Women who had their ovaries removed before menopause, particularly before the age of 40 were found to have reduced white matter integrity in multiple regions of their brain later in life, according to a study published in Alzheimer's & Dementia: The Journal of the Alzheimer's Association.
What is white matter?
White matter refers to a network of nerve fibers that connect neurons in different areas of the brain allowing for high-speed communication and information exchange in different regions. White matter is located beneath the gray matter cortex and makes up about half of the brain. It is made up of millions of axons (nerve fibers) that are extensions of nerve cells (neurons) that are covered in a protective myelin sheath.
White matter plays an important role in brain health, helping to process information and connecting regions that send/receive signals. This role affects many important functions such as focus, learning, solving problems, complex skills, cognitive function, and balance. Changes in white matter can impair conduction and lead to cognitive impairment, long-term neurological problems, or other conditions that could also be progressive.
“We know that having both ovaries removed before natural menopause causes abrupt endocrine dysfunction, which increases the risk of cognitive impairment and dementia,” said Michelle Mielke, Ph.D., professor and chair of epidemiology and prevention at Wake Forest University School of Medicine. “But few neuroimaging studies have been conducted to better understand the underlying mechanisms.”
The study
For this study, data was examined from the Mayo Clinic Study of Aging to identify women over the age of 50 with available diffusion tensor imaging, a magnetic resonance imaging (MRI) technique to measure white matter in the brain. The cohort included 22 participants who had premenopausal bilateral oophorectomy (PBO) before age 40, 43 participants who had PBO between the ages of 40 and 45, 39 participants who had PBO between the ages of 46 and 49, and 907 participants who did not have PBO before the age of 50.
What they found
“Females who had premenopausal bilateral oophorectomy before the age of 40 had significantly reduced white matter integrity in multiple regions of the brain,” said Mielke, the study’s corresponding author. “There were also trends in some brain regions such that women who had PBO between the ages of 40-44 or 45-49 years also had reduced white matter integrity, but many of these results were not statistically significant.”
More research is needed
The ovaries secrete hormones before and after menopause. It was noted that 80% of those who had their ovaries removed also had a history of estrogen replacement therapy. Thus the study was not able to determine whether the use of estrogen replacement therapy after PBO mitigated the effects of PBO on white matter integrity.
“Having both ovaries removed results in an abrupt decrease in both estrogen and testosterone in women,” Mielke said. “Therefore, one possible explanation for our results is the loss of both estrogen and testosterone.”
“While these findings are important for women to consider before having premenopausal bilateral oophorectomy for non-cancerous conditions, we need a larger and more diverse cohort of women to validate these results.”
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