Kim EY, Chang Y, Ahn J, et al. - Among premenopausal and postmenopausal women researchers examined the link between breast density and its alterations over time with the development of breast cancer by analyzing a cohort of middle‐aged Korean women (n = 74,249, aged ≥ 35 years) free of breast cancer at baseline. They defined a dense breast as heterogeneously dense or extremely dense; they categorized changes in dense breasts seen between baseline and subsequent follow‐up as none, developed, regressed, or persistent dense breast. A median follow‐up was 6.1 years. Among premenopausal and postmenopausal women, a greater risk of incident breast cancer was linked to both baseline dense breasts and their persistence over time. The multivariable‐adjusted hazard ratios for breast cancer comparing nondense breasts to “heterogeneously dense” was 1.96 and for “extremely dense” was and 2.86.