Black and Latino people experience higher rates of Alzheimer's disease and related dementias than non-Hispanic white people, but scientists have never known why. Now a new study shows that experiences with discrimination may be playing a role in disproportionate experiences of cognitive decline.
In a first-of-its-kind study, published recently in the journal Social Science & Medicine, researchers from The University of Texas at Austin, University of California, Davis and Florida State University examined 1,100 people between the ages of 23 and 62 living in the United States. Most of the study participants were born in Mexico, and all of them identified as Latino and/or Hispanic. Participants were followed for 12 years and were asked about their experiences with perceived discrimination. Researchers also evaluated the participants' cognitive function and found those who had reported experiencing more discrimination throughout the study were more likely to have poorer cognitive performance at the end of the study.
"It is critical that we identify modifiable risk factors for cognitive decline and impairment," said Elizabeth Muñoz, assistant professor of human development and family sciences at UT Austin and lead author of the study. "This study shows that experiencing discrimination because of one's ethnic group or where they were born is a risk factor."
Previous studies have found higher rates of cognitive decline in minority populations, such as Black and Latino people, when compared with white people. Other research found associations between discrimination and cognitive impairment in Black adults. This study is the first to link discrimination to cognitive decline in Latino adults.
Researchers in the study identified differences among study participants along two different trajectories of experiences of discrimination. One group, identified as Stable Low, experienced lower levels of discrimination but at stable levels over time. Another group was identified as High Declining, experiencing higher levels of discrimination at the beginning of the study and declining over time. The Stable Low group scored better cognitively than those in the High Decline group, who were more likely to suffer impairment.
At the beginning of the study, 74% of participants reported experiencing discrimination sometimes or more often. By the end of the study, 47% of participants reported the same thing, showing that experiences of discrimination declined over time. Researchers controlled for age, education level, baseline IQ scores and language preference.
The study found that those participants who were born in the United States were more likely to be in the High Declining group and more likely to experience cognitive impairment, while those who were born in another country and immigrated were more likely to be in the Stable Low group and less likely to experience cognitive impairment.
"It's not clear why there appears to be a somewhat protective effect for immigrants," Muñoz said. "Previous research has shown that acculturation is a risk factor for discrimination. Those born in the United States may be occupying more traditionally white spaces and may encounter discrimination there. It may be that immigrants stick closer to communities of other immigrants. There is a resilience factor among immigrants that deserves further study."
Richard W. Robins of the University of California, Davis and Angelina R. Sutin of Florida State University also contributed to the research. The research was funded by the National Institutes of Health, the Center on Aging and Population Sciences at The University of Texas at Austin, the National Institute on Aging, the Population Research Center at The University of Texas at Austin and the Eunice Kennedy Shriver National Institute of Child Health and Human Development.
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