Thursday, July 12, 2001 (HealthDayNews) -- Starting hormone replacement therapy sooner rather than later could be the key to helping women keep their memory sharp well into their senior years.
So say researchers at the Mount Sinai School of Medicine in New York City, where animal studies showed the younger you are when you start estrogen therapy, the more likely you are to reap the memory-related benefits of this hormone.
"We were looking for two kinds of changes that might augment memory -- one is the actual structural change in the number of synapses, or connections between nerve cells, and the other is a change in the biochemistry of what happens at the site of synapse itself," says study author John Morrison, professor and director of the center for neurobiology at Mount Sinai.
"What we found was that the young animals actually showed an increase in the number of synapses in response to estrogen, which is about the most profound change that you can have with respect to memory," Morrison explains.
The ability to remember comes from two different brain functions, he says. The first involves message centers -- the synapses -- in the brain that send communications from cell to cell. The greater your number of message centers, says Morrison, the better your memory. The second function involves what actually takes place at these message centers -- the "brain chemistry" that lets cells communicate.
In the younger rats, says Morrison, estrogen played a role in both types of circuitry, creating new message centers and increasing the amount of neurochemicals available for cell communication.
However, the benefits of this hormone were not completely lost on the older animals. While estrogen couldn't help those rats develop new message centers once their natural supply had begun to die out, it increased the production of neurochemicals linked to memory.
"The young animals did benefit more, but clearly estrogen was helpful to both groups," says Morrison.
The findings don't surprise Dr. Michele Warren.
As director of the Center for Menopause and Hormonal Disorders at Columbia Presbyterian Medical Center in New York City, she sees a similar age-related pattern in the effects of estrogen on women, not just with memory but also with other benefits that include protection against cardiovascular disease.
"Starting hormone replacement therapy before rather than after menopause does seem to have more benefit for many women -- it seems that the most beneficial effects of estrogen are largely preventive in nature. So the sooner you begin taking it, the more likely you may be able to prevent some types of damage that leads to disease," says Warren.
The study, which appears in the July 3 issue of The Proceedings of the National Academy of Sciences, involved 18 female rats. Nine were considered to be equal to the pre-menopausal age of women, and nine were equal to post-menopausal age.
The ovaries of both groups of animals were removed, thus stopping natural estrogen production. Seven days later, doctors implanted tiny capsules filled with estrogen into the rats. Dosages were weight- and age-related.
The final result: Brain biopsies revealed the younger the rats were when the estrogen therapy was started, the greater the impact the hormone had on memory circuitry. Conversely, the older the rats were at the time of the estrogen implant, the less the brain was able to respond to the hormones.
"Essentially, once the synapses were destroyed, which is something that happens gradually as we age, estrogen could not bring them back. But when taken early enough, the hormone was able to encourage the development of new synapses -- and that was an important finding," says Morrison.
Warren agrees: "This is consistent with what we are seeing in women, in terms of the protective effects of estrogen on many areas of the body, when the therapy is started early enough."
Most recently, studies that looked at estrogen and the risk of cardiovascular disease in women found the effects of the hormone may not be as protective as once thought. Researchers like Warren and Morrison, however, say those findings may be related to the age of the women when they started the therapy -- a theory this new study appears to validate.
"It's likely that the positive effects of estrogen will be largely in preventing disease, rather than in correcting damage after it has already occurred," says Morrison.
What To Do
For a listing of government-sponsored clinical trials on memory and estrogen therapy, click here.
To learn more about the effects of hormones on aging, visit the National Institute on Aging.
To read more about natural ways to combat estrogen loss associated with aging, click here.
