Conflicting data have led to uncertainty over the effect of hormone therapy on risk of Alzheimer disease (AD): some observational studies report a reduced risk, whereas clinical trials suggest an increased risk of AD following hormone therapy. In a recent population-based study, Shao et al. assessed whether the association between hormone therapy and AD varies with the type or timing of therapy. 1,768 women were included in the study, with follow-up over an 11-year period. During this time, 176 individuals developed incident AD. Use of hormone therapy within 5 years of menopause was associated with a 30% decrease in AD risk. However, initiation of hormone therapy beyond this 5-year window carried an increased risk of disease.