ABSTRACT: INTRODUCTION:Far too few smokers receive recommended interventions at their healthcare visits, highlighting the importance of identifying effective, low-cost smoking interventions that can be readily delivered. Self-help interventions (e.g., written materials) would meet this need, but they have shown low efficacy. The purpose of this RCT was to determine the efficacy of a self-help intervention with increased duration and intensity. DESIGN:Randomized parallel trial design involving enrollment between April 2010 and August 2011 with follow-up data for 24 months. SETTING/PARTICIPANTS:U.S. national sample of daily smokers (N=1,874). INTERVENTION:Participants were randomized to one of three arms of a parallel trial design: Traditional Self-Help (TSH, n=638), Standard Repeated Mailings (SRM, n=614), or Intensive Repeated Mailings (IRM, n=622). TSH received an existing self-help booklet for quitting smoking. SRM received eight different cessation booklets mailed over a 12-month period. IRM received monthly mailings of ten booklets and additional material designed to enhance social support over 18 months. MAIN OUTCOME MEASURES:The primary outcome was 7-day point-prevalence abstinence collected at 6, 12, 18, and 24 months. RESULTS:Data were analyzed between 2013 and 2015. A dose-response effect was found across all four follow-up points. For example, by 24 months, IRM produced the highest abstinence rate (30.0%), followed by SRM (24.4%) and TSH (18.9%). The difference in 24-month abstinence rates between IRM and TSH was 11.0% (95% CI=5.7%, 16.3%). Cost analyses indicated that, compared with TSH, the incremental cost per quitter who received SRM and IRM was $560 and $361, respectively. CONCLUSIONS:Self-help interventions with increased intensity and duration resulted in significantly improved abstinence rates that extended 6 months beyond the end of the intervention. Despite the greater intensity, the interventions were highly cost effective, suggesting that widespread dissemination in healthcare settings could greatly enhance quitting. TRIAL REGISTRATION:This study is registered at www.clinicaltrials.gov NCT01352195.
