Lopez 2004.

Methods	Cohort study Baseline: Date unknown (prior to July 2001) Follow‐up: 6, 12 and 18 months later Site: Asturias, Spain Research Question: Investigate possible associations between billboard advertising from cigarettes and smoking behaviour Analysis: Logistic regression; Bivariate analysis to measure association between number of advertisements recognized and smoking status; Pearsons's Chi test of significance Controlled for age, gender, SES, attitude, social influence, and self‐efficacy.
Participants	At baseline, 3,664 children aged 13‐14; 3,089 at 6 months; 2,395 at 12 months; and 2,356 at 18 months. At 18 months, attrition was 35.7%. Participants were from 69 schools, located in municipalities of more than 50,000 in Asturias, Spain. Survey method: Self‐report survey administered in groups and in class
Interventions	Advertisement awareness was measured at baseline only. Selection criteria for choosing cigarette advertisements were: (1) to have been on billboards within a radius of 500m of the schools at some time during the 3 months preceding the study, and (2) to be focused on young people (iconic and/or textual message). Experts selected, by consensus, the three advertisements with messages that were most focused on young people. Slides of these advertisements, with brand names covered, were shown to students. Students were asked to write the brand name, if recognized. An advertisement was assumed to be recognized when the brand was identified. Range of responses was 0, 1, 2, or 3 brand names identified and children were assigned to a group according to their reply, and remained in that group until the end of the study.
Outcomes	Regular smoking was measured at baseline, 6, 12 and 18 months. Two categories were used, Non‐Smoker ( defined as never smoked or smokes less than once per week, or ex‐smoker) and Smoker (defined as having at least one cigarette per week on a regular basis).
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