Abstract
BACKGROUND: Breast density (BD) is an independent risk factor for breast cancer and reduces the sensitivity of mammography. This systematic review aims to synthesize evidence from existing studies to understand the impact of BD information and/or notification on women's cognitive, psychological, and behavioral outcomes. METHODS: Studies were identified via relevant database searches up to March 2020. Two authors evaluated the eligibility of studies with verification from the study team, extracted and crosschecked data, and assessed the risk of bias. RESULTS: Of the 1134 titles identified, 29 studies were included. Twenty-three studies were quantitative, including only 1 randomized controlled trial of women receiving BD information, and 6 were qualitative. Twenty-seven studies were conducted in the United States, with 19 conducted post-BD legislation. The overall results in terms of BD awareness, knowledge, attitudes, perceptions, and intentions were heterogeneous across included studies, with the strongest consistency demonstrated regarding the importance of communication with and involvement of health-care professionals. Together, the studies did, however, highlight that there is still limited awareness of BD in the community, especially in more socioeconomic disadvantaged communities, and limited knowledge about what BD means and the implications for women. Importantly, BD information in the context of overall breast cancer risk has not yet been studied. CONCLUSIONS: There are important gaps in the understanding of the impact of BD information or notification on women and how best to communicate BD information to women. More high-quality evidence to inform both current and future practice related to BD is still needed.