"Abstract

The consumption of ultra-processed foods (UPF) continues to rise globally, and UPF consumption is associated with elevated risk of mortality due to cancers and cardiovascular events. However, whether UPF consumption is associated with breast cancer and its mortality remains controversial. In this study, we aimed to examine the association of UPF consumption with breast cancer incidence and breast cancer mortality based on a large US population-based cohort. Herein, 2245 breast cancer cases and 270 breast cancer deaths were identified during 445,998 person-years of follow-up. Cox regression and competing risk regression were used to estimate multivariable-adjusted hazards ratios (HRs) and 95% confidence intervals (95% CIs) by UPF consumption for risk of breast cancer incidence and mortality. After adjustment for confounders, UPF consumption was associated with an increased risk of breast cancer incidence (Quintile(Q)2 vs. Q1, HR for Q2 vs. Q1: 1.16; 95% CI, 1.01–1.34, P = 0.04) and showed a trend toward increased mortality (Tertile(T)3 vs. T1, HR: 1.33, 95% CI, 0.99–1.80, P = 0.06). Subgroup analyses revealed stronger associations between UPF intake and the breast cancer risk in older participants (> 65 years, Q5 vs. Q1, HR: 1.41, 95% CI, 1.12–1.78), alcohol drinkers (Q2 vs. Q1, HR: 1.18, 95% CI, 1.02, 1.37), and those with a family history of breast cancer (Q3 vs. Q1, HR: 1.45, 95% CI, 1.00, 1.95). These findings suggest that higher UPF consumption may slightly increase breast cancer risk and mortality, particularly among women with breast cancer-related lifestyle factors and family history. These findings highlight the need for large cohorts to validate subgroup-specific associations and inform personalized cancer prevention."