LONDON – The racial and ethnic patterns of dementia risk seen in older adults appear to hold steady even in the oldest old, with blacks about 30% more likely than are whites to develop the disorder even well into their 90s.
The magnitude of disparity remained consistent even after researchers controlled for traditional risk factors such as access to health care, cardiovascular risk, stroke, and education, Maria Corrada, ScD, said at the Alzheimer’s Association International Conference.
“These are the first estimates of dementia in a diverse cohort of subjects 90 years or older,” said Dr. Corrada, a professor of epidemiology at the University of California, Irvine. “The racial and ethnic differences in dementia incidence didn’t appear to be due to these factors that we have come to expect. These estimates can provide us with an important foundation for understanding the burden of racial disparities in the oldest old, which is the fastest-growing segment of our population in the U.S. and in many other countries.”
Dr. Maria Corrada
Most of the cohort (72%) was white; blacks comprised 16%, Latinos 4%, and Asians 7%. Not surprisingly, most were women (65%). The mean age at baseline was 93 years. Overall, 50% had at least a high school education, but that percentage was higher in whites (56%) and lower in blacks and Latinos (33% and 24%, respectively).
Midlife obesity was present in 42% overall, but this was significantly higher in blacks and Latinos (63%), and lower in whites and Asians (38% and 24%). Midlife hypertension was present in 38% overall. This was highest in blacks (63%), followed by Latinos (42%) and whites (35%). Only 7% of Asians had high blood pressure in midlife. About 40% of each group had experienced a late-life stroke, with the exception of Asians, with a stroke incidence of just 7%. Diabetes was present in 24% overall, in 20% of whites, and about a third of the other groups.
Over the follow-up period, dementia developed in 33% of subjects, at a mean age of 95 years, which did not vary among groups. The incidence of dementia was lowest in whites (32%) and Asians (31%). It was most frequent in blacks (39%), followed by Latinos (35%). The age-adjusted, 5-year incidence rate was 10% overall. It was lowest in Asians (9%) and whites (9.7%), followed by Latinos (10.6%); it was highest in blacks (12%).
Dr. Corrada then conducted a series of five multivariate regression analyses to examine the effect of various risk factors on dementia. The first three controlled for age alone; for age and education; and for age, education, and midlife risk factors of obesity, hypertension, and cholesterol levels. In every model, blacks were 30% more likely to develop dementia over the follow-up period than were whites. Model 4 controlled for age, education, and the late-life risk factors of stroke, depression, ischemic heart disease, heart failure, and heart attack. Model 5 controlled for age, education, and both the late- and midlife risk factors.
Again, no matter which model was used, blacks faced the same 30% increased risk, compared with whites. “The differences remained very consistent,” Dr. Corrada said. “The patterns of racial and ethnic disparity seen in younger elderly continued well after age 90.”
Dr. Corrada had no financial conflicts of interest.
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