A large study published in 2016 by researchers at the University of California, San Francisco, using data from over 200,000 Kaiser Permanente patients in six racial groups found that the risk of dementia was 65 percent higher for Black people than for the lowest risk group, Asian Americans. A 2019 study found that the incidence of Alzheimer’s disease dementia was twice as high for Black people as for white people.

“Studies draw from different populations, so part of the explanation may be inherent in the specific study sample for a given study,” Fann points out. He also notes that because dementia risk is already higher for Black patients, the added event of a head injury might not be enough to increase that baseline risk.

Barnes notes that, in the case of the University of Pennsylvania study, because the data relies on self-reporting, it’s also possible that male and Black participants were less likely to report accurately, so the data may not be conclusive.

Schneider was surprised by her study’s findings and acknowledges that the data on these racial and gender differences doesn’t tell the whole story. “There’s a great deal more work that is needed to be done to look at reasons why we may have observed these differences,” says Schneider.

The researchers hope that by understanding who is most harmed by head injuries and how it elevates the risk of dementia, there may be something scientists can do to mitigate their effects. But that goal is still far off. “First, we need to understand these short-term and long-term associations with head injury before we can really think about devising treatment strategies and interventions,” says Schneider.

Right now, if you do suffer a brain injury, there isn’t a lot that one can do to specifically reduce dementia risk. “What we’ve been recommending is that people need to pay attention to all the risk factors that they may have for dementia,” Schneider says. That means making sure patients attend to modifiable behaviors like controlling their blood pressure, cholesterol, and blood sugar levels. “All of these things that we would actually recommend for everyone, it might be that they’re actually more important for these people that have this other risk of having had a traumatic brain injury,” she says.

But Schneider says that research into brain injuries has already improved patient care by making people more aware of the risks that even mild concussions can present. “I think that what people think about as a serious head injury has actually changed over the years,” she says. “Back 50 years ago, people would just go about their business unless they had to be taken to the hospital or were exceptionally symptomatic.” Now, school and sports leagues have concussion protocols and are less likely to send players back onto the field after they’ve sustained a blow to the head.

Schneider is planning to do further research about how brain trauma might exacerbate the vascular risk factors for dementia and is hoping to learn more about the specific age, sex, and racial factors that contribute to dementia. That way, doctors can start to develop customized treatment plans for brain injury patients. At this point, she says, the biggest lesson is that the more brain trauma you have, the greater your risk of developing dementia becomes.

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