The reason why is still unclear.
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"There's not enough statistics. We don't know. Is it lifestyle? Is it environment? Is it socio-economic?" said Hadi Finerty, of the Alzheimer's Association - Illinois chapter.
Experts say contributing factors can be high blood pressure and diabetes, but with so few black people participating in clinical research studies, it's hard to determine what's playing a role.
Lynn Watkins-Asiyanbi's mother was physically healthy when she noticed she was having trouble remembering things.
Her mother was diagnosed with Alzheimer's at age 77, and died recently at 82-years-old.
"It's the most horrible disease ever for someone to live through and live with," Watkins-Asiyanbi said.
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Watkins-Asiyanbi, a Chicago attorney, said her mother's death has been difficult. Her parents were married over five decades and her 85-year-old dad is still struggling with the loss.
"It's a family disease because it doesn't not only impact one person, it impacts the entire family," she said.
Now, Watkins-Asiyanbi worries that the brain disease could also affect her someday.
"It is what it is. God's fate is what he has planned for us already," she said.