1) The study examined how health behaviors like BMI, physical activity, alcohol consumption, and smoking affected mortality outcomes in 1,925 women diagnosed with ductal carcinoma in situ (DCIS). 2) Over an average of 6.7 years of follow up, 196 deaths occurred including 87 from cancer and 34 from cardiovascular disease. 3) Current smoking one year prior to DCIS diagnosis was associated with over twice the risk of all-cause mortality compared to never smokers. Greater physical activity levels prior to diagnosis were associated with half the risk of all-cause mortality. Moderate physical activity after diagnosis was linked to over two-thirds reduced risk of all-cause mortality.