Women who begin taking hormone replacement therapy (HRT) within five years of the menopause may reduce their risk of developing Alzheimer's disease. Scientists monitored 1,768 women aged 65 and over for 11 years, taking note of their history of HRT use. During the study, 176 women developed Alzheimer's disease. The researchers found that women who started HRT within five years of the menopause had a 30% lower risk of Alzheimer's than those who had not used hormone therapy. The risk was unchanged among HRT users who began the treatment more than five years after the menopause.