Studies explore Alzheimer's risk factors, biomarkers in Latinos
Most people have a greater chance of developing Alzheimer’s disease as they age. For Latinos—the fastest-growing group of older adults in the United States—some risk factors seem to matter more than for other groups.
The Centers for Disease Control and Prevention (CDC) reports that by 2060 the number of Latinos age 65 and older is expected to nearly quadruple, and Latinos will face the largest increase in Alzheimer’s disease and related dementias cases of any racial/ethnic group in the United States. Because aging is the greatest risk factor for Alzheimer’s, that means more Latinos with the disease in the years ahead—about 3.5 million in the United States by 2060.
Beyond age, certain factors may put some Latinos at increased risk, including low socioeconomic status, lots of cardiovascular disease, and a higher prevalence of conditions like diabetes, high blood pressure, obesity, and depression. Latinos also tend to develop symptoms at a younger age than non-Latino whites.
NIA supports studies to identify these risk factors—and use that information to improve Latinos’ odds against Alzheimer’s.
“Population-based studies will help us to understand health and risk factors in specific groups, including Latinos,” said Dallas Anderson, Ph.D., program officer at NIA’s Division of Neuroscience. “Ultimately, the goal is to identify targeted ways to prevent and diagnose disease early.”
Exploring risk and protective factors
The NIA-supported Study of Latinos-Investigation of Neurocognitive Aging (SOL-INCA) is looking at mild cognitive impairment (MCI) in middle-aged and older Latinos and conditions, such as cardiovascular and genetic risk factors, that could contribute to MCI, a common precursor of Alzheimer’s. A unique aspect of the study is the diversity of its participants, who include people of Cuban, Puerto Rican, Dominican, Mexican, Central American, and South American origins.
The study draws on the Hispanic Community Health Study/Study of Latinos, which collected information on heart and lung diseases, cognitive health, and genetic profiles of more than 16,000 participants in four cities (New York, Chicago, Miami, and San Diego). As part of SOL-INCA, researchers led by Hector M. González, Ph.D., co-director of the Latino Core of the University of California, San Diego’s Shiley-Marcos Alzheimer’s Disease Research Center, are comparing health data—from diabetes, blood pressure, neurocognitive, and other tests—from almost 10,000 participants, ages 50 to 80, with data collected from those same participants 6 years later.
Emerging findings show strong relationships between lower cognitive function and diabetes, high blood pressure, and other cardiovascular disease risk factors, said Dr. González. “Having various vascular-disease risk factors seems to accelerate cognitive decline in Latinos even more than for non-Hispanic whites. We’d like to understand why,” he said.
NIA funding will allow researchers to add magnetic resonance imaging (MRI) to the study to help characterize how cardiovascular risk factors and genetic variants contribute to Alzheimer’s and vascular pathology in the brain. “We’ll get a snapshot, literally, of participants’ brains and can see how their vascular and genomic risks relate to their brain structural status,” Dr. González said.
The MRI component of SOL-INCA is being co-led by Charles DeCarli, M.D., director of the Alzheimer’s Disease Center at the University of California, Davis. Other participating institutions include Albert Einstein College of Medicine, University of Illinois, University of Miami, San Diego State University, University of North Carolina, University of Texas Science Center, and Wayne State University.
Identifying early Alzheimer’s biomarkers
In addition to SOL-INCA, NIA supports studies that aim to find out whether Latinos have distinct biomarkers (biological signs of disease) that affect their development of Alzheimer’s, and if and how these biomarkers differ from those in other racial/ethnic groups.
For example, a population-based study at the University of North Texas Health Science Center is studying Mexican-Americans age 50 and older. “Our study is trying to identify novel and altered biological mechanisms of disease that may be expressed differently among Latinos or more prevalent among Latinos,” said lead investigator Sid O’Bryant, Ph.D. “We want to find out how these biological mechanisms are impacted by the health disparities of increased rates of depression and diabetes.”
The 5-year study involves 1,000 Mexican-Americans and 1,000 non-Hispanic whites in north Texas. Participants with normal cognition, MCI, or Alzheimer’s disease will undergo a detailed interview, functional exam, brain imaging, cognitive testing, and blood work at two visits.
Previous research shows that Alzheimer’s disease biomarkers for Mexican-Americans could differ from biomarkers for non-Hispanic whites, Dr. O’Bryant said. “When you look at proteomic profiles side-by-side, among non-Hispanic whites, the profile of Alzheimer’s disease is more inflammatory and vascular in nature,” he said. “Among Mexican-Americans, we find a more metabolically driven profile.” In other words, medical conditions related to diabetes may be more powerful drivers of memory loss during the aging process among Mexican-Americans.
Dr. O’Bryant added, “Understanding this is important, as this would rapidly identify possible interventions to be tested in clinical trials.”
Another study, based at Columbia University, also seeks to identify and compare biological (as well as cultural) differences in Alzheimer’s risk between Latinos and other racial/ethnic groups. Led by Jennifer Manly, Ph.D., the study is looking at 3,000 middle-aged adults, some of whose parents have Alzheimer’s disease. Dr. Manly hypothesizes that Alzheimer’s risk in Latinos (and African Americans) is driven more by vascular and social pathways than by the genetic pathways seen in whites.
A related study, led by Adam Brickman, Ph.D., will use positron emission tomography (PET) scans to examine tau, a protein that forms toxic tangles inside neurons in the Alzheimer’s brain, in 150 of Dr. Manly’s study participants. Researchers want to determine if tau deposition is related to cognitive function in midlife and if there are differences among racial/ethnic groups. They also want to see if tau is linked to markers of cerebrovascular disease in the brain, which may vary among racial/ethnic groups.
Moving toward better prevention and diagnosis
Recent research indicates a decline in U.S. dementia rates, suggesting that certain lifestyle factors, such as controlling high blood pressure, are making a difference from one generation to the next, said Dr. Anderson. That’s promising evidence that people can make changes that might reduce their risk of Alzheimer’s disease or other types of cognitive impairment. Further research may help pinpoint which changes can have the greatest impact for specific populations.
“The ultimate goal is to look for ways that we may prevent cognitive decline and disorders,” said Dr. González. “For example, if we see there are some strong vascular contributions to cognitive impairment and mild cognitive impairment, that’s bad news. But the good news is that you can do something about that by improving cardiovascular health.”
Drs. González and O’Bryant have designed their studies so data can be pooled to provide a larger group that includes Latinos of diverse backgrounds. Other researchers will have access to the data, which could help expand research in Latino and other populations.
“The one-size-fits-all approach for Alzheimer’s disease just isn’t going to be the long-term solution,” Dr. O’Bryant said. “In the long run, to be effective, we will need population-specific approaches to diagnose and treat Alzheimer’s disease that recognize differences in biological and lifestyle risk factors.
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