Background
Partial adherence in Internet smoking cessation interventions presents treatment and evaluation challenges. Increasing
adherence may improve outcomes.
Purpose
To present smoking outcomes from an Internet randomized trial of two strategies to encourage adherence to tobacco
dependence treatment components (i.e., skills training, social support, medication): 1) a social network (SN) strategy to
integrate smokers into an online community, and 2) free nicotine replacement therapy (NRT). In addition to intent-to-treat
analyses, we used novel statistical methods to distinguish the impact of treatment assignment from treatment
utilization.
Methods
N=5,290 current smokers on a cessation website (WEB) were randomized to WEB, WEB+SN, WEB+NRT,
or WEB+SN+NRT. The main outcome was 30-day point prevalence abstinence at 3 and 9 months post-randomization.
Adherence measures included website metrics of skills training and community use, and self-reported medication use. Inverse
Probability of Retention Weighting and Inverse Probability of Treatment Weighting jointly addressed dropout and treatment
selection. Propensity weights were used to calculate Average Treatment effects on the Treated.
Results
Treatment assignment analyses showed no effects on abstinence for either adherence strategy. Treatment
utilization analyses revealed that joint community and medication use yielded large percentage point
increases in 3-month abstinence rates over skills training alone across arms: WEB=20.6 (95% CI=10.8,
30.4), WEB+SN=19.2 (95% CI=11.1, 27.3), WEB+NRT=13.1 (95%
CI=4.1, 22.0), and WEB+SN+NRT=20.0 (95% CI=12.2, 27.7). Abstinence rates among
participants that used all treatment components were 25.7%-32.2%.
Conclusions
Novel propensity weighting approaches can serve as a model for establishing efficacy of Internet interventions and
yield important insights about mechanisms.
Clinical Trials.gov
NCT01544153