Background: Adult smoking usually has its roots in adolescence. If individuals do not take up smoking during this period it is unlikely that they ever will. Further, once smoking becomes established, cessation is challenging; the probability of subsequently quitting is inversely proportional to the age of initiation. One novel approach to reducing the prevalence of youth smoking is the use of incentives.
Objectives: To determine whether incentives prevent children and adolescents from starting to smoke. We also attempted to assess the dose-response of incentives, the costs of incentive programmes, whether incentives are more or less effective in combination with other interventions to prevent smoking initiation and any unintended consequences arising from the use of incentives.
Search methods: We searched the Cochrane Tobacco Addiction Group Specialized Register, with additional searches of MEDLINE, EMBASE, CINAHL, CSA databases and PsycINFO for terms relating to incentives, in combination with terms for smoking and tobacco use, and children and adolescents. The most recent searches were in May 2012.
Selection criteria: We considered randomized controlled trials allocating children and adolescents (aged 5 to 18 years) as individuals, groups or communities to intervention or control conditions, where the intervention included an incentive aimed at preventing smoking uptake. We also considered controlled trials with baseline measures and post-intervention outcomes.
Data collection and analysis: Data were extracted by two authors and assessed independently. The primary outcome was the smoking status of children or adolescents at follow-up who reported no smoking at baseline. We required a minimum follow-up of six months from baseline and assessed each included study for risk of bias. We used the most rigorous definition of abstinence in each trial; we did not require biochemical validation of self-reported tobacco use for study inclusion. Where possible we combined eligible studies to calculate pooled estimates at the longest follow-up using the Mantel-Haenszel fixed-effect method, grouping studies by study design.
Main results: We identified seven controlled studies that met our inclusion criteria, including participants with an age range of 11 to 14 years. Of the seven trials identified, only five had analysable data relevant for this review and contributed to the meta-analysis (6362 participants in total who were non-smokers at baseline; 3466 in intervention and 2896 in control). All bar one of the studies was a trial of the so-called Smokefree Class Competition (SFC), which has been widely implemented throughout Europe. In this competition, classes with youth generally between the ages of 11 to 14 years commit to being smoke free for a six month period. They report regularly on their smoking status; if 90% or more of the class is non-smoking at the end of the six months, the class goes into a competition to win prizes. The one study that was not a trial of the SFC was a controlled trial in which schools in two communities were assigned to the intervention, with schools in a third community acting as controls. Students in the intervention community with lower smoking rates at the end of the project (one school year) received rewards.
Only one study of the SFC competition, a non-randomized controlled trial, reported a significant effect of the competition on the prevention of smoking at the longest follow-up. However, this study had a risk of multiple biases, and when we calculated the adjusted RR we no longer detected a statistically significant difference. The pooled RR for the more robust RCTs (3 studies, n = 3056 participants) suggests that, from the available data, there is no statistically significant effect of incentives to prevent smoking initiation among children and adolescents in the long term (RR 1.00, 95% CI 0.84 to 1.19). Pooled results from non-randomized trials also did not detect a significant effect, and we were unable to extract data on our outcome of interest for the one trial that did not study the SFC. There is little robust evidence to suggest that unintended consequences (such as youth making false claims about their smoking status and bullying of smoking students) are consistently associated with such interventions, although this has not been the focus of much research. There was insufficient information to assess the dose-response relationship or to report costs.
Authors' conclusions: To date, incentive programmes have not been shown to prevent smoking initiation among youth, although there are relatively few published studies and these are of variable quality. Trials included in this meta-analysis were all studies of the SFC competition, which distributed small to moderately sized prizes to whole classes, usually through a lottery system.
Future studies might investigate the efficacy of incentives given to individual participants to prevent smoking uptake. Future research should consider the efficacy of incentives on smoking initiation, as well as progression of smoking, evaluate these in varying populations from different socioeconomic and ethnic backgrounds, and describe the intervention components in detail.