Subtle effects, if any, have been found across cross-sectional studies and prospective studies, which have, at most, 24 months of follow-up3,5–8 The potential interaction between APOE ε4 and long-term anti-estrogen endocrine therapies in breast cancer survivors is especially important given evidence of sex differences in the risk of APOE ε4-associated dementia and the potential influence of changes in hormonal functioning on dementia risk in aging women9–11. The gene discussed is APOE; the disease is breast cancer.