we were not able to verify that the pre-quit questionnaire was completed immediately prior to cessation. Secondly, the rate of completion of both the baseline and pre-quit surveys differed across conditions, with 57% completion in the gradual, 82% in the abrupt, and 70% in the minimal treatment condition, (χ2(2) = 44.3, p < .001); thus, the outcomes reported below are based on this self-selected subsample.
As anticipated, participants in the gradual condition increased self-efficacy more (mean score at baseline = 18 vs. at pre-quit = 23) than in the other two conditions (18 at pre-cessation to 19 at pre-quit for each, F(2,502) = 45.67, p <.0001). A similar effect occurred with the 5-point confidence in quitting scale (F(2,510) = 2.97, p=.05) and the 5-point perceived difficulty in quitting scale (F(2,504) = 24.63, p < .0001). Participants in the gradual condition also decreased dependence; i.e., increased time to first cigarette (15 to 28 minutes), but participants in the other two conditions did not (F(2,509) = 21.29p <.0001). Similar outcomes occurred with the dependence measures of FTND (F(2,487) = 12.15, p<.0001) and self-rated addiction (F(2,512) = 62.13, p < .0001). Participants in the gradual condition decreased the regularity of smoking (from 6.9 to 5.3 on the 1–10 scale) indicating smoking became more disrupted, but the regularity of smoking did not change in participants in the other two conditions (F(2,507) = 30.26, p < .0001). Craving decreased in the gradual condition (4.5 to 4.0 on 1–5 scale) from baseline to pre-quit, but did not do so in the other two conditions (4.5 to 4.4, F(2,508) = 9.16, p <.0001).
Within the gradual condition, we examined predictors of time-to-lapse via a series of bivariate analyses. The following were not predictors of survival time in the first 6 weeks: greater reductions in CPD, time-to-first cigarette, confidence in quitting, motivation to quit, self-efficacy, craving, dependence, and regularity of smoking. However, for every extra week between study entry and the quit day within the gradual condition, the probability of lapsing increased by 19% (HR = 1.19; χ2(1) = 4.80, p =. 03). Within the gradual condition, the amount of use of NRT was not related to survival time.
3.4. Possible moderators
We tested whether the following baseline characteristics interacted with the effect of gradual vs. abrupt treatment on survival time: age, sex, race, CPD, FTND, self-rated addiction, confidence in ability to quit, intention to quit in the next month, confidence could quit gradually, confidence could quit abruptly, and their ratio, desire to quit gradually vs. abruptly, self-efficacy, and regularity of smoking. Among smokers who rated their dependence as low on the visual analog scale at study onset, the abrupt condition had a better outcome than the gradual condition (i.e., had a longer time to lapse); however, among smokers who rated themselves as highly dependent, the abrupt condition did not have a better outcome than the gradual condition. (χ2(1) = 3.91, p = .05). A similar, but non-significant, interaction occurred with the other two dependence measures of FTND and CPD. Among smokers with high self-efficacy, the abrupt condition out-performed the gradual condition but among smokers with low self-efficacy, the abrupt condition did not out-perform the gradual condition (χ2(1) = 4.98, p = .03). A similar, but non-significant, interaction occurred with self-rated confidence in quitting. Surprisingly, relative preference for gradual vs. abrupt cessation did not predict response to treatment. Also, those who did not return the pre-quit questionnaire were more likely to relapse (HR = 1.23, 1.01–1.49) but this effect did not interact with experimental conditions. None of the above moderators influenced point prevalence and prolonged outcomes.