Dementia: First diversity study shows incidence highest in African-Americans, American Indians; rates falling overall

A first-of-its kind study of dementia risk among different populations in the United States has found African-Americans to have the highest incidence, while another shows U.S. dementia rates to be dropping as a whole.

The population study looked at data from 274,000 California residents divided into six racial and ethnic groups: Whites, Asian-Americans, Latinos, African-Americans, American Indians/Alaskan Natives and Pacific Islanders.

Results of the 14-year study showed an annual average rate of 26.6. cases of dementia per 1,000 people for African-Americans, followed by 22.2 cases per 1,000 people for American Indians/Alaskan Natives. Asian-Americans had the lowest incidence of dementia, with 15.2 annual cases per 1,000 people.

The data for the study came from Kaiser Permanente, one of Northern California's largest healthcare systems, meaning study subjects all had regular access to medical care, researchers noted. The study took other illnesses, such as cardiovascular disease, into account, but the racial and ethnic disparities remained.

"These findings underscore the need for further research to better understand risk factors for dementia throughout life to identify strategies to eliminate these inequalities," wrote lead researcher Elizabeth Rose Mayeda, Ph.D., a postdoctoral fellow at the University of California, San Francisco. Results of the study appear in Alzheimer's & Dementia: The Journal of the Alzheimer's Association.

A second study followed more than 5,000 residents of Framingham, MA, that have been tracked as part of a federally funded project since 1975.

That investigation showed an average 20% decrease in dementia risk over the study period, with the average age of people developing dementia raising from 80 in the late 1970s to 85 in recent years.

Education and improved heart health might have contributed to the drop in dementia risk, researchers noted. Those with at least a high school diploma showed a significant decrease in their risk for dementia.

The results were published in the the New England Journal of Medicine.