, included a group of more than 22,000 patients aged 60 or older who were members of the Kaiser Permanente Northern California Diabetes Registry. Dementia was diagnosed in 3,796 patients (17.1 percent of the study cohort) during a follow-up of up to 10 years. Dementia was not present in any of the patients at the start of the study.
Compared to Asian-Americans, Native Americans were 64 percent more likely to develop dementia, and African-Americans were 44 percent more likely. Almost 20 percent (or one in five) African-Americans and Native Americans were diagnosed with dementia during the 10-year study.
"We found that in a population of elderly individuals with type 2 diabetes, there were marked differences in rates of dementia over a 10-year period by racial and ethnic groups," said senior author Rachel Whitmer, PhD, research scientist at the Kaiser Permanente Division of Research. "Moreover, the differences were not explained by diabetes-related complications, glycemic control or duration of diabetes. Nor were they altered by factors of age, gender, neighborhood deprivation index, body mass index, or hypertension."
Among people aged 60 and above, those with type 2 diabetes have double the risk of developing dementia. Certain racial and ethnic groups in the U.S., including Latinos, African-Americans, some Asian American groups, and Native Americans, are disproportionally affected by type 2 diabetes. However, the interplay of type 2 diabetes and race/ethnicity on long-term dementia risk has not been explored previously.
"Since ethnic minorities are the fastest-growing segment of the elderly population in the United States, it is critical to determine if they are at higher risk of dementia, especially among those with type 2 diabetes," said Elizabeth Rose Mayeda, PhD, lead author and postdoctoral fellow at University of California San Francisco. "It's eye-opening to see the magnitude of ethnic and racial differences in dementia risk in a study where everyone already has type 2 diabetes."
The researchers concluded that more work is needed to identify factors that will reduce dementia risk for those with diabetes, particularly for ethnic and minority groups at highest risk. While future research is greatly needed on potential dementia prevention efforts in general, these findings suggest that certain ethnic groups within the type 2 diabetes population may benefit the most.
This study is part of an ongoing body of work to better understand dementia. Earlier this year, Kaiser Permanente researchers created the first risk score that predicts the 10-year individualized dementia risk for patients with type 2 diabetes.