Initial evaluation of a real-world Internet smoking cessation system.

To significantly reduce smoking prevalence, treatments must balance reach, efficacy, and cost. The Internet can reach millions of smokers cost-effectively. Many cessation Web sites exist, but few have been evaluated. As a result, the potential impact of the Internet on smoking prevalence remains unknown. The present study reports the results, challenges, and limitations of a preliminary, large-scale evaluation of a broadly disseminated smoking cessation Web site used worldwide (QuitNet). Consecutive registrants (N=1,501) were surveyed 3 months after they registered on the Web site to assess 7-day point prevalence abstinence. Results must be interpreted cautiously because this is an uncontrolled study with a 25.6% response rate. Approximately 30% of those surveyed indicated they had already quit smoking at registration. Excluding these participants, an intention-to-treat analysis yielded 7% point prevalence abstinence (for the responders only, abstinence was 30%). A range of plausible cessation outcomes (9.8%-13.1%) among various subgroups is presented to illustrate the strengths and limitations of conducting Web-based evaluations, and the tensions between clinical and dissemination research methods. Process-to-outcome analyses indicated that sustained use of QuitNet, especially the use of social support, was associated with more than three times greater point prevalence abstinence and more than four times greater continuous abstinence. Despite its limitations, the present study provides useful information about the potential efficacy, challenging design and methodological issues, process-to-outcome mechanisms of action, and potential public health impact of Internet-based behavior change programs for smoking cessation.