A recent study has shown that a 3 month trial of estradiol (E2) significantly improved cognition in women with early Alzheimer’s. Notice that synthetic progesterone (medroxyprogesterone) was used concurrently.
http://www.med.wisc.edu/news-events/news/natural-estrogen-may-improve-cognition-for-alzheimers-disease-patients/31756
Another recent study showed that women who took 1mg of estradiol (bioidentical E2) over three months  developed more gray matter in the parietal, temporal and prefrontal areas of the brain, areas that are known to be involved in attention, decision-making and memory. The development of more gray matter may be linked to improved cognitive abilites.

http://news.vanderbilt.edu/2011/11/estrogen-increase-gray-matter/

Both of these studies are part of the growing evidence that bioidentical estrogen replacement should be considered for women who have a family history of Alzheimer’s.  In additon it is noted that in older people (age 67) who complain of memory slippage, 50 percent eventually go on to develop dementia. Therefore complaints of memory disturbances at the time of menopause whould be taken seriously.