Early life experiences, such as childhood socioeconomic status and literacy, may have greater influence on the risk of cognitive impairment later in life than demographic characteristics such as race and ethnicity, according to new research.
The new study from researchers at the University of California Davis Alzheimer’s Disease Center and the University of Victoria, Canada, challenges earlier research that suggests a link between race and ethnicity, particularly among Latinos, and an increased risk of cognitive impairment and dementia later in life.
“Declining cognitive function in older adults is a major personal and public health concern,” said Bruce Reed, a professor of neurology and associate director of the University of California Davis Alzheimer’s Disease Center.
“But not all people lose cognitive function, and understanding the remarkable variability in cognitive trajectories as people age is of critical importance for prevention, treatment, and planning to promote successful cognitive aging and minimize problems associated with cognitive decline.”
For their research, the scientists recruited more than 300 men and women, all 60 years old or older. Recruited from senior citizen recreational and residential centers, as well as churches and health-care settings, the seniors had no major psychiatric illnesses or life threatening medical illnesses. Participants were Caucasian, African-American, or Hispanic and spoke either English or Spanish.
Testing included multidisciplinary diagnostic evaluations through the University of California Davis Alzheimer’s Disease Center in either English or Spanish, according to the researchers.
Consistent with previous research, the study found that non-Latino Caucasians scored 20 to 25 percent higher on tests of semantic memory — general knowledge — and 13 to 15 percent higher on tests of executive functioning compared to the other ethnic groups.
However, ethnic differences in executive functioning disappeared and differences in semantic memory were reduced by 20 to 30 percent when group differences in childhood socioeconomic status, adult literacy, and the extent of physical activity during adulthood were considered, the researchers discovered.
“This study is unusual in that it examines how many different life experiences affect cognitive decline in late life,” said Dan Mungas, professor of neurology and associate director of the University of California Davis Alzheimer’s Disease Research Center.
“It shows that variables like ethnicity and years of education that influence cognitive test scores in a single evaluation are not associated with rate of cognitive decline, but that specific life experiences like level of reading attainment and intellectually stimulating activities are predictive of the rate of late-life cognitive decline. This suggests that intellectual stimulation throughout the life span can reduce cognitive decline in old age.”
Regardless of ethnicity, advanced age, and apolipoprotein-E (APOE genotype) were associated with increased cognitive decline over the four years the participants were followed. APOE is the largest known genetic risk factor for late-onset Alzheimer’s, according to the researchers.
Less decline was experienced by people who reported more engagement in recreational activities in late life and who maintained their levels of activity from middle age to old age, the researchers found.
Single-word reading — the ability to decode a word on sight, which often is considered an indication of quality of educational experience — was also associated with less cognitive decline, a finding that was true for both English and Spanish readers, irrespective of their race or ethnicity, according to the study. These findings suggest that early life experiences affect late-life cognition indirectly, through literacy and late-life recreational pursuits, the researchers said.
“These findings are important, because it challenges earlier research that suggests associations between race and ethnicity, particularly among Latinos, and an increased risk of late-life cognitive impairment and dementia,” explained Paul Brewster, lead author of the study, a doctoral student at the University of Victoria, Canada, and a pre-doctoral psychology intern at the University of California San Diego Department of Psychiatry.
“Our findings suggest that the influences of demographic factors on late-life cognition may be reflective of broader socioeconomic factors, such as educational opportunity and related differences in physical and mental activity across the life span.”
The study, “Life Experiences and Demographic Influences on Cognitive Function in Older Adults,” was published in Neuropsychology, a journal of the American Psychological Association.