In this study, preferences and attitudes towards breast cancer screening, invitation, and decision making among Danish women will be investigated. The aim is to gain knowledge about barriers for (informed) decision making in a Danish breast cancer screening context. The study will be conducted by sending out an online questionnaire to women aged 44-49 in Denmark. The questionnaire will be sent out using the official digital mail system, e-Boks, with an invitation, link, and login information to access the online questionnaire. The questionnaire will consist of background questions about the participants, questions related to the current information material and invitation to the Danish breast cancer screening program, and questions about decision making and informed choice. Women will be randomized to one of three questionnaires: 1) Questionnaire with "Stage of Decision Making" to investigate women's decision making process regarding participation in screening, 2) Questionnaire with choice framing (presentation of a choice between participation in breast cancer screening or no screening), or 3) Questionnaire with opportunity framing (only presentation of screening, no alternative) to investigate decision making process and impact of different framing. The main hypothesis for this study is that 80% of Danish women have already made their decision about screening participation when presented to the opportunity framing and 70% when presented to the choice framing.
1000 women will be invited to each group in this study and thus 3000 in total, as this is the minimum number satisfying the requirements for both the main hypothesis and secondary aims (not described in detail here). No similar studies were found, therefore, this sample size calculation is based on proportions of 50% to have enough power in our study. With a desired standard error no larger than 2.5%, 400 women are required (SE of a binomial random variable). Assuming 40% participation, a study population of 1000 women in each group is required.
Next, questionnaire data will be linked to register data on sociodemographic factors from Statistics Denmark.
The study is registered at Aarhus University's internal records: 2016-051-000001, 2563.
