More than one in three women in North America experience sexual violence at least once over the course of their lives. That's according to statistics published by the US Centers for Disease Control and Prevention (CDC).

Globally, the number is roughly the same: An estimated 736 million women across the world "have been subjected to intimate partner violence, non-partner sexual violence, or both at least once in their life," writes the United Nations body UN Women. It cites a study by the World Health Organization. 

That amounts to 30% of all girls and women aged 15 years and older.

So, the problem is pervasive. And now, a US study has found that women who experience sexual violence might be confronted with more than the injuries sustained during the attacks, as well as the mental health consequences like post-traumatic stress disorder, anxiety, or depression. They may also have a higher risk of a certain type of brain disease that's a precursor for dementia and stroke.

"Sexual assault is an unfortunate, yet all-too-common, experience for women," says Rebecca Thurston from the University of Pittsburgh, lead author of the study. 

"This distressing experience is not only important for women's mental health, but also their brain health. This work is a major step toward identifying a novel risk factor for stroke and dementia among women," says Thurston.

Trauma can disrupt blood flow in the brain

Thurston is a professor of psychiatry and the director of the Women's Biobehavioral Health Laboratory at the University of Pittsburgh. She presented the results of the study at the 2021 meeting of the North American Menopause Society. It will be published in the journal Brain Imaging and Behavior.

For the study, Thurston and her team examined 145 women of "midlife" age in the US. Of the participants, 68% reported having had at least one trauma, with the most common trauma being sexual assault reported by 23% of the women.
 

The researchers wanted to find out whether there was a connection between trauma and white matter hyperintensities, which are signs of disruptions in blood flow and can leave damage in the brain. 

White matter hyperintensities show up as small white spots on brain scans. They are early indications of dementia, risk of stroke or similar disorders. And they can be detected decades before the onset of those conditions.   

Brain scans of the study participants showed that the women who had experienced a trauma had more white matter hyperintensities than women without trauma ― and that the specific traumatic experience associated with the white matter hyperintensities was sexual assault.

Crucial data to detect high-risk early

In an earlier study in 2018, Thurston had found that women who had experienced sexual assault had significantly higher chances of developing depression or anxiety, and of sleeping more poorly than women who had not been assaulted. 

Depression, anxiety and sleep disorders have all been linked to poor overall health. 

Mental health disorders can be linked to heart disease, for example, and a lack of sleep can be linked to high blood pressure, type 2 diabetes and obesity.

Thurston says the new study builds on those earlier results. Even when the researchers had accounted for mental or other health conditions in the new study, they found that women who had been assaulted still had more white matter hyperintensity — irrespective of whether they had developed other health problems, like depression or PTSD after an assault. 

The bottom line is that those early signs of dementia can be directly linked to the assault, according to the study. 

Thurston says the research shows there's a need for better sexual assault prevention, but that it also shows doctors there's another indicator to consider when they assess a female patient's risk for stroke and dementia later in life.

Stephanie Faubion, a medical director of the North American Menopause Society, says the new study can play an important role in preventative healthcare.

"Identifying early warning signs of stroke and dementia is critical to providing effective intervention," says Faubion.

"Studies like this one provide important information about the long-term effects of traumatic experiences on a woman's overall well-being and mental health."