UC Davis researchers announced Tuesday that, after studying brain tissue from 423 Americans of Latino, African and non-Hispanic white descent, they have discovered startling variations in the causes of dementia among people of different races and ethnicities.
In Latinos, for instance, cerebrovascular disease was much more likely to be a cause of dementia than Alzheimer’s disease. Among Hispanics diagnosed with dementia, 21 percent had cerebrovascular damage and 54 percent had a combination of both Alzheimer’s disease and cerebrovascular degeneration.
Among blacks whose brains were studied, 11 percent showed signs of only cerebrovascular damage, and 37 percent of them had both Alzheimer’s disease and cerebrovascular disease.
“It looked very clear to us that vascular disease plays a much stronger role in the Latino population, and is a contributing factor in the black population and that it may account for an overall higher incidence of dementia in these groups,” said Dr. Charles DeCarli, director of the UC Davis Alzheimer’s Disease Center and the principal investigator on the study.
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The findings led UCD neuropathologist Brittany Dugger, one of the authors of the research published today in the Journal of Alzheimer’s Disease, to say that Latinos could reduce their risk of getting dementia by adopting a heart-healthy diet and staying on top of chronic conditions such as hypertension and diabetes.
“Many people...can have these vascular risk factors, but a lot of them can remain untreated,” Dugger said. “If they were treated for their vascular disease, it could decrease their risk of dementia later. If you have hypertension, get on anti-hypertension medication, eat well, and exercise. Those are the biggest things I could tell everybody.”
The research, published today in the Journal of Alzheimer’s Disease, may help to explain the higher incidence of dementia among Hispanic and African Americans, said Dugger, who joined the University of California, Davis, a year ago because she wanted to study disease progression across diverse racial groups. Her team said this particular study is the first to extensively analyze autopsied brains to gain insights into the distinct causes of dementia by race.
Latino and African-American patients should work aggressively with their medical care teams to address the risks, said DeCarli, a neurologist. The findings allow medical providers to tailor their messaging, treatment and approach to individuals, he said, and that should be done as early as possible to prevent vascular damage.
Non-Hispanic whites whose brains were studied had the lowest incidence of cerebrovascular disease – 4 percent – among the three racial groups. Roughly 43 percent of both non-Hispanic whites and blacks in the study had dementia caused by pure Alzheimer’s disease. Like African Americans, 37 percent of whites in the study showed signs of both cerebrovascular degeneration and Alzheimer’s disease.
The research, which brought together scientists from UCD and the University of California, San Francisco, would not have been possible if patients had not donated their brains for research. All participants showed signs of memory loss prior to death, researchers said, and some brains did not show signs of either Alzheimer’s disease or cerebrovascular disease.
DeCarli began an effort 15 years ago to get more people of color to donate their brains because he felt that research was hampered by an implicit bias because most brains came from non-Hispanic whites.
All of the participants were assessed annually prior to their deaths, receiving physical and neurological exams, and giving detailed health histories. The brains included in the study were from decedents who had autopsies between Jan. 1, 2000 and Jan. 14, 2017.
For this research, the UC researchers looked at 360 brains from non-Hispanic whites, 35 from blacks, and 28 from Hispanics. Dugger said she’s looking forward to doing more comprehensive analysis of the abnormalities in these brains and in those donated in future. For instance, she said, most research around stages of a disease has been based on white people, but she and other researchers at UC Davis want to know whether those criteria apply to all races and ethnicities.
“When you think of treating a disease, you’re probably just treating a small subset of people,” she said, “and also when you’re trying to make correlations and inferences, you don’t have that large swath of all the differences that make us so great....To really understand disease, we have to understand the depth as well as the breadth, and that’s what UC Davis has offered me.”
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