Bronson 1989.

Methods	Study design: Randomized controlled trial Setting: internal medicine practice, USA Recruitment: attenders for periodic health examinations
Participants	155 smokers 38% men, av. age 42, av. cpd 25
Interventions	Therapist: smoking cessation counsellor 1. 2 x 20‐min counselling sessions during a periodic health examination (benefits of quitting, assessment of motivation, quit plan, high risk/problem solving) 2. Control: completed smoking behaviour questionnaire
Outcomes	Abstinence at 18 m (sustained from 6 ‐ 18 m) Validation: no biochemical validation at 18 m, limited sample for saliva cotinine at 6 m
Notes	18 m data reported in Secker‐Walker 1990
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomized, method not described
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding of outcome assessment (detection bias) All outcomes	High risk	Physicians carrying out health examinations were blind to group assignment and would have given similar advice to all participants Long‐term abstinence not validated
Incomplete outcome data (attrition bias) All outcomes	Low risk	20 (13%) not contacted at 6 m and 18 m, included in ITT analysis