Design of a school-based randomized trial to reduce smoking among 13 to 15-year olds, the X:IT study

Abstract

BackgroundAdolescent smoking is still highly prevalent in Denmark. One in four 13-year olds indicates that they have tried to smoke, and one in four 15-year olds answer that they smoke regularly. Smoking is more prevalent in socioeconomically disadvantaged populations in Denmark as well as in most Western countries. Previous school-based programs to prevent smoking have shown contrasting results internationally. In Denmark, previous programs have shown limited or no effect. This indicates a need for developing a well-designed, comprehensive, and multi-component intervention aimed at Danish schools with careful implementation and thorough evaluation.This paper describes X:IT, a study including 1) the development of a 3-year school-based multi-component intervention and 2) the randomized trial investigating the effect of the intervention. The study aims at reducing the prevalence of smoking among 13 to 15-year olds by 25%.Methods/DesignThe X:IT study is based on the Theory of Triadic Influences. The theory organizes factors influencing adolescent smoking into three streams: cultural environment, social situation, and personal factors. We added a fourth stream, the community aspects. The X:IT program comprises three main components: 1) smoke-free school premises, 2) parental involvement including smoke-free dialogues and smoke-free contracts between students and parents, and 3) a curricular component. The study encompasses process- and effect-evaluations as well as health economic analyses. Ninety-four schools in 17 municipalities were randomly allocated to the intervention (51 schools) or control (43 schools) group. At baseline in September 2010, 4,468 year 7 students were eligible of which 4,167 answered the baseline questionnaire (response rate = 93.3%).DiscussionThe X:IT study is a large, randomized controlled trial evaluating the effect of an intervention, based on components proven to be efficient in other Nordic settings. The X:IT study directs students, their parents, and smoking prevention policies at the schools. These elements have proven to be effective tools in preventing smoking among adolescents. Program implementation is thoroughly evaluated to be able to add to the current knowledge of the importance of implementation. X:IT creates the basis for thorough effect and process evaluation, focusing on various social groups.Trial registrationCurrent Controlled Trials ISRCTN77415416.

Association of School Characteristics and Implementation in the X:IT Study—A School‐Randomized Smoking Prevention Program

“…The evaluation was designed as a cluster‐randomized controlled trial with schools from all over Denmark. The program consisted of 3 main intervention components: smoke‐free school grounds; smoke‐free curriculum; and parental involvement comprising smoke‐free contracts and dialogues …”

“…Detailed information on study design and population has previously been published . In the evaluation of the X:IT study, there were 51 intervention and 43 control schools.…”

High impact of implementation on school-based smoking prevention: the X:IT study—a cluster-randomized smoking prevention trial

“…X:IT consists of three main intervention components: (1) smoke-free school grounds, (2) smoke-free curriculum, and (3) parental involvement comprising smoke-free contracts and dialogues [ 35 ].…”

The Hi Five study: design of a school-based randomized trial to reduce infections and improve hygiene and well-being among 6–15 year olds in Denmark

“…All 10 years are mandatory. The Danish children start school the year they turn 6 [ 39 ]. Children who start together in the same class at year 0 will often belong to the same class/group of children throughout at least the first 7 years if not all ten years of schooling.…”