Dementia afflicts black people and American Indians more than other racial groups in the U.S., according to a recent study highlighting dramatic disparities in the prevalence of the disease.
Researchers looked at six different racial and ethnic groups - African Americans, American Indians and Alaska natives, Hispanics, Pacific islanders, Asian Americans and whites.
Dementia rates varied widely, with blacks 65 percent more likely to develop the disorder than Asian Americans, the study found.
"The fact that our heterogeneous groups of Asian Americans as a whole had a markedly lower risk is illuminating and speaks to the fact that we need to understand why so we can help lower the risk for everyone," said senior study author Dr. Rachel Whitmer, an epidemiologist with Kaiser Permanente and the University of California, San Francisco.
If every person age 65 and older in the U.S. had the same risk of dementia as Asian Americans, that could avert 190,000 cases every year, Whitmer added by email.
To explore the connection between race and dementia, Whitmer and colleagues analyzed data on 274,000 members of Kaiser Permanente - a large integrated insurance, hospital and clinic organization based in Northern California.
The researchers tracked dementia incidence from 2000 through 2013 for people aged 60 and up, and they also estimated cumulative 25-year risk of developing the disorder after age 65.
Over the 14-year study period, all of the patients had equal access to health care, so a lack of insurance coverage or an inability to find doctors that accepted their benefits could not explain any of the disparities in dementia rates, the authors note in the journal Alzheimer's and Dementia.
At the start of the study, people were 73 years old on average and most had at least one annual healthcare visit.
During the study, almost 60,000 people developed dementia, while about 89,000 did not. An additional 80,000 people died, and about 46,000 left the Kaiser Permanente system.
The dementia risk was highest for African-Americans, with a rate of about 27 cases per 1,000 people per year, followed by about 22 cases per 1,000 per year for American Indians and Alaska natives.
Latinos and Pacific Islanders had an incidence of about 20 cases per 1,000 people per year and whites had about 19 cases per 1,000 per year.
Asian-Americans had the lowest risk, with an incidence of just 15 cases per 1,000 people per year.
Researchers also calculated the cumulative 25-year dementia risk and estimated 38 percent of blacks would develop the disease, compared with 35 percent of American Indians and Alaska natives, 32 percent of Latinos and 30 percent of whites. Pacific Islanders had a 25 percent cumulative risk and Asian-Americas had a 28 percent cumulative risk.
One shortcoming of the study is that it relied on medical records with a clinical diagnosis of dementia but lacked brain imaging or postmortem pathology to confirm the diagnosis or to distinguish between Alzheimer's disease and so-called vascular dementia, the authors note.
Researchers also lacked information about patients' education levels and other socioeconomic factors that could influence dementia risk.
Even so, the study is one of the largest to examine racial and ethnic disparities in dementia diagnoses and should provide a benchmark for efforts to reduce these inequities, said Jennifer Manly, of the Taub Institute for Research on Alzheimer's Disease and the Aging Brain at Columbia University in New York.
"There are huge disparities in dementia that are confronting this nation and this will translate into an enormous burden on families if we don't address this," Manly, who wasn't involved in the study, added by email. "We need to prioritize research that uncovers the reasons for these disparities and more research should include racially and ethnically diverse people."
In the meantime, there are steps people can take to maintain a healthy brain while they age, said Annette Fitzpatrick, a public health researcher at the University of Washington in Seattle who wasn't involved in the study.
"Exercise of both the mind and body are beneficial for the entire person's well-being across the years - for younger persons as well as older adults," Fitzpatrick said by email. "And while we still have not untangled the types of 'brain games' or exercises that are best, any activity of this sort cannot hurt."