In what is believed to be the largest study to date on race and dementia, researchers from UC San Francisco and the San Francisco Veterans Affairs Health Care System tracked health and demographic data from close to two million veterans. It compared rates of dementia across five racial groups and showed significant race-based variations in the incidence of the condition.
This study is also believed to be the first to report the rate of dementia in Native Americans using a nationwide sample, the researchers stated in their paper, publishing in JAMA on April 19.
Of the 1.87 million veterans, whose average age was 69, 88.6% were white, 9.5% were Black, 1% Hispanic, 0.5% Asian and 0.4% Native American. Just 2.3% were female, consistent with the gender distribution of the older veteran population. All received their health care at medical centers of the Veterans Health Administration (VHA) located throughout the continental United States.
Among the 13% of participants who were diagnosed with dementia over the course of the 10-year study, the researchers found that rates were markedly higher for Hispanic and Black veterans than they were for whites: 99% and 55% respectively. These results reinforce previous research that shows elevated rates for both groups.
Rates for Asian veterans have not been as widely documented and in this study were 24% higher than for whites. Among Native Americans, the rate was 8% higher than for whites, a finding that enhances prior research that has focused on smaller, geographically limited populations and has shown conflicting results, according to the researchers.
When adjusting for sex, education, and underlying medical and psychiatric conditions, differences in dementia rates for all four groups were narrowed slightly in relation to whites: 92% higher for Hispanics, 54% for Blacks, 20% for Asians and 5% for Native Americans. This finding for Native Americans shows no significant difference with whites, the researchers noted.
Senior author Kristine Yaffe, MD, of the UCSF Departments of Psychiatry and Behavioral Sciences, Neurology, Epidemiology and the San Francisco Veterans Affairs Health Care System, said she had been surprised by the relatively low risk for Native Americans. “There may be genetic or resilience factors that we just don’t know about yet,” she said, “or maybe even a survival bias. Those who are old enough to get dementia may have a survival advantage.”
Risk for Dementia Due to TBI, PTSD, Poor Cardiovascular Health
Yaffe said the study was unique in that it evaluated racial differences among five groups, versus two or three in previous studies, and that the cohort received their health care at the VHA, the largest integrated care system in the United States.
“U.S. veterans are at high risk of dementia because of exposure to military-related risk factors, like traumatic brain injury and post-traumatic stress disorder, and high prevalence of cardiovascular and other non-military risk factors,” she said.
As expected, health and education disparities associated with dementia were more apparent in some groups. Native Americans were least likely to live in ZIP codes where more than 25% of residents were college-educated (26.9%), and had the highest rate of obesity (16.4%), post-traumatic stress disorder (11.2%) and alcohol use disorder (9.1%). Hispanics had the highest rate of diabetes (36.1%) and stroke (8.2%), and Blacks had the highest rate of hypertension (73.7%).
The researchers found regional variations in dementia incidence, but Black and Hispanic veterans were consistently identified as having higher risk than the other groups.
These racial and ethnic differences are concerning, said first author Erica Kornblith, PhD, of the UCSF Department of Psychiatry and Behavioral Sciences, and the San Francisco Veterans Affairs Health Care System, “but they underscore the need to explore the cause of these differences with the ultimate goal of ameliorating them.”
Differences in Dementia Diagnosis May Reflect Biases of Doctors
Differences in dementia diagnosis may also reflect “the biases of doctors who make the diagnosis or biases in our cognitive tests, as well as the impact of education, and medical and psychiatric variables,” Kornblith said.
Since most veterans serve as young adults and remain eligible for health care for the rest of their lives, it is likely that the participants had more equitable access than that of the general population, the researchers noted.
“This implies other mechanisms may be at play, such as early life circumstances, or that there were differences in quality of health care, despite better access,” said Yaffe, who is also affiliated with the UCSF Weill Institute for Neurosciences and the Northern California Institute for Research and Education. “In future studies, we hope to have a better understanding of the mechanisms that are driving the differences in dementia incidence across these five groups,” she said.
Co-Authors: Amber Bahorik, PhD, of UCSF and Northern California Institute for Research and Education; Feng Xia, MPH, of San Francisco VA Health Care System and Northern California Institute for Research and Education; Deborah E. Barnes, PhD, MPH, and W. John Boscardin, PhD, of San Francisco VA Health Care System and UCSF.
Funding: This study was supported by Department of Veterans Affairs Rehabilitation Research and Development Career Development Award (CDA-2) 1 IK2 RX003073-01A2 (Kornblith) and NIA grant K24 AG031155, R35 AG071916 (Yaffe).