Exploring the "active ingredients" of an online smoking intervention: a randomized factorial trial

Abstract

Introduction: Research needs to systematically identify which components increase online intervention effectiveness (i.e., active ingredients). This study explores the effects of 4 potentially important design features in an Internet-based, population-level smoking intervention.

Methods: Smokers (n = 1,865) were recruited from a large health care organization, regardless of readiness to quit. Using a full factorial design, participants were randomized to 1 of the 2 levels of each experimental factor (message tone [prescriptive vs. motivational], navigation autonomy [dictated vs. not], e-mail reminders [yes vs. no], and receipt of personally tailored testimonials [yes vs. no]) and provided access to the online intervention. Primary outcomes were self-reported 7-day point-prevalent smoking abstinence and confirmed utilization of adjunct treatment (pharmacotherapy or phone counseling) available through the health plan at 1 year. Outcomes were also assessed at 2 and 6 months and were examined among all enrolled participants (intent-to-treat [ITT]) and all who viewed the intervention (modified ITT).

Results: At 1 year, 13.7% were abstinent and 26.0% utilized adjunct treatment. None of the contrasting factor levels differentially influenced abstinence or treatment utilization at 12 months. In the modified ITT sample, smokers receiving testimonials were less likely to use adjunct treatment at 6 months (odds ratio = 0.54, 95% confidence interval = 0.30-0.98, p = .04).

Conclusions: None of the design features enhanced treatment outcome. The negative effect observed for testimonials is provocative, but it should be viewed with caution. This study offers a model for future research testing the "active ingredients" of online interventions.

Figure 1.

Recruitment flow and allocation.^aTwo participants were not randomized due to a server error and were excluded from the analytic sample.^bHalf of participants were randomized to each level of each experimental factor using a two-level full factorial design, so all participants received an active intervention.^cIntent-to-treat analyses of main outcomes included complete case analyses with no missing data.^dAnalyses of treatment utilization were restricted to participants who were enrolled in the health plan for at least one day during the study period, excluding 27 people from the total sample for these analyses only.^eModified intent-to-treat analyses were restricted to persons who had viewed the intervention by each timepoint. Analyses of main outcomes included complete case analyses with no missing data.