Klesges 1999

Methods	Setting: Air Force, USA Recruitment: recruits undergoing basic military training (BMT)
Participants	18,010 recruits, 29% regular smokers before enforced abstinence during training. 28% female, average age 20
Interventions	1. Single 50‐min intervention during final week of training, 50/group, including non‐smokers. Discussed health effects, costs, social impact, role‐play 2. Control: general health video All participants exposed to 6 weeks smoking ban and shown 2 videos to preview primary intervention
Outcomes	Abstinence at 12 months (not defined) Validation: none Relapse amongst baseline ex‐smokers and initiation amongst non‐smokers also reported
Notes	Results not displayed graphically because denominators not explicit. No significant overall benefit. ICC small (0.004 for smokers)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Cluster‐randomised by training flight. 75% assigned to intervention, method of sequence generation not specified
Allocation concealment (selection bias)	Low risk	Not specified, but training flight allocation was independent of this trial, so potential for bias small
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No blinding reported, control knowledge of intervention unclear, personnel knowledge of participant assignment not reported
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Although no biochemical validation used, intervention was of low intensity with limited face‐to‐face contact, sample size was large, follow‐up rate was high and self‐report was via survey. Risk of differential misreport was low
Incomplete outcome data (attrition bias) All outcomes	Low risk	96% of available smokers reached