We investigated the outcomes of all-cause mortality and BC-specific mortality given that (1) 27-HC is suggested to have a role in multiple physiologic processes and (2), 27-HC binds to the estrogen receptor in tissues beyond breast cancer; evaluations stratified by estradiol were conducted given previous experimental and other epidemiological studies suggesting actions of oxysterols may depend on the background estrogenic environment. Here, ESR1 is linked to breast cancer.