The first study to look at dementia risk in a population representing the diversity of the United States finds dementia incidence to be highest in African Americans and lowest in Asian Americans. The rate of occurrence of dementia in African Americans was found to be 65 percent higher than Asian Americans. The results are published online today by Alzheimer's & Dementia: The Journal of the Alzheimer's Association.
The study population included more than 274,000 members of Kaiser Permanente – a large, integrated healthcare delivery system in Northern California. The scientists compared dementia incidence across six racial and ethnic groups – Whites, Asian-Americans, Latinos, African Americans, American Indians/Alaskan Natives, and Pacific Islanders.
"Most research on disparities in dementia includes only one to two racial and ethnic groups, for example only Whites and African Americans," said study first author Elizabeth Rose Mayeda, Ph.D., Postdoctoral Fellow at University of California, San Francisco in the Department of Epidemiology and Biostatistics. "Our study is the only work that compares dementia for these six racial and ethnic groups representing the aging demographic of the United States in a single study population. It is also the first study to look at incidence of dementia in Pacific Islanders and American Indians."
The researchers used electronic health records covering medical visits from January 2000 through December 2013 to identify individuals diagnosed with dementia, and race and ethnicity information in the healthcare system's member database to categorize participants into the six groups. The dementia diagnoses were either Alzheimer's, vascular dementia, or non-specific dementia.
The researchers found that dementia incidence over the 14-year study period ranged from an average annual rate of 26.6 cases of dementia per 1,000 people for African-Americans, and 22.2 cases per 1,000 people for American Indians/Alaskan Natives, to 15.2 cases per 1,000 people for Asian-Americans. In between were Latinos and Pacific Islanders with an average annual rate of 19.6 cases per 1,000 people, and whites with 19.3 per 1,000.
As members of the same healthcare system, all study participants had regular access to medical care during the study period. Despite this, and after the researchers accounted for other illnesses, such as cardiovascular disease, the disparities in dementia incidence 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," said Dr. Mayeda.
Using the observed dementia incidence rates and a widely accepted method of calculating a person's lifetime risk for developing a disease, the researchers estimated the percentage of individuals free of dementia before age 65 in each racial and ethnic group who can expect to be diagnosed with dementia over the next 25 years. The projections were 38 percent of African Americans, 35 percent of American Indians/Alaskan Natives, 32 percent of Latinos, 25 percent of Pacific Islanders, 30 percent of Whites, and 28 percent of Asian Americans.
"Even in the lowest risk groups in the study, the lifetime risk of developing dementia is high," said study senior author Rachel Whitmer, Ph.D., Epidemiologist at Kaiser Permanente Northern California, Division of Research. "Our projections indicate that in every racial and ethnic group, over one in four people who survive to age 65 can expect to be diagnosed with dementia in their lifetime."
"As the authors point out, the findings demonstrate major inequalities in dementia incidence in a group of people who had regular and equal access to health care during the study period. This helps us understand the progress that needs to be made to effectively reduce these disparities," said Keith Fargo, Ph.D., Alzheimer's Association Director of Scientific Programs & Outreach. "In fact, reducing disparities in Alzheimer's for minority populations is identified as a priority by the National Plan to Address Alzheimer's Disease. To achieve this goal, we need to understand why the risk for Alzheimer's and dementia is different among ethnic and racial groups. This is an important area of research for the Alzheimer's Association."
The Alzheimer's Association has provided $22.9 million for 131 studies over the past 23 years to better understand disparities in Alzheimer's and dementia in ethnic and racial groups and the impact of lifestyle factors on risk for cognitive decline and dementia. With the Alzheimer's Association's support, the United States created the National Plan to Address Alzheimer's Disease in 2012. The plan includes the critical goal of preventing and effectively treating Alzheimer's by 2025.