At the time of menopause, each woman has a window of opportunity during which she needs to make the important decision of whether to take hormones. As the estrogen levels fall, her body begins to go through degenerative changes that accelerate her risk of heart disease along with the other changes we have previously described. The sooner a woman starts HRT after menopause, the fewer degenerative changes she will experience. If a woman waits 10 years to start HRT, the heart protection from estrogen is greatly diminished. The same applies brain protection; once brain cells have been lost, it becomes difficult to retrieve normal function. However, for protecting bones, estrogen is effective even when started after age 75.