MONDAY, Jan. 14, 2013 (HealthDay News) -- The younger a woman is when she undergoes surgical menopause, the greater her chances of developing memory problems at an earlier age, new research suggests.
Surgical menopause describes the end of ovarian function due to gynecological surgery before the age of natural menopause. It involves the removal of one or both ovaries (an oophorectomy), often in combination with a hysterectomy, the removal of a woman's uterus.
"For women with surgically induced menopause, early age at menopause was associated with a faster decline in memory," said study author Dr. Riley Bove, an instructor in neurology at Harvard Medical School and an associate neurologist at Brigham and Women's Hospital in Boston. However, she stressed, "These are very preliminary data."
Bove said other research suggests a link between a decrease in the hormone estrogen during menopause and mental decline, and the aim of this study was to better understand the relationship between reproductive-health factors and memory changes. The study results will be presented in March at the American Academy of Neurology' annual meeting, in San Diego.
For the study, the researchers analyzed medical records of more than 1,800 women aged 53 to 100 who were taking part in one of two studies conducted by Rush University Medical Center in Chicago: the Religious Orders Study and the Memory and Aging Project.
The researchers assessed reproductive variables, such as when women had their first period, the number of years menstrual cycles lasted, and use of hormone replacement therapies. Measurements from several types of thinking and memory tests were analyzed, too. The scientists also assessed the results of brain biopsies after death, some of which showed the presence of Alzheimer's plaques.
"We had approximately 580 brains available for analysis -- this speaks to the very unique and rich nature of the data," said Bove.
Thirty-three percent of the study participants had undergone surgical menopause.
Reasons for these surgeries may include fibroids (noncancerous uterine tumors), endometriosis (growth of uterine tissue outside the womb), cancer of the uterus and ovaries, and abnormal vaginal bleeding. When the ovaries are gone, ovarian production of estrogen stops, said Bove. However, this study did not include reasons why the women underwent surgical menopause.
Even after factoring in smoking and education levels, the investigators found an association between women who underwent surgical menopause when they were younger and a faster decline in long-term memory, said Bove.
"We did not see an association in women who underwent natural menopause, but this doesn't mean there isn't an association," she added. There was also an association between age at surgical menopause and the plaques in the brain connected with Alzheimer's disease. But association does not prove cause and effect.
The findings make sense, said Dr. Jocylen Glassberg, an obstetrician/gynecologist at Scott & White Hospital in Round Rock, Texas.
"There was another study recently that linked heart disease to early surgical menopause. To me, it makes sense that the same processes that affect your heart would affect your brain. Plaques in the heart and brain are related. Even though this is preliminary, I bet it pans out," Glassberg said.
Patricia Moorman, an epidemiologist and associate professor in the department of community and family medicine at Duke University Medical Center, who has studied hysterectomy, said it's known that estrogen has numerous beneficial effects on the body, including the brain, but it's not clear why.
"Hormone supplementation is such a complex issue," said Moorman. "There are so many potential benefits of estrogen replacement therapy but also potential harms, so you are always weighing those issues."
It's known that there are estrogen receptors in the brain, said Glassberg, but it's not clear why estrogen may be good for memory. "No one knows what the magical link is there. I think the brain is one of the last big frontiers of medicine."
Duke's Moorman said it's too early to change clinical practice for surgical menopause patients. "This is just one part of the evidence on this topic. The data aren't conclusive," Moorman said.
She also noted that because many of the participants were nuns, the research may produce different results in another population of women. "They are not a typical group of women. They have not gone through childbirth, whereas 80 percent of the population has," said Moorman.
Bove concurred, saying "ongoing research into the potential neuroprotective effect of hormone therapy after early surgical menopause is warranted."
Research presented at medical meetings is typically considered preliminary until published in a peer-reviewed journal.
The U.S. Department of Health and Human Services Office on Women's Health has more about surgical menopause.