Forever Smart: Does Estrogen Enhance Memory?
Fackelmann, Kathy, Science News
Touted in 1950s as an elixir that would keep postmenopausal women forever feminine and vilified in the 1970s as a cause of cancer, estrogen replacement therapy has had a checkered history.
Yet doctors now know that this drug provides many benefits to women who have gone through menopause. Estrogen shields women from the potentially crippling bone loss of osteoporosis and can slash their risk of heart disease.
Despite the huzzahs given this therapy of late, however, many older women don't take estrogen, perhaps because of a lingering fear of cancer. There's little doubt that estrogen, when taken by itself, magnifies the risk of endometrial cancer. Yet doctors can mitigate this cancer threat by giving estrogen in combination with another hormone called progesterone.
That strategy has done little to assuage another cancer worry, though. Researchers know that a woman's cumulative exposure to her own body's estrogen increases the risk of breast cancer. Unfortunately, studies on the link between estrogen pills and breast cancer have produced conflicting results.
Several research teams, however, now add some more good news to the complex risk-benefit picture of estrogen replacement therapy. Their data suggest it boosts short-term memory and the ability to learn new tasks. In addition, one team suggests that estrogen replacement therapy may counter depression.
"Estrogen has been shown to influence several areas in the brain that are involved in cognition and behavior," says researcher Uriel Halbreich of the State University of New York at Buffalo.
At the same time, a California team reports data hinting that estrogen replacement therapy shields -- at least partially -- against Alzheimer's disease, a degenerative disorder of the central nervous system (see sidebar).
Is menopause a disease or simply a natural consequence of aging? Proponents of the disease model point out that at the turn of the century, most women didn't live long past menopause: In fact, only 5 percent of women lived beyond their 50th birthday. However, most U.S. women alive today can expect to spend one-third of their life in that estrogen-deficient state.
Menopause is a dramatic event. Ovarian production of estrogen declines from as much as 300 micrograms per day to almost nothing. Yet postmenopausal women still manufacture up to 20 micrograms of estrogen per day in the liver and fatty tissue.
Women prescribed estrogen replacement therapy have a choice of natural or synthetic estrogen. The most popular product, Premarin, is estrogen derived from the urine of pregnant horses.
With antibiotics, improved diets, and the everyday miracles of modern medicine, humans have expanded their life span. "In a way, we've created this phenomenon of old age," says psychologist Barbara B. Sherwin of McGill University in Montreal.
The theory behind estrogen replacement therapy is that women should be able to avoid the numerous undesirable consequences of menopause, including osteoporosis and hot flashes. Sherwin and other researchers believe it makes sense to supply in pill form the estrogen the body stops manufacturing.
As one ages, it takes longer to remember names and other facts once retrieved without hesitation. While memories of long ago remain sharp, an older person may have difficulty recalling a new telephone number.
Sherwin knew that some research on animals suggested a link between estrogen and memory. In rats, for example, estrogen increases the amount of an enzyme necessary for synthesis of acetylcholine, a neurotransmitter that plays a key role in memory. She wondered whether older women could improve their memory by taking hormone therapy
Diane L. Kampen, also at McGill, and Sherwin began to study this question by recruiting healthy women age 55 and over who had completed menopause at least 2 years earlier. The duo ended up with 28 women in estrogen replacement therapy and 43 who were not. …