Effectiveness of Peer-Support Interventions for Smoking Cessation: A Systematic Review and Meta-analysis

Introduction Peer support has been recommended to promote smoking cessation, but results from prior meta-analyses have not established its efficacy. We conducted a systematic review and meta-analysis to assess current evidence and identify potential modifiers of efficacy. Methods Randomized controlled trials of peer-support interventions with a smoking cessation outcome were identified in January 2022 from PubMed and references listed in identified studies. The meta-analysis outcome measure was mean risk ratio (RR, 95% confidence interval [CI]) for abstinence at the longest follow-up timepoint between 3 and 9 months from baseline. Potential modifiers tested were peer smoking status (former, current, or unknown), follow-up timepoint, abstinence measure, and cumulative engagement time between peers and smokers ("dose"). Studies were assessed for risk of bias and certainty of evidence. Results We identified 16 trials, which varied in abstinence effect size (RR 0.61-3.07), sample size (23-2121), dose (41-207 minutes), and follow-up timepoint (<1-15 months). Across 15 trials with follow-up between 3 and 9 months (N = 8573 participants; 4565 intervention, 4008 control), the pooled Mantel-Haenszel RR was 1.34 (95% CI: 1.11-1.62). Effect sizes were greatest among interventions with formerly smoking peers (RR 1.43, 95% CI 1.17-1.74; five trials). We found positive effects for follow-up timepoints >= 3 months but no effect of intervention dose. The overall quality of evidence was deemed "very low." Conclusions Peer-support interventions increased smoking abstinence. There remains a lack of consensus about how to define a peer. Intervention features such as peer smoking status appear to have explanatory power. Additional high-quality and more comparable trials are needed. Implications This study reviewed the latest evidence from randomized controlled trials and found that peer-support interventions enhance smoking cessation. Efficacy varies with key intervention features such as peer smoking status and follow-up timepoint, which may be used to facilitate development of more effective peer-support interventions. Future trials and reviews would benefit from careful consideration and clear reporting of peer smoking status, length of follow-up, abstinence measures, and intervention dose.