Study protocol for a cluster randomised controlled trial testing the effectiveness of the 'High schools High on life' intervention on reducing excessive drinking in Danish high schools

The Danish National Youth Study 2019: study design and participant characteristics

AIM

To present the study design, study population and questionnaire content of the Danish National Youth Study 2019, and to describe the differences between participants and non-participants regarding demographic and socioeconomic characteristics.

METHOD

The Danish National Youth Study 2019 is a nationwide web-survey among high school students in Denmark. Data was collected from January to April 2019 through a self-administered questionnaire in the classroom. The questionnaire included 120 questions on, for example, physical and mental health, health behaviour and well-being. Data collection took place at 50 general high schools, 32 preparatory high schools, 15 commercial high school and 19 technical high schools.

RESULTS

A total of 29,086 students participated (20,287 general high school students, 2,113 preparatory higher school students, 4027 commercial high school students and 2659 technical high school students) corresponding to 66% of the students in the 88 participating schools (31% of invited schools). Among students, 55% were female and the mean age was 17.8 years. Participants were more likely to be female, to be younger, to be of Danish origin, and have family disposable income in the highest quartile compared to non-participants.

CONCLUSIONS

The Danish National Youth Study 2019 contributes to knowledge on high school students' health, health behaviour and well-being that can support health planning and prioritizing, through identification of specific risk groups at both local and national level. The study also offers great opportunities for future research as it provides possibility of linkage to various Danish national registers.

'High schools High on life': Development of an Intervention to Reduce Excessive Drinking in Danish High Schools

Background: Clear documentation of the understanding of the problem, process of development, and content of interventions is essential to enable other researchers to understand why interventions succeed or fail and to enable researcher to build on previous evidence and replicate and adapt findings in other contexts. In this paper we describe the rationale, intervention development, and final design of the 'High schools High on life' intervention; a high school-based, multi-component intervention to reduce excessive drinking among Danish high school students. Methods: The development of the intervention 'High schools High on life' was guided by the planning steps of the Intervention Mapping protocol (IM) in combination with the behavior change wheel and the behavior change techniques, theory, evidence, practice, and new empirical studies of contextual factors in the Danish high school setting. Results: The development process resulted in a multi-component intervention with the following intervention elements: a school environmental component targeting school alcohol policies and norms, a school educational component addressing students' social norms around alcohol, and a parental component encouraging parent-child communication around alcohol. Discussion: Not all steps of IM were followed rigidly. However, IM proved useful as a planning tool in combination with the behavior change wheel and the behavior change techniques, as it provided a systematic approach to the intervention development process. IM forced the research group to be explicit about decisions and choices throughout the planning process. The transparency of the developmental process and theoretical, empirical and practical/contextual foundation of the 'High schools High on life' intervention may enable future intervention studies to build on our findings and accumulate knowledge to reduce excessive drinking among young people. Trial registration: The trial was registered at clinicaltrials.gov (Trial registration number NCT03906500) prior to randomization.