There were 662 participants eligible for the gum adherence analysis, 242 (36.6%) of whom were categorized as adherent to recommended pieces of nicotine (or placebo) gum. The baseline characteristics by gum adherence group are presented in Table . Univariate predictors of adherence to gum use included being unemployed, higher income, higher BMI, more quit attempts in the past year, higher baseline exhaled CO level, higher nicotine dependence, and higher perceived stress.
Of the 755 participants included in the counseling adherence analysis, 542 (71.8%) were categorized as adherent to counseling. The baseline characteristics of participants by counseling adherence status are presented in Table . Univariate predictors of adherence to counseling were older age, being a high school graduate, and longer smoking history.
Baseline Characteristics by Counseling (HE/MI) Adherence Groups
Results of the multiple logistic regression analysis of predictors of adherence to gum use are shown in Table . This model included variables from Table that had p-values <0.1 plus counseling adherence status. Four variables emerged as independent predictors of gum adherence, including having a higher body mass index, making more quit attempts in the past year, having a higher baseline exhaled CO, and higher perceived stress score.
Full Regression Model of Baseline Predictors of Adherence to Nicotine Gum
Results of a multiple logistic regression to predict adherence to counseling are shown in Table . This model included variables from Table that had p-values <0.1 plus gum adherence status. Only one variable, being a high school graduate, significantly increased the odds of adherence to counseling.
Full Regression Model of Baseline Predictors of Adherence to Counseling
Figure shows the cotinine-verified abstinence rates for the four study groups. As previously reported12
, the primary outcome of the parent study was that the verified abstinent rate at week 26 for 2 mg nicotine gum was no better than for placebo (14.2% versus 11.1%, P
0.232). However, a counseling effect was observed, with health education (HE) performing significantly better than motivation interviewing (MI) (16.7% versus 8.5%, P
0.001). In the current study, adherence rates to nicotine gum (Fig. ) were not significantly different among the four study groups (global p
0.53). However, as shown in Figure , there were significant differences in counseling adherence rates among the four study groups, with the placebo + MI group (62.4%) having the lowest rate, while the NRT + HE group (78.8%) had the highest adherence rate (global p
0.01). The verified quit rates at week 26 for the counseling adherent and non-adherent groups were 16.1% and 3.76%, respectively (P
0.0001). Unexpectedly, the verified quit rates at week 26 for the gum adherent and non-adherent groups were 9.5% and 16.7%, respectively.
Verified quit rates by four treatment groups.
Adherence to nicotine gum by treatment groups.
Adherence to counseling by treatment groups.
We also performed a multiple logistic regression model to determine predictors of cotinine-verified week 26 abstinence rates (Table ). Consistent with the univariate analysis above, being adherent to nicotine gum significantly reduced the odds of smoking cessation (OR
0.28 to 0.87). On the other hand, adherence to counseling dramatically increased the likelihood of smoking cessation (OR
1.36 to 8.08). When supplemental analyses were performed that treated gum adherence (parameter estimate
0.001) and counseling adherence (parameter estimate
0.001) as continuous variables, the relationship between gum adherence and cessation as well as between counseling adherence and cessation were essentially unchanged. Other baseline predictors of smoking cessation were consistent with those previously reported41
, including higher body mass index and older age, female gender, and higher baseline exhaled carbon monoxide reduced the odds of quitting.
Full Regression Model of Baseline Predictors of Cotinine-verified Quitting at Week 26