Armstrong 1990 (Peer).

Methods	Country: Australia Site: 45 primary schools in Nedlands, Western Australia Focus: smoking prevention Design: Cluster RCT (Group 1: never smoking prevention cohort)
Participants	Baseline: (1981) 2366 Age: 7th grade (modal age 12 years) Gender: 49% F Ethnicity: Not stated Baseline smoking data: Smoking prevalence 24 ‐ 37%
Interventions	Category: Social influences vs control Programme deliverer: Teachers and peers ("all leaders received appropriate previous training") Intervention: (6m duration) Peer‐led (selected by class), teacher facilitated; 5 sessions. Intervention based on Minnesota model. Components: estimating smokers in age group; negative consequences; why children smoke; physiological effects; information on % of smokers; listed situations where pressure to smoke; practised refusal techniques; students presented arguments for nonsmokers' rights; developed counter‐arguments to smokers' reasons for smoking; role of the family; advertising techniques; essay on reasons for remaining nonsmokers; public commitment Teacher‐led same programme Control: No planned intervention
Outcomes	Nonsmoking in previous 12m (not smoked a single cigarette, not even a few puffs). Saliva samples collected but not analysed. Follow‐up: 12m, 24m, 7 yrs from end of programme.
Notes	Quality of intervention delivery: No process analysis of delivery of the intervention; the authors state "all leaders received appropriate previous training". Statistical quality: Was a power computation performed? No Was an intention‐to‐treat analysis performed? No Was a correction for clustering made? The data on schools were erased after 1yr, so that ICCs could not be computed, and the data were not corrected for the effects of clustering [the authors state: "Given the large number of original classes and the subsequent mixing of students that is described above, it is likely that any biases which arose in estimates of their effects or their precision because of the analysis of individuals rather than classes would be small". Were appropriate statistical methods used? Comparison of the proportions of students in the 3 groups who took up smoking was by Pearson's Χ2 (two‐sided); effects of other variables controlled in separate LRs (using EGRET) for boys and girls, and for each year of follow‐up, using only children present at baseline and both follow‐ups. Once the final models were chosen, the parameters were re‐estimated with an added risk model.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"Each school was assigned at random to one of three interventional groups: control group (no planned intervention); peer‐led programme; and teacher‐led programme". No comment on method of randomisation. Clusters: Schools Cluster constraint: Stratified by class size and location Baseline comparability: No differences between groups at baseline, smoking prevalence higher for boys than girls
Allocation concealment (selection bias)	Unclear risk	No statement
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	"At the time of the survey, the children, their teachers and those who conducted the survey did not know the interventional group to which the class was assigned"
Incomplete outcome data (attrition bias) All outcomes	High risk	"Eighty‐two per cent and 64% of students were traced and re‐surveyed in the first and second follow‐up studies respectively". [after 1 and 2 years] "Seven years after the first survey of 2,366 Year 7 students in 1981 68% were traced through public records [Driver's Licences, electoral commissions and registries of births marriages and deaths]; 53 per cent of these responded to a new survey concerning smoking". [i.e. 37% of original sample] No differential attrition by treatment group at 12m follow up. Saliva samples were collected but not analysed. At the 7 yr follow up, non‐response was associated (P < .05) with being male, being in the control group, thinking most adults smoked, and mother and brother smoked.
Selective reporting (reporting bias)	Low risk	Abstract states: "How effective are peer‐led programmes in preventing the uptake of smoking by children?" This outcome is fully reported.