" The strongest data to suggest a link between menopause and Alzheimer’s disease comes from longitudinal studies that follow women who transition through menopause early. Those studies surgically induced menopause. Women who had menopause induced before the age of 50 had a 70 percent increased risk of cognitive impairment or Alzheimer’s disease as they aged. The good news is that that increased risk was completely offset by the use of estrogen-alone up until the age of 50. Then there’s a question about whether or not the fact that women transition through menopause might be responsible for the data that shows two-thirds of Alzheimer’s patients are female. That increased frequency of Alzheimer’s disease among women compared to men is driven by women’s longevity. Women’s longevity is the biggest risk factor for Alzheimer’s since women live longer than men. There is, however, some suggestion that estrogen might offset some of the pathology of Alzheimer’s disease. This idea that hormones are safer for younger women is known as the critical window hypothesis and those data provide women with some reassurance that if they treat their vasomotor or menopausal symptoms early, it’s safe, whereas delaying might be detrimental. "