Scientists will know by 2005 whether estrogen replacement therapy delays the onset of Alzheimer’s disease in aging women, according to Barbara Sherwin, Professor in the Departments of Psychology and Obstetrics and Gynecology at McGill University.
Sherwin is one of the world’s leading researchers on the effects of estrogen in relation to memory and cognitive function. This spring, the Canadian Institutes of Health Research awarded a 5-year Distinguished Scientist Award in the Health Research category to the Professor for her studies of steroid hormones and cognitive function in older women. She plans now to investigate the possible role of testosterone, another hormone also produced by the ovaries, on aspects of cognition in women.
Although her research findings have shown that estrogen protects against some decline in explicit memory in healthy aging women, Dr. Sherwin cautions that does not mean that it will cure Alzheimer’s Disease. “There is little or no evidence so far that estrogen can reverse the memory loss that occurs in Alzheimer’s Disease, possibly because these women have already lost too many brain cells by the time a diagnosis has been made. However, several studies have shown that estrogen replacement therapy reduces the incidence of Alzheimer’s Disease in older women,” said Dr. Sherwin.
Sherwin emphasizes that memory loss is not inevitable with age, but it is our skills in dealing with new information that become blunted. Estrogen replacement therapy may have a positive benefit on this ability to continue to learn and process information as we age:
“Normal aging does not affect immediate memory in older people. It functions as well as it did when they were 30 years of age. The same goes for remote memory,” says Sherwin, “However, our capacity to learn – to code new information, to consolidate and retrieve it – that decreases with aging. Our studies have found that estrogen replacement therapy prevents some of the decline in the ability to learn and to remember new material in postmenopausal women.”
Men’s and women’s bodies make both estrogen and androgen, albeit in different quantities. The ovaries make over 90% of the estrogen in women and, after the menopause, they are unable to produce it any longer. Although men’s glands make only small amounts of estrogen, an enzyme converts some of their testosterone into estrogen. Also, men continue to produce testosterone lifelong, although in smaller amounts as they age, while menopause puts an end to women’s reproductive hormone production in their early fifties. This affects, among other things, verbal memory for the latter one-third of their lifespan.
In 1988, Dr. Sherwin published the first hard evidence that estrogen maintains verbal memory and enhances the capacity for new learning in postmenopausal women. Later, she showed that estrogen replacement therapy had the same effect on women in their late thirties and early forties who suffered a sudden drop in circulating levels of estrogen after their ovaries and uterus had been surgically removed.
“Women who were given a placebo after their surgery complained of not being able to remember things, of having to make lists, which they never needed to do in the past, and also had lower scores on tests of verbal memory,” said Dr. Sherwin. “On the other hand, women who were randomly treated with estrogen postoperatively maintained their scores on the same tests of memory. What estrogen seems to do is to prevent some of the decline in the ability to learn and to remember new material after the menopause.”
Dr. Sherwin is a member of the external advisory board of the Women’s Health Initiative Memory Study, a large longitudinal study funded by the U. S. National Institutes of Health involving 26 clinical sites across the United States. In 1995-1996, 10,000 women over the age of 69 were randomly assigned to treatment with estrogen or placebo for 9 years to determine whether estrogen reduces the incidence of Alzheimer’s Disease