Strong Association Between Cervical and Breast Cancer Screening Behaviour Among Danish Women; A Register-based Cohort Study

High coverage is essential for the effectiveness of national screening programmes. Identifying non-screeners across different screening programmes may help inform strategies to improve uptake. This study aims to analyse the association between previous cervical cancer screening (CCS) coverage and participation in breast cancer screening (BCS). This historical register-based cohort study included 91,787 Danish women aged 50-64 years who were invited to participate in the first organised round of BCS in the Central Denmark Region (CDR) in 2008-09. CCS coverage was defined as having a smear registered in the 5 1/2 years preceding the BCS, and BCS participants were divided into participants and non-participants and further categorised as active non-participants (ANP) if they cancelled and passive non-participants (PNP) if they abstained from the appointment. Of all 91,787 women included in the study, 62,391 (68%) were covered both by CCS and participated in BCS. Women not covered by CCS were more likely to be non-participants in BCS than women covered by CCS (PRRadjusted = 2.80, 95% CI: 2.68-2.93). Both PNP (PRRadjusted = 3.99, 95% CI: 3.80-4.19) and ANP (PRRadjusted = 2.50, 95% CI: 2.34-2.68) were more likely not to be covered by the CCS. In conclusion, non-coverage by CCS was strongly associated with nonparticipation in BCS. Specific groups of women only participated in one screening programme. To increase uptake, future interventions may specifically target these groups.