Interview: The link between the uterus and cognitive function

December 6, 2018

Newly published research has challenged a long-standing belief in the medical community that uteruses serve no purpose in the body except pregnancy. When researchers at Arizona State University performed hysterectomies on rats, the animals’ memory suffered. Hysterectomy, the removal of a woman’s uterus, is an extremely common surgery. The procedure can be life-changing for women who need it, like those suffering from painful conditions or cancer. But some research suggests the surgery is frequently performed unnecessarily. Seeing the need to better understand how hysterectomies affect women’s health, researchers Stephanie Koebele and Heather Bimonte-Nelson investigated. We spoke with Bimonte-Nelson to learn more about what they found.

Researchers Stephanie Koebele (right) and Heather Bimonte-Nelson in the lab. Credit: Robert Ewing, ASU

ResearchGate: How routine are hysterectomies?

Heather Bimonte-Nelson: In the US, for women in their reproductive years, hysterectomy is the most common major surgery after cesarean section. Each year there are over 600,000 hysterectomies performed in the US. Approximately one-third of women experience hysterectomy by age 60.

RG: Why hasn’t research like yours been done before?

Bimonte-Nelson: I believe there has not been a large amount of research in this area because the dogma in the field is that the nonpregnant uterus is dormant, and therefore it has not necessarily been of interest to study. Textbooks have described the nonpregnant uterus as “quiescent,” “dormant,” and “useless.” When I was in graduate school studying endocrinology, I read statements in books saying that the sole purpose of the uterus is for gestation.

RG: How did you study the link between surgery and memory?

Bimonte-Nelson: Using a rat model of hysterectomy, we tested the effects of uterus removal alone (hysterectomy), ovarian removal alone, or uterus plus ovarian removal. Then, we tested the ability of rats to use their spatial memory. Spatial memory is the ability to navigate and find the way through the world using cues in the environment. An example in humans would be navigating to the grocery store from your house. We tested both working memory and reference memory in the spatial test.

“This study is the first of its kind.”

RG: What did you find?

Bimonte-Nelson: We found that surgical removal of the uterus alone can impair working memory two months after surgery, especially when memory was highly taxed. There was no memory impairment when the ovaries were removed along with the uterus. These results show a unique negative effect of hysterectomy alone on memory. They indicate that the uterus is part of a system which communicates with the brain for functions like cognition.

RG: What could explain a possible link between the uterus and memory?

Bimonte-Nelson: We believe there is a uterus-ovary-brain triad that might impact brain functions such as memory. Although the reason why hysterectomy impacts cognition is not yet understood, we believe hysterectomy yields a unique disruption in this whole system that is different than the disruption that occurs with removal of just the ovaries.

Credit: Robert Ewing, ASU

RG: You tested the rats six weeks after surgery. Do you think the memory issues could be long-lasting or even permanent?

Bimonte-Nelson: Whether these effects are just temporary or are long-lasting is a critical question. It is possible that a disruption to the system results in a temporary adjustment period, where the body is trying to acclimate to the loss of the uterus. It is also possible that the effects of the uterus loss are long-lasting and not reversible, with detrimental effects progressing and worsening with time. We have just received grant funding from the National Institutes of Health to follow up on this work and to address this important question. We should have an answer in the next year when this next study is completed. We have so much more to learn.

“While the female body is complex, complex does not mean impossible to understand”

RG: Do your results change what we know about the role of the uterus?

Bimonte-Nelson: This research is significant because the dogma in the field is that the uterus is a dormant organ when it is not in a pregnant state. Our findings suggest that the nonpregnant uterus is not quiescent, and is in fact linked to brain functioning. This study is the first of its kind. We hope that these basic findings will lead to additional attention and focus on how different menopause surgeries might impact the brain and its functioning in women, ultimately impacting their quality of life.

RG: If hysterectomies are found to have a similar effect in humans, do you expect medical guidelines would be changed?

Bimonte-Nelson: There has been some human research showing that there is an increased relative early-onset dementia risk in women who underwent hysterectomy, particularly when the surgery occurred at younger ages. However, there is also a study showing the opposite effect, with a benefit of hysterectomy in older women. The factors driving hysterectomy’s effects on brain functioning and dementia risk must be determined so that medical recommendations can be updated accordingly. We do not have enough information to do this at this time.

We have learned a lot about women’s health in the last decade, but we have a lot more to go before the puzzle shows us a clear picture. While the female body is complex, complex does not mean impossible to understand. The results from this research underscore the essential need to further study the contribution of the uterus to overall female health and well-being.

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Featured image courtesy of Robert Ewing, ASU.

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