Mammographic density mediates the protective effect of early-life body size on breast cancer risk

A study delves into the mysterious link between childhood obesity and reduced breast cancer risk, potentially attributed to mammographic density (MD). Through Mendelian randomization (MR) analysis, researchers uncover that childhood adiposity decreases dense area (DA) on mammograms, while adult obesity increases non-dense area (NDA). Later onset of menarche amplifies DA/percent density (PD) but this effect diminishes when childhood adiposity is considered. MD, particularly DA/PD, increases breast cancer risk, albeit with varying genetic influences. Notably, 56% of childhood obesity's protective effect on breast cancer is mediated through reduced DA. Understanding this mechanism could aid in targeted interventions.