UH study: Diversity in dementia risk factors across ethnicities

Approximately 23% of Alzheimer’s and related dementia cases in individuals aged 65 and older can be linked to controllable risk factors such as diabetes and physical inactivity;  that percentage varies depending on race and ethnicity, according to new research from the University of Hawaiʻi Cancer Center. 

The study, published in the January 17 issue of Neurology, the medical journal of the American Academy of Neurology, emphasizes the urgent need to address modifiable factors that are most relevant to each ethnic population to lower the risk of these debilitating conditions.

“There is no cure for Alzheimer’s disease, so preventing or delaying this disease by reducing controllable risk factors is an urgent public health priority,” said study author and UH Cancer Center researcher Song-Yi Park, PhD.

Top contributing risk factors varied across demographics:

• Diabetes for Latinos, and also less education and low socioeconomic status
• Low socioeconomic status for Native Hawaiians, and also physical inactivity, and less education
• Low socioeconomic status for Blacks and also low social contact and high blood pressure
• Low socioeconomic status for Whites, and also smoking
• Physical inactivity for Japanese Americans and also diabetes

The study involved about 92,000 participants from the Multiethnic Cohort Study (MEC), representing diverse racial and ethnic backgrounds, including Japanese American, White, Latino, Black, and Native Hawaiian. MEC is a large epidemiological study that follows more than 215,000 Hawaiʻi and Los Angeles residents for health diseases since 1993.

Participants completed detailed questionnaires covering education, medical history, medications, physical activity, sleep patterns, and dietary habits. The socioeconomic conditions of their neighborhoods were determined based on residential addresses. 

Disparities in diagnosed cases

After a nine-year follow-up on average, about 16,500 participants were diagnosed with Alzheimer’s or related dementia, with notable disparities among racial groups, particularly higher percentages among Black (24%) and Native Hawaiian (14%) participants.

Park highlighted the disparity among Native Hawaiians, previously not recognized because they are grouped with Asian Americans in research, although studies consistently show Asian Americans have the lowest risk for these conditions. The study observed that 12 controllable risk factors, together, explained about 23% of cases in both women and men. When additionally considering the strongest genetic risk factor, APOE ε4, researchers found that 31% of all cases could be attributed to known risk factors.

While the percentage of cases linked to controllable factors was similar among male and female participants, variations emerged in the percentage of cases linked to controllable factors when analyzing racial and ethnic groups. Controllable risk factors accounted for 33% of cases among Latinos, 29% among Native Hawaiians, 28% among Black individuals, 22% among White individuals, and 14% among Japanese Americans.

“Our findings confirm that less education, low socioeconomic status, and other risk factors in middle age account for substantial but varying proportions of dementia cases later in life across racial and ethnic populations,” said Park. “The study reveals the need for tailored interventions for various racial and ethnic groups, specific to more prevalent risk factors. It also highlights the importance of discovering other risk factors in racial and ethnic groups whose cases are not as well explained by known risk factors.”

The study acknowledged limitations, such as insufficient data on other known risk factors like hearing loss not treated with hearing aids, depression, traumatic brain injury, or exposure to air pollution.

The study was funded by the National Cancer Institute and the National Institute on Aging at the National Institutes of Health.